1. Support students to develop a critical sense of curiosity about scientific endeavours.
2. Prepare students to critically address science-related socio-economic and environmental issues.
3. Provide students with the foundation in science to prepare them for higher levels of study and science-related careers.
4. Enable students to use science and technology to think about how to solve everyday problems so that they may improve the quality of their own lives and the lives of others.
Biological diversity refers to the number and variety of species and ecosystems on the Earth and the ecological processes of they are a part of. This should be differentiated from Earth's biodiversity, which is the entire collection of living organisms, each with their own unique characteristics.
A Species is a group of organisms that the same structures (characteristics) and can reproduce with each other (interbreed). There are over 1.5 million species of animals and 350,000 plant species identified so far.
The main components of biodiversity include:
Genetic diversity – occurs within organisms at a cellular level, as it describes the variety of genetic material in all living things.
Variations result in varying abilities for different organisms to survive in specific environments. This is called Adaptation. There are two types of adaptations. Physical features of an organism are structural adaptations, whereas, actions are behavioral adaptations.
In most ecosystems, resources such as water, food, sunlight, space, are scarce and so several species have to compete for these resources. The competition is not fair because one species may be better able to obtain the resource than another species. The species that is better able to obtain resources (outcompetes the other species) is at an advantage over other species resulting in better chances for survival. The species who does not win the resource may have to switch to a different, less desirable resource in order to survive.
To measure the biological diversity of an area, biologists use a measurement called a diversity index. This compares the diversity of species in a certain area with the total number of organisms in that same area, or ecosystem. The index is used to assess the health of an ecosystem, where a higher index indicates a healthier ecosystem.
A habitat is the natural home or environment of an animal, plant, or other organism.
On the other hand, a niche is the role an organism has within a particular habitat or ecosystem. An organism's niche can be defined by describing what the organism eats, What eats the organism, physical description of its habitat, Nesting site, range and habits, What effect it has on the other populations, What effect it has on the environment etc. An organism's niche can change, depending on the environment in which it is located and the organisms with which it inter-relates.
Broad Niche: An organism that is adapted to an extensive range of environmental conditions for survival is said to have a broad niche. This wide range of adaption and survival skills indicates that the organism can live in various different conditions. The reverse side of this would be a narrow niche, in which the organism must have very specific environmental conditions to survive and only plays a limited role in its habitat. A broad niche organism may also be called a generalist, while a narrow niche organism may be called a specialist.
In the tropics, where the temperatures are relatively constant and food supply is stable, organisms are specialists. They efficiently survive in their environment, because they have relatively narrow niches with adaptations directed toward competing for one dependable food source, type of soil or level of light. This specialization allows many different species to coexist in the same area, preventing one species from becoming dominant. The result of this is high diversity with low populations. A specialist is well adapted to survive in one particular environment. This is considered to be the ‘trap of specialization’, because, as it is able to survive very well in one environment, it is not able to adapt to extreme change and may not survive when this occurs.
Some organisms have adaptations that enable them to live in extreme environments. These are called Extremophiles. These environments might have high pressure, high (or low) temperature, high radiation levels, high pH etc. Examples include: Antarctic springtail are arthrods that live in extreme cold, by producing a kind of antifreeze in its tissues, Tube worms live on the ocean floor, near black smokers, where volcanic vents make the temperature extremely hot etc.
The simplest means of reproduction is Asexual reproduction. This is the production of new organisms from one parent. The offspring is identical to the parent. Asexual reproduction can be an advantage because it enables organisms to increase in numbers quickly.
There are several types of asexual reproduction. In some cases, it is a simple mitosis such as binary fission in bacteria. In other cases, it involves a process called budding. Budding occurs when an outgrowth (a bud) develops as a product of increased cell division. Eventually the bud can break off and develop into a new organism. In some cases (such as sea stars), a piece that breaks off can grow into a new organism in a process called regeneration. Some plants especially the grass family can grow new stems from underground roots. These stems can grow into complete plants.
Sexual reproduction occurs in the more complex animals and usually involves the fusion of two cells (gametes) in a process called fertilization. Fertilization can either occur inside the female body (internal fertilization) or outside the female body (external fertilization). Most fish and amphibians utilize external fertilization. Reptiles, bords and mammals utilize internal fertilization. The fusion of the gametes results in the formation of a zygote, which divides through mitosis eventually forming a new organism.
Reproduction can either be classified as sexual or asexual. Sexual reproduction is the production of new organisms by the union of a male and female sex cells. Asexual reproduction is the production of a new organism using only one cell type. Some organisms can reproduce through both sexual and asexual processes.
Sexual reproduction in plants involves gametes as well, male gametes and female gametes joining, during fertilization, to produce a zygote and then an embryo. Pollen contains the male gametes and is found on the stamen. Ovules contain the female gametes and are found in the pistil. Pollination occurs when pollen is transferred from the anther of the stamen to the stigma of the pistil. Cross-pollination occurs when pollen from one plant is carried to the stigma of another plant by wind, water or animals (bees or butterflies). Cross fertilization occurs when a grain of the pollen forms a long tube (pollen tube), which grows down the style into the ovary. The gametes unite to produce a zygote, which then develops into an embryo. This usually happens inside a seed, which protects the embryo and provides food (cotyledon) for the embryo when growing conditions are right. Plants which are produced, as a result of cross-fertilization, are not identical to either plant.
Seeds: A seed is a structure that contains a young developing plantand stored food. Under suitable environmental conditions, the seed will grow into a new plant. Seed plants reproduce by sexual reproduction. The male sex cell is called a sperm, and it must unite with the femaile sex cell called the egg. Sperm cells are located within pollen grains, which are produced in the anther of the flower. Eggs are located in the flower's ovary. The ovary is located at the bottom of the stigma. The transfer of pollen from the anther to the stigma is called pollination. The transfer results in the union of male and female sex cells. This union is called fertilization and results in the formation of a viable seed.
Self pollination occurs when pollen is transferred from the anthers to the stigma on the same flower. Cross pollination is when the pollen is transferred to the stigma of a different flower. Pollinators are organisms that transfer pollen from flower to flower, such as bees, butterflies, birds etc.
Seeds need to be transferred from the parent plant/tree so that they can grow in a different area not too close from the parent. This process is called Seed dispersal. Some seeds are light and can be blown away by wind. Other seeds stick on animal fur and are carried by the animals to distant locations. Some other seeds are eaten by animals but not digested so the animal poops the undigested seed at a different location.
Some plants use spores instead of seeds. Spores are cells that can develop into new organisms. Spores do not contain stored food. Mosses and ferns use spores to reproduce.
Bacterial Conjugation: Bacteria are able to transfer genetic material directly from one cell to another through a process called bacterial conjugation. It is a primitive form of sexual reproduction, since two parent cells are involved. The benefit is that new combinations of inherited characteristics may result. Although this process is not actually reproduction, because there is no increase in the number of cells, it does result in genetic recombination. The newly created cell can then divide by binary fission, to create identical cells with the new genetic material.
Sexual reproduction in animals also involves gametes. The male gametes are called sperm cells, and the female gametes are called egg cells (ova). During mating, the sperm cell and the egg cell unite in a process called fertilization to form a zygote. The zygote undergoes several series of cell divisions and specializations resulting in the development of an embryo. This embryo develops further into a multi-cellular organism. This occurs inside the uterus of the female or outside (in an egg shell) in other animals.
Living things usually tend to look like their parents. Parents pass some features (inherited traits) to their offspring. Inherited traits are characteristics that are passed from parent to offspirng. For example, eye color in humans is inherited from the parents. The passing of inherited traits from parents to offspring is called heredity. Inherited traits should be differentiated from acquired traits. Acquired traits are characteristics that are developed by an individual as they live and are influenced by the environment. For example, the ability to sign a complex song may be an acquired trait. Acquired traits are not passed on to offspring. For example, a heavy built weight-lifter does not produce heavily built children.
Purebred VS Hybrid: To produce purebred organisms, a breeder would choose pure bred parents, ie., those parents whose ancestors have produced only the desired characteristic they want (true-breeding). If a breeder chooses two different 'true-breeds' then a hybrid would be produced.
Dominant Traits: Crossbreeding two different true-breeds will result in all of the offspring having the same characteristic, that is, the dominant trait. Only the DNA instructions for the dominant trait will be expressed.
Recessive Traits: When crossbreeding hybrids, the average results will produce 75% of the offspring with the dominant trait and 25% of the offspring with the recessive trait, because there are only 4 possible combinations. One trait is recessive and therefore the allele is recessive. A recessive trait only appears in the offspring if two recessive alleles are inherited.
Let's express the height trait using the letter T. Every individual plant receives one form of the trait from the two parent plants. So the height trait is represented by two letters. Depending on the form of trait received from the parents, an individual can either be TT, Tt or tt. If the tall trait is dominant, then individuals with TT and Tt will be tall, and only the tt individual plants will be short.
To make a punnett square, create a table with 2 columns and 2 rows. On the left side, indicate the genes that came from the female. At the top, represent the genes that came from the male. Each parent's gene will combine to make pairs of genes in the offspring. These are represented inside the cells of the table as shown in the image alongside.
The probability is the likelihood of an event. However, it is not the actual distribution that will be observed, the actual observed distribution is usually close enough to the propability if you have large enough number of offspring. For example, when the two parents have the Tt genes, the punnett square shows that 25% of offspring will be TT, 50% will be Tt and 25% will be tt. If T is a dominant trait, then 75% of the offspring (TT and Tt) will look the same/will express the same trait. You could predict that there is a 25% chance that the offspring will be tt.
Not all characteristics are inherited, some characteristics develop depending on the environment the organism is exposed to. Examples include: change in the pigmentation of skin color throughout the seasons due to the sun, height and weight can be influenced by diet. Scars, injuries, clothing, hairstyle, makeup, and cosmetic surgery may change a person’s characteristics, but they are not caused by genetics. One way that scientists study the relationship between genetics and the environment is to observe the similarities and differences between identical twins that have been separated at birth and raised in different environments.
Factors in the environment, or random events can change genetic information contained in DNA. These changes are called mutations, and can cause changes in the structure of organisms, including people. Mutagens, such as X-rays, ultraviolet rays, cosmic rays and some chemicals can cause mutations to occur – some that have little visible effects and some that have dramatic effects. If mutations occur in the DNA of reproductive cells, the changes can be passed on from the parent to the offspring, increasing the variation within a species.
Compared to many scientific fields, which were studied way back in the 1700 and many discoveries were already made, the field of genetics is still new. Most discoveries were made after 1950 and because there were no technologies to allow more research, knowledge in the area did not expand significantly until the later 20th century and into the 21 century. This means there are new discoveries being published and the content of this website will be revised and updated as necessary.
DNA is short for Deoxyribonucleic acid. It was discovered in 1953 by James Watson and Francis Crick. The DNA molecule itself looks like a long spiral made up of two strands twisted together. This structure is called a double helix. Watson and Crick showed that each rung of the double helix was made up of a pair of chemicals called bases, and that there are 4 different bases present in DNA: Cytosine (C), Guanine (G), Thymine (T) and Adenine (A). The bases from the two strands interact with each other using weak bonds such that A bonds with T and G bonds with C. The sides of the double helix are made of sugars (deoxyribose) and phosphates.
The order of the basepairs in each strand is what determines genetic characteristics and that order is only spcific for that individual organism, no two organisms share the same order. There are many controls to ensure each gene is expressed correctly. For example, this ensures that corneal tissue develops only in of the cornea of the eye and nail tissue only grows at the tip of fingers and toes.
DNA also differs between species. The DNA of a particular species is specific to that species. All the DNA that makes up an individual is called the individual's genome. The human genome is made up of about 3 billion bases (base pairs). The variation in the number and order of these base pairs is responsible for all the variation we onserve in living organisms.
Genes are located in the chromosomes and come in pairs. Each chromosome has numerous gene locations. Both genes in a pair carry DNA instructions for the same thing. Specific characteristic genes occupy matching locations on the two chromosomes. DNA code may not be exactly the same in both locations. Offspring inherit genes from both parents. The genes exist in an array of possible forms that differ as to their exact DNA sequence. These variations in forms are called alleles. The ultimate combination of the chromosome pair is what makes the variation possible - combining the different variations of different characteristics to create a unique variation.
Genetic engineering is the process of altering/changing the genetic sequence of the DNA of an individual so as to alter the characteristic/trait expressed. Genetic engineering is a controversial topic though there has been many benefits achieved in the medical and agricultural sciences. For example, genetic engineering can be used to develop plants that can grow well in dry areas, or under certain disease pressure. Probably the most significant example of genetic engineering is in the production of insulin. The gene that produces insulin in humans is removed and placed in the genome of a bacteria. Then the bacteria will divide and all the offspring will have the insulin producing gene. This way, large amounts of insulin are produced by many genetically engineered E. coli bacteria.
When we observe and compare the individuals of the same variety or sub-variety such as genus or species, of plants and animals, we notice that they generally differ more between varieties that they do with individuals of the same variety. These differences seem to develop and increase over time. Parents will show more resemblane with their children than with their grandchildren. These differences we observe in a population are called variations.
The concept of variation was introduced by Charles Darwin in 1859 in his popular (and controversial) book titled 'On The Origin Of Species. In 1831, Charles Darwin boarded the H.M.S Beagle for a journey around the world and in 1835 th ship reached the Galapagos Island in South America. It was at this island that Charles made his important observations of different species of Finches. He observed that while the 13 species of finches were the same in size and shape, their beaks looked different in size and shape. But even with these differences in sizes of their beaks, Charles Darwin thought the finches had come from a common ancestor. It seemed as if each species of finch was well suited to its specific environment. The different shapes and sizes of their beaks enabled them to feed on different seeds and insects. Each beak type was a variation among members of the same species that enabled that species to survive better and reproduce in their specific environment.
The small changes observed are caused by small changes in the DNA called mutations. Such changes can occur dur to erros during mitosis or meiosis.
Variations result in adaptations, and therefore to survival. If birds are living in an environment where seeds are the main source of food, virds that have beaks that can crush seeds will be better adapted to that environment and will survive better than birds that cannot crush seeds. This concept translates across all other species including plants. Plants that have the ability to store water, such as cactuses, will sirvive in dry conditions while plants that cannot store sufficient amounts of water will wilt and die. And vice versa, only specific plants are adapted to live in marshy waterlogged environments. The same can be said for animals, only some animals can live in water, whether it is because they have gills, or they have to rise up to the water surface every so often to take large breaths of air into their lungs and then sink back into the water. Animals in the savanna survive better if they are able to catch prey, or if they are able to avoid being caught by predators.
Animals that survive better are able to reproduce more than those that do not survive better. So the better adapted animals produce more offspring than the less adapted animals. Over time, the population will have more individuals that are adapted than those that arent. And in some extreme cases, the less adapted individuals will be completely replaced by the adapted individuals. Charles Darwin described and named this concept Natural Selection. Natural Selection occurs when organisms that are best suited to their environments survive and reproduce successfully. This concept can also be called Survival for the fittest.
Because only the fittest individuals survive, organisms have to produce more offspring or reproductive cells (gametes) than those that are necessary to grow and to also reproduce. Plants produce a lot more pollen and only a few of them will be involved in the formation of seeds. But even then, plants produce a lot more seeds than those that will grow into new plants.
The process of intervention to produce more desirable organisms has been going on for some time. This process takes a long time to see results - usually many generations. Farmers, dog and horse breeders, along with scientists can now speed up the artificial selection process by using 'low-tech' or 'high-tech' technologies, such as;
1. Cloning
2. Artificial Insemination
3. In-Vitro Fertilization
4. Genetic Engineering
A clone is an individual that receives all of its DNA from one parent and is genetically identical to the parent. One of the most popular example of cloning is Dolly. In 1996, Ian Wilmut took a body cell from an adult female sheep and transferred the cell into an egg whose nuclues. The egg begun to divide behaving as if it had been fertilized. The dividing egg was then placed into a sheep (implanted) where it developed into a lamb. The DNA of the lamb that was born was identical to the DNA of the adult sheep from which the body cell was obtained.
Ecosystems can support only so many living things. There are limited amounts of food, water, sunlight, shelter and other resources. As a result, organisms struggle against one another to obtain what they need to survive. The struggle for these resources is called competition. For example, a fox will compete with other foxes to catch rabbits. Competition can also occur across different kinds of animals. For example, foxes also compete with hawks for rabbits. The rabbits compete with other herbivores for the food.
Some ecosystem changes are permanent. Organisms must respond to changes in order to survive. Organisms that cannot respond to ecosystem changes begin to die. When the last member of a species dies, the species becomes an extinct species. Some extinct organisms include all species of dinosaurs, mammoths, the saber-toothed cat, and many others.
The Tasmanian wolf, for example, became extinct about 65 years ago as a result of human actions. These wolves once lived in Australia. Farmers saw the Tasmanian wolf as a threat to their livestock and hunted the animal to extinction.
Pollution, global warming, habitat destruction, and hunting can also threaten the survival of organisms.
Below are examples of extinct animals, the first is the Tasmanian wolf and the second is the Saber toothed cat.
When a species is in danger of becoming extinct, it is called an endangered species. The flying squirrel is an example of an endangered species. Usually, only a few hundred individuals of the species exist.
Species with low numbers that could become endangered are called threatened species. The gray wolf, the manatee, and many others are threatened species.
Zoos were not originally started to preserve diversity. They were exotic collections for private collectors. They didn’t become public until the early 1800’s – in London. Today there are thousands around the world. Besides being home to a diverse group of animals and plants, Zoos can be educational institutions for students at all levels. Some zoos are part of a worldwide network that is attempting to protect and preserve endangered species. Animal exchange programs help to increase the genetic diversity essential to species survival. Support for research is also a large part of their program. Zoos are visible evidence of our attempt to preserve and maintain biological diversity.
Matter is anything that has mass and volume (occupies space).
The amount of matter in an object is called Mass. Mass can be measured in milligrams (mg), grams (g) or kilograms (kg). An object's mass remains the same.
Weight is a measure of the pull of gravity on an object. Therefore the weight of an object changes depending on the gravity. You would weigh less on the moon than you would weigh on Earth because the moon has less gravitational pull.
Matter can be found in three common states namely: solids, liquids and gases.
Solids: Solids have a shape and take up a definite amount of space. In solids, the particles of matter are packed tightly and mostly in a regular pattern. The pencil, pen, book, desk, blocks, wood, ice ... are all solids.
Liquids: Liquids do not have a definite shape, they take the shape of the container. Juice is a liquid, if you pour it into a glass, it will spread out and take up the shape of the glass. In liquids, the particles that make up matter are farther apart and can move more freely than in solids. Water, juice, milk, and oil are examples of liquids.
Gases: If you pour juice into a glass, it goes to the bottom of the glass makes the glass half full. Gases do not have a definite shape. In addition, if you put a gas into a container, it spreads out throughout the container. In gases, the particles spread out so as to fill the space in the container. If the space is small, the particles will be tight together, if the space is big, the particles will be spread out farther apart. Air is mostly made out of gases.
The most common form of matter in our universe exists in a fluid state called plasma, which is a gaslike mixture of positively and negatively charged particles. It is often considered to be the fourth state of matter.
All substances are either pure or mixtures. Pure substances can either be elements or compounds. Pure substances have unique set of properties, or characteristics that remain consistent. Mixtures can either be homogenous or heterogenous based on the interactions between the elements in the mixture.
Element
An element is a pure substance with its own set of physical and chemical properties that cannot be broken down into simpler chemical substances. It has only one type of atom present.
Compound
A compund is a pure substance that can be broken down by a chemical change into two or more elements. Compounds have more than one type of elements that are chemically combined.
Mixtures are two or more substances that are NOT chemically combined. They do not have constant characteristics such as boiling or melting points. The components retain their characteristic properties. They may be separated into pure substances by physical methods. Mixtures of different compositions may have widely different properties.
Homogenous Mixtures
These are mixtures which look as though they have only one set of properties. The blended mixture has equal amounts of both substances (all parts of the mixture are the same). If the homogenous mixture does not have any settling of any of the substances it is made of, then it is called a solution. Solutions occur because each particle interacts with other particles and the resultant particles are evenly distributed throughout the entire mixture.
In solutions, the substance in the smallest amount and the one that dissolves or disperses is called the SOLUTE. The substance in the larger amount is called the SOLVENT. water is commonly called the universal solvent. The gases, liquids, or solids dissolved in water are the solutes.
Heterogenous Mixtures
In a heterogenous mixture, the properties of the pure substances, can still be observed. If you notice there are two or more materials that are visible within a mixture, then it is a heterogeneous mixture.
Other Types of Mixtures
A suspension is a mixture made of parts that separate upon standing. To make a suspension, add fine sand to a bottle of water. Shake it, and watch the particles move. Soon, the sand particles will separate from the water and settle to the bottom of the bottle. You can separate a suspensio by filtration.
An emulsion is a suspension of two liquids that usually do not mix together. Emulsions are stable homogeneous mixtures of very small droplets suspended, rather than dissolved, in a liquid.
A colloid is a stable homogeneous mixture in which very small, fine particles of one material are scattered throughout another material, blocking the passage of light without settling out. Fog is a liquid-in-gas colloid. Smoke is a solid-in-gas colloid. Nonfat milk is a solid-in-liquid colloid.
Matter can change from one form to another, or create new materials Every kind of matter has its own distinguishing characteristic properties that can be used to identify the kind of matter it is. Properties are characteristics that can be used to describe how a substance behaves substance. These properties can be physical or chemical. Changes that matter can undergo fall into two classification categories: physical change and chemical change. A physical change occurs when a material changes form but not composition. A change of state is an example of a physical change where energy is used or released.
Changes of State: A change of state occurs when the particles of a substance gain or lose energy. Because this change is due to kinetic energy, the change of state is a physical process, which is reversible, and no matter how much kinetic energy is put into or taken away from the material, the material will always stay the same and its mass will also remain the same.
A chemical change occurs when two or more substances react and create one or more new substances. It is often permanent, although not always. Combustion is an example.
Any property that can be observed without forming a new substance is a physical property. These can include: color, texture, luster, smell, state, melting point, boiling point, hardness, malleability, ductility, crystal shape, viscosity, solubility, density and conductivity (electrical and heat). Any property that describes how a substance reacts with another substance when forming a new substance is a chemical property. Chemical properties include: reaction with acids, ability to burn (combustibility), reaction with water, behaviour in air and reaction to heat, toxicity, stability.
How do you know a chemical change has occured?
There are some tell tale signs that you can use to detect if a chemical reaction has occured. For instance:
Another term for a chemical change is chemical reaction. Chemical reactions have two parts. A substance present before a chemical change is a reactant. A substance produced by a chemical change is a product. A chemical equation uses letters and numbers to represent the amounts of reactants and products involved in a chemical change. An arrow separates the reactants on the left from the products on the right.
An element is a pure substance made up of only one type of particle, or atom. Each element has its own unique set of distinguishing properties and cannot be broken down into simpler substances by means of a chemical change.
A compound is a pure substance made up of 2 or more elements chemically combined together. Compounds can be broken down into the elements that they are composed of.
An atom is a particle that consists of a nucleus, which contains protons and neutrons, surrounded by a cloud of electrons. The atom is the basic particle of the chemical elements. Different elements can be distinguished from each other by the number of protons that are in their atoms.
Atoms are extremely small. A human hair is about a million carbon atoms wide.
More than 99.9% of an atom's mass is in the nucleus. Each proton has a positive electric charge, while each electron has a negative charge, and the neutrons, if present, have no electric charge. If the numbers of protons and electrons are equal, as they normally are, then the atom is electrically neutral. If an atom has more electrons than protons, then it has an overall negative charge, and is called a negative ion (or anion). On the contrary, if an atom has more protons than electrons, it has a positive charge, and is called a positive ion (or cation).
1. Dalton's Model
John Dalton
This model is also described as the billiard balls model. In 1803, John Dalton conducted experiments with gases and used the results to propose the modern theory of the atom based on the following assumptions.
2. Thomson's model
Sir Joseph John Thomson
This model is also described as the plum pudding model. The positive charges fills the atom while the electrons were embedded throughout the atom. Thomson discovered the electron and since the electron was negative, but atoms neutral, there had to be positive charge inside atoms. Thomson used a beam of cathode rays in a CRT with both an electric field and a magnetic field perpendicular acting on the beam. With only the electric field on, the beam was deflected toward the positive plate. With only the magnetic field on, the cathode rays were deflected into a curved path. When both fields were on, and the field strengths equal, the cathode rays were not deflected.
3. Rutherford's Model
Ernest Rutherford
Around 1911 Rutherford, Marsden and Geiger performed experiments to test the Thomson model. They directed alpha particles from radioactive sources onto thin gold foils. The Thomson model predicted that most of the alpha particles would go straight through, and only a few would be deflected at small angles since the electrons in the atom have much less mass than alpha particles. Most of the particles went straight through undeflected, some were deflected at angles of more than 10o and a few were deflected almost straight back. He concluded that most of the atom was empty space with most of the mass and all of the positive charge concentrated in a very small region (the nucleus). Scattering angles indicated the size of the nucleus was about 1015 to 1014m in radius.
In Rutherford's model, electrons could 'orbit' the nucleus at any energy level. The closer the alpha particle is to the nucleus the greater its potential energy.
An element is identified by the number of protons contained in the nucleus of each of its atoms. Every element has a unique number of protons and is defined as the element's atomic number.
Mass Number - The atomic mass number of an element is simply the sum of the protons and neutrons in the nucleus of 1 atom of the element.
Atoms of the same element may have different numbers of neutrons, which means they will have different mass number. Atoms of the same element that have different atomic masses are called isotopes. If you look at a detailed periodic table, you will notice that an isotope’s atomic mass is listed beside its name or symbol.
The atomic mass is the average mass of an element in atomic mass units (amu.) The mass in an atom is roughly the mass of one proton or neutron. The atomic mass is a decimal number on the Periodic Table because it's an average of the various isotopes (one or more atoms that have the same atomic number but different mass numbers) of an element.
One way of classifying elements is to sort them into categories, based on their distinct properties. Long before anyone knew any detail about the atoms or any of the periodic properties the elements were divided into two broad categories → metals and non-metals.
Scientists classify metals into 3 categories: Alkali metals, Alkaline metals and transition metals.
Alkali metals are Group 1 elements located on the far left of the periodic table along with Hydrogen which is not a metal. Alkali metalks include Sodium (Na), Lithium (Li) and Potassium (K). They are soft and extremely reactive, therefore they easily form compounds with other substances. They never exist by themselves in nature.
Alkaline metals are located to the right of alkali metals. These are not as reactive as the alkali metals, but they are also soft and light. They include Calcium (Ca), Magnesium (Mg) etc. They are essential to many living things.
Transition metals are a large group of elements in the center of the periodic table. They include copper, iron, gold, nickel, and zinc. Most transition metals are hard and shiny. They react slowly with other substances. Transition metals are used to make coins, jewelry, machinery, and many other items.
On the right side of the periodic table are metalloids and nonmetals.
Metalloids include silicon, boron, and arsenic. They share properties with both metals and nonmetals. They are semiconductors, i.e., at high temperatures they conduct electricity, like metals, but at very low temperatures they stop electricity from flowing, like nonmetals. Because of this, silicon and other metalloids are used in machinery, computer chips, and circuits. Nonmetals, such as oxygen, carbon, and nitrogen, have properties opposite to those of metals. At room temperature, most of them exist as gases or as brittle solids. Nonmetals cannot be rolled into wires or pounded into thin sheets. Most nonmetals are poor conductors of heat and electricity.
Noble gases, in the far-right column in Group 18 of the periodic table, are nonmetals that do not react naturally with other elements. These gases have many uses. Argon is used in electric light bulbs. Neon, when exposed to electricity, produces the bright colors of some signs. Xenon is used in car headlights. Helium is often used in balloons.
To the left of the noble gases are elements called halogens. These include fluorine and chlorine. They are very reactive nonmetals. Chlorine combines with sodium to form sodium chloride (table salt).
Rare Earth Elements - There are 30 rare earth elements. Many of them are synthetic or manmade. They're found in group three of the periodic table and the sixth and seventh groups.
A compound is a formed when two or more elements combine together in a chemical reaction. Compounds can be classified as acids, bases or neutral compounds. Acids turn blue litmus paper red, bases turn red litmus paper blue, and neutral compounds cause no effect on litmus papers. Compounds can also be classified depending on the type of bond joining the component elements, such as ionic bond (Ionic compounds) or covalent bond (Molecular compounds). Ionic compounds are created by the reaction between a metal and a non-metal. Ionic compounds are solids in nature and soluble in water. They conduct electricity in aqueous solution. Ionic hydrates are ionic compounds that contain loosely bonded water molecules. Hydrated compounds appear different from unhydrated compounds. For example, hydrated copper II sulfate forms blue crystals, while the unhydrated form is a white powder. Molecular compounds are created by the reaction between a non-metal and a non-metal. Molecular compounds are either solid, liquid or gases, depending on the component elements. Their solubility also varies, and they do not conduct electricity in aqueous solutions. A molecule is a group of nonmetal atoms held together by covalent bonds. The molecular formula indicates the number of atoms of each type.
Understanding Formulas for Compounds
Compounds have a chemical name and a chemical formula. The chemical formula uses symbols and numerals to identify which elements and how many atoms of each element are present in the compound. For example:
Ethanol ( C2 H6 O ) has 2 carbon atoms, 6 hydrogen atoms and 1 oxygen atom. To determine a chemical name, a standardized chemical naming system, or nomenclature, is used. The IUPAC ( International Union of Pure and Applied Chemistry ) is responsible for determining the appropriate name for each compound.
How Are Molecular Compounds Named?
A compound made from two elements is called a binary compound. Rules for naming binary molecular compounds:
Examples: CO2(g) carbon dioxide, CCl4(l) carbon tetrachloride, SiO2(s) Silicon dioxide.
How Are Ionic Compounds Named?
Two rules:
One exception – Where negative ions are polyatomic ions, the name remains unchanged.
All ionic compounds have distinct (different) crystal shapes.
A chemical reaction is said to have occurred when one of the following observations are made. These observations can be classified into physical, chemical or nuclear changes.
Physical changes
State or energy change: This involves the change from solid to liquid or to gaseous state. The energy change is usually small. There is no new substance formed.
Chemical changes
This may include color change, change in odor, physical state and energy change. A new substance is formed, and the changes may be irreversible. Chemical changes are associated with moderate energy changes, higher than physical changes.
Nuclear changes
Nuclear changes often result in emission of radiation energy. New elements are formed, and the energy change is usually much larger than chemical changes.
The evidence of a chemical reaction can be explained using the major aspects that change when a chemical reaction occurs. These include:
Reactions can be classified into five different types as follows:
Chemical reactions can be written as word equations which gives the names of all the reactants (separated by a "plus' sign + ) followed by an arrow which points to the names of all the products.
Iron + Oxygen + Water → Rust
Iron plus oxygen plus water produces rust
Iron, oxygen and water are the reactants. Rust is the product.
Breaking Chemical Bonds
Chemical bonds are forces that cause a group of atoms to behave as a unit. Energy is stored in these bonds. To break the bonds energy must be added. When bonds form, energy is released. All chemical reactions involve energy being absorbed ENDOTHERMIC, or released EXOTHERMIC. Photosynthesis is an endothermic reaction, because it needs light energy to occur, whereas combustion is an exothermic reaction, because it gives off light and heat.
The speed of a chemical reaction is called the reaction rate.
Catalysts speed up reactions
A catalyst is a substance that help a reaction proceed faster and are not consumed in the reaction.
Several types of reactions involving catalysts can be found in living and non-living things. Enzymes are natural catalysts that help in the reactions in the body, which break down food. They also get rid of poison in the body. Catalase (an enzyme found in plant and animal cells) speeds up the breaking down of hydrogen peroxide into harmless oxygen and water.
Inhibitors slow down chemical reactions
Inhibitors are substances that slow down chemical reactions. Plants have natural inhibitors in their seeds to prevent germination until the right conditions are present. Inhibitors are added to foods to slow down their decomposition.
Combustion
Combustion is the highly exothermic combination of a substance with oxygen. Combustion requires heat, oxygen, and fuel. The products of combustion include carbon dioxide and moisture.
Burning fossil fuels (such as propane) produces carbon monoxide, carbon dioxide, sulfur oxides, nitrogen oxides, smoke, soot, ash and heat. Some of these products are pollutants.
Corrosion
Corrosion is a slow chemical change that occurs when oxygen in the air reacts with a metal. Corrosion is a chemical reaction in which the metal is decomposed (eaten away), when it reacts with other substances in the environment. The corrosion of iron is called 'rusting'.
Preventing Corrosion
Involves protecting metal from contact with the environment and the factors that affect the reaction rate of this chemical reaction.
Our body needs about 25 different chemicals for normal growth. The complex organization of these chemicals produces organic compounds which contain Carbon, as well as mostly Oxygen and Hydrogen. Substances that do not contain Carbon are called inorganic compounds. The organic nutrients, which come primarily from green plants, are classified into four major groups.
| Organic Compounds | Function / Role in nutrition | Dietary Sources |
|---|---|---|
| Carbohydrates | They are organic molecules consisting of carbon, hydrogen, and oxygen. They are a source of energy for metabolism | sugar, starch, cellulose, glucose. food sources such as rice, grains, potatoes, fruits |
| Lipids | They are compounds composed of many carbon, hydrogen, and oxygen atoms. They function as storage of unused chemical energy. They act as a source of energy especially when carbohydrates are depleted. | Vegetable oils, nut oils, some dairy products |
| Proteins | They are organic compounds made up of amino acids. Each protein has its own unique number, combination and arrangement of amino acids. They have several functions in the body including growth and repair, as well as a source of energy. | Fit closely together to form a continuous protective layer |
| Nucleic Acids | These are large complicated molecules that play a major role in heredity and in controlling the cell's activities. Examples include DNA and RNA. | They make up the genetic material that plays a role in heredity. They are also building units for genes that then get translated into proteins. All proteins in the body are derived from DNA through a process called translation. |
Plants require carbon, oxygen and hydrogen from the air, and nitrogen, phosphorus, potassium, magnesium, calcium and sulfur from the soil. Plants require these nine elements in large quantities for them to gorw so they are called macronutrients. There are other elements that are also needed, but not in large quantities. These elements are called trace elements or micronutrients.
Green plants require 18 elements for proper growth and functioning, while humans need 25 elements, which are used by for growth and function. The process of taking in the nutrients (elements and compounds) we need is called ingestion.
Some of the macronutrient elements are required to synthesize enzymes and vitamins. Enzymes are special protein molecules that regulate chemical reactions in living organisms. Vitamins are large organic molecules with several functions including helping enzymes function properly. The body cannot synthesize the elements so they must be provided in food.
Most elements are found in food as large complex compounds that require to be broken down first into smaller units. The digestive system is mostly esponsible for this break-down of large food molecules into smaller units through a process called hydrolysis. For example 1 molecule of maltose is broken down, in the presence of water and a specific enzyme, into 2 molecules of glucose. The products of digestion, such as glucose and amino acids, are then absorbed through cell membranes and into the bloodstream, which carries them to where they will be used or stored.
Below is a list of macronutrients and their importance in plants and humans:
| Nutrient | Function /Importance in Plants | Importance in Humans |
|---|---|---|
| Nitrogen | Proteins & chlorophyll. Leaf and stem growth | Composition of proteins & nucleic acids, growth and repair of tissue |
| Phosphorus | Root and flower growth, cellular respiration & photosynthesis | Composition of bones, teeth & DNA. Important in several metabolic reactions |
| Potassium | Stimulates early growth, starch and protein production, disease resistance, - chlorophyll production & tuber formation | Muscle contraction & nerve impulses |
| Magnesium | Chlorophyll structure, photosynthesis | Composition of bones & teeth, enhance the absorption of calcium & potassium |
| Calcium | Cell wall structure, cell division | Composition of bones & teeth, blood clotting, muscle & nerve function |
| Sulfur | Production of fruits and grains | Protein synthesis, enzyme activation and detoxification |
| Sodium | Controls osmotic pressure in plant cells and results in a more efficient use of water | Helps regulate nerve impulses in nerves and muscles |
Below is a list of micronutrients and their functions:
| Nutrient | Function /Importance |
|---|---|
| Chlorine | Helps regulate water balance, plays a role in cell membrane function, part of the hydrochloric acid in stomach that helps digest foods |
| Iron | Crucial part of red blood cells, regulating oxygen transport |
| Zinc | Essential component in enzymes which regulate formation of proteins and carbohydrate metabolism |
| Iodine | Major component in thyroid hormones which regulate metabolism |
| Selenium | Component of antioxidant enzyme that helps decay of cell function |
| Copper | Promotes iron absorption and utilization, component of many enzymes and helps regulate nerve activity |
| Manganese | Component of some enzymes involved in bole formation and protein metabolism |
| Fluorine | Helps regulate calcium deposition |
| Chromium | Activates vitamin B3 to control use of blood sugar in energy production |
| Molybdenum | Key component of 3 enzymes that regulate metabolism |
| Cobalt | Component of vitamin B12, which helps regulate red blood cells |
The optimum amount of a substance is the amount of that substance that provides an organism with the best health. A micronutrient may be present in larger amounts than normal. If this occurs it can have harmful effects. Not enough of an element can also have harmful effects.
Plants take in inorganic compounds to make organic compounds. Consumers use the organic compounds made by plants for their energy, growth and repair. When organisms take in these compounds, other substances are also taken. These substances may or may not be harmful.
Some nutrients enter the roots by diffusion. This action continues until the areas are equal concentrations.
Water moves through plants by osmosis. In this process, water moves through the walls of the plant's roots from an area where there are more water molecules to an area where there are fewer water molecules.
Plants need some nutrients at high concentrations in their roots. These nutrients may have higher concentrations in the roots than in the surrounding soil. To maintain these high concentrations, (against diffusion gradient), plants move more nutrients into their roots from areas of lower concentration (in the soil) by a process called active transfer. This process requires energy.
Some organisms get the nutrients they need by restricting other organisms from accessing the same nutrients.
Plants obtain nutrients from the soil and over time can deplete the nutrients available in the soil. Fertilizers are substances that can be applied to the soil to replenish the lost nutrients. The three numbers on a bag of fertilizer refer to the percentage of nitrogen, phosphate and potassium that is available to plants from that bag of fertilizer. For example, a bag labeled 5-10-5 indicates it has 5 % nitrogen, 10 % phosphate and 5 % potassium. The remaining 80% contains some micronutrients and some fillers necessary for the effectiveness of the fertilizer.
Until the early 1900s, plants received their nitrates exclusively from nature. The artificial production of fertilizers increased the nitrogen levels available to plants in the soil. Crop production has doubled worldwide due to the use of artificial fertilizers and high-yield varieties. Nitrogen is used by plants for increased plant growth. Crop and livestock production requires a lot of water and fertilizers, which also increases the costs of production. The planting of only one crop (monoculture) means the same nutrients are continually depleted from the soil. Monoculture also increases the chance of disease spreading through the entire crop. Chemical agents used to protect the crop (pesticides and herbicides) reduce the amount of damage, but they are costly and have harmful effects on the environment.
Pesticide, herbicide and fungicide use is now common agricultural practice worldwide. Herbicides control weeds, insecticides control insects and fungicides control fungal diseases in crops. The increased prevalence of these challenges might be related the current commercial agriculture practices such as monocropping.
The invention of DDT by Swiss chemist Paul Müller was originally seen as a breakthrough in medicine. Typhus a disease transmitted by lice was rampant during the World War II and was the disease that wiped out Napoleon’s army in the 1800s. DDT wiped it out. It proved to be so effective that Müller was awarded the Nobel Prize in Medicine for his discovery. During the 1950s it was used to try to control an outbreak of malaria. DDT undergoes bioaccumulation within the food chain and can cause devastating effects. The use of DDT was recognized as having potentially harmful effects. Banning its use would also negate the positive effects it was having in controlling malaria (In Zanzibar alone – the incidence of malaria dropped from 70% to 5% over a 6 year span). When a restriction on the use of DDT was implemented in 1984, the incidence of malaria returned to the 50-60 % level. Nothing else proved to be as effective in controlling the insects that carried malaria.
Research into newer and safer pesticides has resulted in the development of pesticides that can break down faster in the environment after they have been applied. It is now widely recognized that natural processes and cycles can minimize the effects of these pesticides, but it still remains a hotly debated topic.
Sulfur, nitrogen and carbon oxides emitted from industries (such as smelters) combine with water vapor in the air to produce sulfuric, nitric and carbonic acid. These pollutants then fall to the ground as acid precipitation. Acid rains can have several effects including:
To neutralize acid rain precipitation and reduced soil pH from fertilizers, lime (calcium hydroxide) can be added to agricultural soils and lakes.
In 1996 an agreement between Canada and the US targeted a 10% reduction in industrial exhaust emissions by the year 2000. Vehicle emissions for cars built before 1998 was also targeted to be reduced by 60%. As a result total emissions are on the decline. Catalytic converters contain a ceramic or wire honeycomb-like structure that is coated with a thin layer of metallic catalysts, which speed up chemical reactions, without being used up. A converter helps the formation of CO2 and H2O, reducing CO and NO2. The purpose of the converter is to encourage complete oxidation.
Every chemical has the potential to be harmful, even the ones we take to help us. It is the dose, our susceptibility and how it reacts with other chemicals that determine it toxicity. Tough decisions need to be made to determine if it is more beneficial than harmful. Evaluation of the risks and benefits of any chemical, form the basis of how chemical use is regulated.
As the world population grows, waste production also increases and the proper handling of this waste should always be addressed.
Environmental Monitoring
Persistent pollutants accumulate and take a long time to degrade. It is the concentration of these wastes that can affect living organisms. To determine the concentration scientists test wastes, persistent and non-persistent to determine how to handle them and deal with their effects in the environment. Monitoring keeps track of something for a specific purpose. Clarity may be one indicator, but clear water does not indicate what chemicals are present. Water Quality is determined using chemical and biological indicators according to what the water is going to be used for.
Most types of pollution adversely affect water quality and directly affect living organisms. Microscopic organisms (bacteria) can cause serious health problems if they are present in sufficient numbers. Samples are taken to identify their presence to avoid contamination of the water supply. Chemical indicators of water quality include: dissolved oxygen, acidity, heavy metals, nitrogen, phosphorus, pesticides, salts – such as sodium chloride and magnesium sulfate.
Pollutants entering the environment from specific locations are point source pollutants. These are easy to monitor and control. Non-point source pollutants are those that enter the environment from locations that cannot be easily monitored or controlled. They occur as a result of run-off or leaching and they get dispersed quickly. The 4Rs – Reduce, Reuse, Recycle and Recover can be used to develop a basic framework to reduce the amount of waste pollutants that are produced. Some of this waste can be reduced, recycled, recovered or reused, but most of it is placed in landfill sites. The most preferred option is to reduce – in other words don’t make as much waste and the problem of disposal will take care of itself.
Biodegradation occurs in the environment because living things (earthworms, bacteria and fungi) are actively breaking down organic substances, including many pollutants. Microorganisms are especially important in the biodegradation of pollutants. The existing organic molecules provide carbon atoms, which are used to build biological compounds, such as carbohydrates and proteins. During the winter, biodegradation is slow, because temperature is one factor that affects the rate of biodegradation. Other factors include soil moisture, pH, oxygen supply and nutrient availability.
Bioremediation:
Bioreactors are a new technology that speeds up the rate of biodegradation by adding water to organic waste in a sanitary landfill site. Planting vegetation also encourages faster biodegradation because the populations of bacteria and fungi are larger around plant roots and this higher level means more microbial activity. Phytoremediation is a technique that can be used to reduce the concentration of harmful chemicals in the soil or groundwater. Plants have been used to clean up metals, hydrocarbons, solvents, pesticides, radioactive materials, explosives, and landfill leachates. The plants are able to absorb and accumulate large amounts of these chemicals. When the plants have matured, they are harvested, burned or composted. Photolysis is the breakdown of compounds by sunlight. The formation of ozone is an example of this process. Another example of photolysis is photodegradable plastic. Photodegradable plastic is made of chemicals that react when exposed to sunlight. In three months, the plastic becomes a fine powder that is easier to dispose of.
Solid waste includes the garbage collected from households, industries, commercial retailers, institutions and construction or demolition sites.
Remember, all matter is made up of atoms, and all atoms are made up of protons, neutrons and electrons. The protons are the positively charged particles and the electrons are the negatively charged particles. When the positive and negative particles are equal, the charge equals out. When there are more electrons than protons, you have a charged atom, called an ion.
Electrons spin around the outside of the nucleus and are held in that place by the force of attraction from the protons in the nucleus. However, electrons can be lost by one atom and picked up by another atom resulting in a change in the charge of both atoms. The atom that has lost the electron now becomes positively changred (because it has more protons than electrons) and the atom that gains an electron becomes negatively charged, because it now has more electrons than protons. The transfer of charged particles from one atom to the other can build a series of electrically charged atoms. Electricity refers to the movement and transfer of the energy of charged particles. This energy is used to power motors, lights, appliances, and many other devices.
When two materials touch one another, electrons can move from one material to the other. This causes one maerial to become more negatively charged and the other positively charged. This transfer of electrons causes an imbalance which results in static electricity. Objects with the same electric charge repel each other and objects with opposite charge attract each other. Some materials lose electrons more easily than others while others attract electrons more easily. For example, the atoms on the human skin more readily lose electrons, becoming positively charged. The atoms on a cat's fur do not lose electrons easily, so if you pet a cat you can create static electricity.
Benjamin Franklin was the first to describe the charges as 'positive' or 'negative'. When a charged object is placed near a neutral object, the charged object can affect the overall charge of the neutral object. Like charges within the neutral object are repelled, and unlike charges are pulled toward it. This movement can result in an induced charge. An induced charge is a static charge caused by the presence of an object that itself has a net positive or negative charge. When you rub a balloon on your hair, some electrons leave your hair and are transferred to the balloon. The balloon then has a net negative charge. When you place that balloon near a wall with no net charge, the negative particles in that area of the wall are repelled. This leaves a net positive charge on the surface of the wall. The balloon and wall then attract each other, and the balloon sticks to the wall. Evidence indicates that lightning can also be produced as a result of induced charges. Storm clouds can accumulate a negative charge near the bottom of the cloud. This can induce a positive charge in the ground below the cloud. This imbalance of charges can result in the discharge called lightning, which can reach 5 km in length.
A conductor is a material through which an electric charge flows easily. Most conductors are made of atoms from which some electrons are likely to become unattached. Metals such as copper are the best conductors. This is why copper is commonly used in electric wiring.
Semiconductors are almost perfect conductors - they have almost no resistance to electron flow. Silicon semiconductors are used extensively to make computer microchips. The largest obstacle is to get the semiconductor to work at reasonable temperatures for practical applications. Superconductors are materials that offer little, if any, resistance to the flow of electrons.
An insulator is a material that does not allow an electric charge to transfer easily. Conductors and insulators of electric charge are very similar to conductors and insulators of heat energy.
Electrical Discharge is the movement of charges whenever an imbalance of charges occurs. The action results in neutralizing the objects. The over-charged electrons repel the electrons in the object and the positive protons attract the charged electrons causing a discharge or 'miniature lightning bolt'. There is now an electron balance. An ionizer can be used to neutralize charges on non-conductors.
If a bare wire touched the metal case of an appliance, it could become electrified and can harm people when they touch the appliance. To avoid this problem, a grounding wire is connected to the metal case of the appliance. The grounding wire connects the case to the ground and because this charge gets distributed over much of Earth, the charge on the case is then too small to cause problems.
Electric charges flow through conductors along different paths. Each path for electric charge is an example of a circuit. In circuits, electric charges move within wires, bulbs and other devices.
All circuit diagrams have four basic parts:
A simple circuit consists of an energy source such as a battery, a device such as a lamp, and connecting wires. The flow of an electric charge through a circuit is called current electricity. In a circuit, energy from a source such as a battery causes an electric charge to flow through the wire. Electrons that are not strongly attached to the atoms inside the wire move, causing current electricity.
Batteries stop working when the chemical reactions inside them can no longer transfer energy to electrons and move them through the wire in this manner.
Although the movement of negatively charged electrons is most often referred to when studying current electricity in wires, current is always said to flow from the positive to the negative terminal in a circuit. This is called conventional current. This way of describing the movement of electric current originated before scientists fully understood electricity. However, it is still the way used to describe how circuits operate.
A switch can control the flow of a charge in a circuit. When the switch is opened, the flow is halted. The circuit is incomplete and is then called an open circuit. When the switch is closed, the electric charge resumes its motion. When current flows once again, the circuit is called a closed circuit.
Direct current, or DC, refers to current that flows in one direction. Batteries provide DC, as do solar-powered cells. The very first commercial electric power stations also used DC.
Alternating current, or AC, refers to the electric charge that does not flow through the circuit in one direction. AC power is transmitted when the charge changes direction, moving back and forth at regular intervals. The main advantage of AC is that this type of current can be transported over long distances with far greater efficiency.
Resistors lower the amount of electric charge that flows through a device. Lights and other devices connected in a circuit act as resistors, because they too reduce current flow. A light bulb converts electrical energy to both heat and light.
The steady flow of charged particles is called electrical current. The flow continues until the energy source is used up, or disconnected. The rate at which an electrical current flows is measured in amperes (A). This flow varies from a fraction of an ampere to many thousands of amperes, depending on the device. An instrument used to measure very weak electric current is called a galvanometer. Larger currents are measured with an ammeter.
Electrical energy is the energy carried by charged particles. Voltage is a measure of how much electrical energy each charged particle carries. The higher the energy of each charged particle, the greater the potential energy. Also called 'potential difference', the energy delivered by a flow of charged particles is equal to the voltage times the number of particles. Voltage units are volts (V), and for safety purposes, the voltage of most everyday devices we commonly use is relatively low, while industries and transmission lines are relatively high. A simple way to measure voltage is with a voltmeter. [red to positive (+) and black to negative (-)] Some voltmeters can measure a wide range of voltages. These multi-meters should be used with caution, so that the sensitive needle is not damaged (by testing a low range with high voltage).
In a series circuit, there is only one path along which current electricity can flow. Each battery supplies more energy that causes electric charge to flow. The light bulbs receive the sum of the energy that comes from the two batteries. This energy is measured in volts (V). Because each battery has 1.5V, the two batteries together deliver a total of 3V. A higher voltage causes more electric charge to move through the light bulbs.
The total resistance is the sum of resistances of the individual devices such as bulbs. For example, two identical light bulbs together in a series circuit will have twice the resistance of either bulb by itself. The voltage of current electricity from a normal wall outlet is about 120V. Each small bulb on a strand of lights operates on about 2.5V. This means that the voltage from a wall socket is about 50 times the voltage that a single bulb requires. To provide the correct voltage to each bulb, each strand could only have 50 bulbs. If there were more, then each bulb would not receive enough voltage to light up.
In a parallel circuit, there are multiple paths along which current electricity can flow. For example, in a string of lights wired in a parallel circuit, when one bulb burns out, there are other paths along which electric charge can flow to all the other bulbs. Parallel circuits are used everywhere that we use electricity, including homes, stores, and offices. If any one device on the circuit burns out, the other devices on the circuit will keep working.
A short circuit is a path for current electricity that has little or no resistance. Current flowing in a short circuit can reach dangerously high levels and will also generate heat. A fuse is a device that prevents dangerous levels of current from continuing to flow through a circuit. A fuse contains a piece of metal that melts if it is heated. This melting breaks, or opens, the overloaded circuit.
House Wiring: Practical wiring in the home uses parallel circuits. The voltage across each load is the same, and by turning on one appliance in the circuit, the energy will not be reduced to the other devices. Caution – current through wires connected to the source increases whenever another branch in the circuit is closed.
Resistance is a measure of how difficult it is for the electrons to flow through a conductor. Resistance also converts electric energy into other forms of energy. Generally, it can be said that conductors have low resistance and insulators have high resistance. The standard unit for resistance is ohm (Ω). Resistance can be measured directly with an ohmmeter, but a multi-meter is used more often to measure resistance.
Calculating Resistance: Electrical resistance is calculated by finding the ratio of the voltage across the load (V) to the current through the load (I). This is called Ohm’s Law. R = V / I. The more resistance a substance has, the greater the energy gain it receives from the electrons that pass through it. The energy gain is evident in heat and light energy (light bulb filament, wire in a toaster).
Different resistors are used for different applications, especially in electronics. There are many styles, sizes and shapes. The major application for resistors is to control current or voltage to suit the specific needs of other electrical devices within the same circuit. The two most common resistors are the wire-wound and carbon-composition types. The colored strips on a resistor usually indicate the level of resistance and quality.
To change electron flow gradually, a variable resistor, or rheostat is used (a dimmer switch, volume control knob).
Power cables are composed of many thin copper stands, separated in groups by paper insulation, and covered by a rubber insulation material, which reduces resistance and heating in the cable, while still making it flexible enough to handle.
Energy transformation, also known as energy conversion, is the process of changing energy from one form to another. The four most common forms of energy are: chemical (potential or stored energy stored in chemicals), electrical - energy of charged particles, transferred when they travel from place to place, mechanical - energy possessed by an object because of its motion or its potential to move, and thermal - kinetic energy of a substance.
A thermocouple is a device that can convert thermal energy into electrical energy. It consists of two different metals (bimetal) joined together that conduct heat at slightly different rates. When heated, the difference in conduction results in electricity flowing from one metal to the other. The basic principle of the thermocouple was discovered by Thomas Johann Seebeck in 1821, and was named the Seebeck Effect. Thermocouples are useful for measuring temperatures in areas that are difficult to access or too hot for a regular liquid-filled thermometer.
Ovens and heaters do the opposite. They convert electrical energy into thermal energy. A thermo-electric generator is a device based on a thermocouple that converts heat directly into electricity without moving parts. Several thermocouples connected in a series are called a thermopile. Thermopiles are extremely reliable, low-maintenance devices and are often used in remote locations for emergency power generation.
The piezoelectric effect produces sound by converting electricity into motion (vibrations). When a piezoelectric crystal, such as quartz, or Rochelle salt is connected to a potential difference, the crystal expands or contracts slightly. Material touching the crystal experiences pressure, creating sound waves or vibrations.
Motion to Electricity: A barbeque spark lighter uses the piezoelectric effect in reverse. When a crystal or Rochelle salt is compressed or pulled, a potential difference is built up on the opposite sides of the crystal. Conductors then take this through a circuit to produce electric energy (a spark).
Electric actuators most commonly pair with motors to provide linear or rotary motion. Together they convert electricity into kinetic motion.
An incandescent resistance filament (load) glows white-hot when electricity is passed through it. In fluorescent tubes a gas glows brightly and when crystals are struck together they can produce light. LED’s (light-emitting diodes) are solid –state components that use a fraction of the power. When connected to a semiconductor chip in the right direction, they will produce light and last for many years.
Solar panels, containing photovoltaic cells can convert light into electrical energy. The photovoltaic (PV) cells, or solar cells, are made of semiconductor materials, such as silicon. When light is present, the material, breaking electrons loose – allowing them to flow freely, absorbs some. This current is drawn off by metal contacts on the top and bottom of the cell and then used in devices such as calculators, heater, or emergency telephones. Individual solar cells are combined in modules, to form arrays to produce larger amounts of electric current.
An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic cells or galvanic cells and those that generate chemical reactions, through electrolysis for example, are called electrolytic cells.
Two metal electrodes are surrounded by an electrolyte. These cells supply a steady current. The chemical reaction in a cell releases free electrons, which travel from the negative terminal of the cell, through the device, which uses the electricity, and back to the positive terminal of the cell. The chemical reactions within the cell determine the potential difference (voltage) that the cell can create. Several cells connected in series produces a higher voltage, and is commonly referred to as a battery, which is a sealed case with only two terminals.
A primary cell is one in which the reactions will not continue after the reactants are used up. Wet cells use a liquid electrolyte. Wet cells are 'wet', because the electrolyte is a liquid (usually an acid). Each electrode (zinc and copper) reacts differently in the electrolyte. The acidic electrolyte eats away the zinc electrode, leaving behind electrons that give it a negative charge. The copper electrode is positive, but it is not eaten away. Electrons travel from the negative terminal (attached to the zinc electrode) through the device and on to the positive terminal (attached to the copper electrode).
Dry cells referred to as 'batteries', are called dry cells, because the chemicals used in them are a paste. The dry cell is made up of two different metals, called electrodes in an electrolyte. An electrolyte is a paste or liquid that conducts electricity because it contains chemicals that form ions. An ion is an atom or group of atoms that has become electrically charged through the loss or gain of electrons from one atom to another. The electrolyte reacts with the electrodes, making one electrode positive and the other negative. These electrodes are connected to the terminals.
A secondary cell uses chemical reactions, which can be reversed. These are referred to as rechargeable batteries. Rechargeable cells use an external electrical source to rejuvenate the cell. The reversed flow of electrons restores the reactants in the cell. The most common reactions that are efficient enough to be used for these types of cells are Nickel Oxide and Cadmium (NiCad). The reactants are restored, but the electrodes will eventually wear out over time.
Fuel Cells: combine hydrogen and oxygen without combustion. Electricity, heat and pure water are the only by-products of the fuel cell’s reaction. They are 50-85% efficient.
| Type | Uses | Pros / Cons |
|---|---|---|
| Zinc-carbon | Flashlights, portable stereos, CD players, remote controls, toys etc. | Not efficient at low temperatures |
| Alkaline | Flashlights, portable stereos, CD players, remote controls, toys etc. | Last longer than zinc carbon, but more expensive |
| zinc-air | Calculators, hearing aids, watches and smaller remote controls, car keys. | Highest energy per unit mass, but discharge rapidly |
| Type | Uses | Pros / Cons |
|---|---|---|
| Nickel-cadmium | Electric shavers, laptops, power tools, portable TV’s | Rechargeable hundreds of times |
| Nickel-metal hydride | Cameras, laptops, cell phones, hand tools, toys | Less toxic than NiCad – 40% more energy density than NiCad, rechargeable, no memory effect, lose charge when stored |
| Type | Uses | Pros / Cons |
|---|---|---|
| Lead acid | Cars, motorbikes, snowmobiles, golf carts | Dependable, but heavy and has a corrosive liquid |
Magnetism
Magnetism is the ability of an object to push or pull another object that has magnetic property. Magnets also work with metals like iron and nickel.
A magnet has two poles, North (N) and South (S). Like poles repel, while unlike poles attract. Magnets always have a N and S pole, even if you break a magnet into two, it will form 2 magnets, each with a N pole and a S pole.
The Earth acts as a magnet with a North and South pole.
Atoms also act like magnets. In most non-magnetic materials, the N and S poles are random so they cancel each other. In materials where the N ans S poles of the atoms are aligned in the same direction, they form a permanent magnet. Iron, Nickel and Cobalt are attracted to magnets because their atoms can align to match those in the magnet thereby acting as weak magnets. When you place pieces of these metals over a magnet they form lines which correspond to the forces around a magnet called magnet field. The closer the lines are, the stronger the magnetic force in that area.
Electromagnets
An electromagnet is an electric circuit that produces a magnetic force. The moving electrons in the circuit generate a magnetic field.
The simplest electromagnet is a straight wire. The magnetic field circles around the wire when there is current flowing through the wire.
When you use the wire to make a loop, you increase the magnetic force. Many loops together result into a coil, which has a much stronger magnetic force.
If you place an iron rod in the coil, it becomes magnetized and makes the eletromagnet even stronger.
A generator is a device that generates an electric current by spinning an electric coil between the poles of a magnet. Energy is used to rotate the axle then as the coil moves through the magnetic field, the margentic forces push on its electrons and generate an electric current. Whenever the coil passes the pole of a magnet the direction of the current changes. This kind of current that regularly changes direction is called alternating current (AC). In US, generators produce alternating current that changes direction 120 times every second.
A DC generator is much the same as a DC motor, and is often called a dynamo. The spinning armature produces the electricity (if electricity is passed through a DC generator, it will spin like a motor). The armature is connected to a split ring commutator which enables this type of generator to send current through a circuit in only one direction. The DC generator’s pulsating electricity is produced in one direction - referred to as direct current - and coincides with the spinning of the generator.
Current electricity is first conducted to a transmission substation. The substation has many towers with power lines leaving them. Step-up transformers in the substation increase the voltage of the current electricity. This allows the electric charge to be transmitted over long distances more efficiently.
Electric Motors: Electric motors convert electric energy to mechanical energy. An electric motor is constructed in exactly the same way as a generator. Instead of producing electricity, it uses electrical energy to make a wire coil spins between the poles of a magnet. Faraday constructed the first motor. By coiling (copper) wire around a (iron) metal core a strong electromagnet can be made. When attached to an electrical source it will produce a strong magnetic field. To keep this electromagnet spinning in a magnetic field, the direction that the current is traveling through the coil must be switched. This is accomplished by with a gap, which allows the polarity of the electromagnet change just before it aligns with the permanent magnet.
DC motors use a commutator (a split ring that breaks the flow of electricity for a moment and then reverses the flow in the coil, when the contact is broken, so is the magnetic field) and brushes (contact points with the commutator) to reverse the flow of electricity through the magnetic field. The armature (the rotating shaft with the coil wrapped around it) continues to spin because of momentum, allowing the brushes to come into contact once again with the commutator.
AC motors have a rotating core, or rotor, made up of a ring of non-magnetic conducting wires connected at the ends and held in a laminated steel cylinder. Surrounding the rotor is a stationary component called a stator. The stator is a two-pole electromagnet. When the motor is turned on, the attraction and repulsion between the poles of the stator and the rotor cause the rotor to spin.
The high voltages that are used in transmitting current electricity over distances are dangerous. Therefore, before current electricity enters your home, the voltage is decreased at several stages.
Transformers are again used to change the voltage of the current electricity. A step-up transformer increases voltage at the generating plant prior to distribution to the power grid over high voltage transmission lines. Step-down transformers decrease the voltage of the electric charge. By the time the electric current reaches your home, the voltage is 240V.
Electrical power enters a meter on the side of your house where electrical usage is recorded. Power is then routed into the service panel. The main circuit breaker shuts off all the power in the house at once, in case of an overload. The individual circuit breakers in the service panel control the branch circuits, located throughout the entire house. Each branch circuit is connected in parallel to wall plugs, lights and wall switches within a particular area of the house.
A regular wall socket in your home delivers 120V, and this is what most appliances need to operate. Sockets that deliver higher voltage are used for specially designed appliances, such as certain types of clothes dryers, stoves/ovens or air conditioners.
Power is defined as energy per unit time. Electric power describes the amount of electric energy that is converted into other forms of energy (heat, light, sound, or motion) every second. The formula that is used is: Power (watts) = Energy (joules) / Time (seconds) A kilowatt is 1000 watts.
The power rating of a device can be used to determine the amount of energy the device uses. Multiply the power rating by the time the device is operating.
(E) Energy in joules, (P) Power in watts, (J/s) (t) time in seconds.
E = P x t
P = E / t
t = E / P
Kilowatt Hours is used as a unit for energy. The energy calculation is the same, except that hours are substituted for seconds and kilowatts (kW) are substituted for watts. Electricity meters measure the energy used in kilowatt hours and then bills you for every kilowatt hour used.
Energy is neither created nor destroyed. It doesn't appear and then disappear, but is transformed from one form to another. Most of the energy transformed in a light bulb is wasted as heat. Known as the Law of Conservation of Energy, no device is able to be 100% efficient in transforming energy. Most often, the energy is lost, or dissipated as heat. The efficiency of a device is the ratio of the useful energy that comes out of a device to the total energy that went in. The more input energy converted to output energy, the more efficient the device is.
Efficiency ( % ) = useful energy output (J) x 100% / total input energy (J)
Fuel oil, natural gas, and coal are used in large thermo-electric generating plants to produce roughly 25% of North America’s electrical energy needs. Coal is mined, crushed into a powder, blown into a combustion chamber and burned to release heat. This heat boils water and superheats the resulting steam to a high temperature and pressure, which then turns a turbine. The turbine shaft rotates large electromagnetic coils in the generator to produce electricity.
Hydro-electric plants use falling water (gravity), and pressure to generate electricity. Large dams raise the water above the power plant (which is usually built inside the dam), near the base. A channel, called a penstock, directs the water (at high pressure) to a turbine. The turbine then converts mechanical energy to electrical energy. Although these hydro-electric plants appear to be doing no harm to the environment, the reservoir they have to create behind the dam, destroys habitat and displaces whoever lived in the area prior to the reservoir being created.
Energy from Atomic Reactions: Bombarding uranium atoms with tiny particles, called neutrons cause the uranium to split into two smaller atoms. This is called nuclear fission. The process creates a huge amount of energy, which is used to generate electricity in a thermonuclear plant.
All thermonuclear and thermo-electric-generating plants release thermal energy into the environment. 43% of the water used in the cooling process enters the environment. Thermal pollution occurs when this heated water is not cooled before it re-enters the water system.
Cogeneration is the dual generation of electrical and thermal energy. The cogeneration systems usually are associated with industries, or commercial complexes.
Wind - this energy is harnessed by large propeller-type blades, which turn a shaft - connected to a generator.
Sunlight - Solar cells (made from silicon) enable the energy from the sun to be transformed (photoelectric effect) into electricity.
Tides - moving water can power turbines, which then run generators. When the tide comes in, the water is trapped in large reservoirs and then allowed to flow out past turbines.
Geothermal - Heat from the Earth's core can also be used to generate electricity. This geothermal energy (hot water and steam) is channeled through pipes to drive turbines - connected to generators, which produce the electricity.
Myths, folklore and legends were used to explain what ancient people observed in the night sky. First Nations people of the Pacific Northwest – believed the night sky was a pattern on a great blanket overhead, which was held up by a spinning 'world pole' resting on the chest of a woman named Stone Ribs. Aboriginal tribes – Algonquin, Iroquois and Narragansett believed the constellation Ursa Major was a bear running from hunters. Inuit in the high Arctic – used a mitt to determine when seal pups would be born, by holding the mitt at arm’s length at the horizon. Ancient Egyptians - The Sun God – Ra – was carried in a sacred boat across the sky every day. Solstice represents the shortest and longest periods of daylight. The Ancient Celts set up megaliths, in concentric circles, at Stonehenge to mark the winter and summer solstices. Ancient African cultures set large rock pillars into patterns to predict the timing of the solstices as well. The Mayans of Central America built an enormous cylinder shaped tower, at Chichen Itza, to celebrate the two equinoxes. The Ancient Egyptians built many pyramids and other monuments to align with the seasonal position of certain stars. Aboriginal Peoples of Southwestern Alberta used key rocks, which aligned with certain stars, in their medicine circles. Constellations are the groupings of stars we see as patterns in the night sky. There are 88 constellations and many are explained in Greek Mythology
Telescopes allow us to see objects that are very distant in space. In 1608, Hans Lippershey made one of the first telescopes – but it was Galileo Galilei who made practical use of it. The observations he made included:
The moon had blemishes (mountains and craters like the Earth).
Sun spots indicated that it rotates on its axis.
Jupiter’s moons orbit the planet.
Planets were disk-shaped, but because the stars were still pinpoints, they were further away.
Galileo’s Approach to Inquiry: Galileo’s observations supported Copernicus’s Sun-centered model but not Ptolemy’s Earth-centered model. The reason for his beliefs was that, the moons he observed orbiting Jupiter, indicated that the earth was not the centre of the universe.
The first telescope designed was a simple refracting telescope. It uses two lenses to gather and focus starlight. Reflecting telescopes use mirrors instead of lenses to gather and focus the light from the stars. A process called 'spin-casting' today makes mirrors, by pouring molten glass into a spinning mould. The glass is forced to the edges, cooled and solidified.
Refracting telescope
Reflecting telescope
To improve the views of space, astronomers are able to access images from a telescope in space. Free from the interferences of weather, clouds humidity and even high winds, the Hubble Space Telescope, launched in 1990, orbits 600 kms above the Earth, collecting images of extremely distant objects. It is a cylindrical reflecting telescope, 13 m long and 4.3 m in diameter. It is modular (parts can be removed and replaced) and is serviced by shuttle astronauts.
Isaac Newton stated the law of universal gravitation eighty years after Kepler’s contribution about elliptical orbits of the planets. Newton’s law states that there is a gravitational force between all objects that pulls them together. An orbit is the result of the attractive force of gravity balancing the straightforward movement of a planet because of velocity.
Spectroscopy is the Science of Colour. Isaac Newton passed a beam of light through a prism to produce a spectrum of colors. If you pass the light through a narrow slit before sending it through a prism (a spectroscope is a device that does this) the spectrum will be in more detail. Joseph von Fraunhofer used a spectroscope to observe the spectrum produced by the Sun. He noticed dark lines, called spectral lines, but didn’t know what they meant. He found these spectral lines throughout the solar system.
The significance of the spectral lines was discovered about 50 years later when Kirschoff and Bunsen, two chemists used a spectroscope to observe various chemicals when they were heated. They found some of the lines missing in some of the chemicals. Each particular element had its own unique spectral lines. This led to the science of spectroscopy – the study of spectra, as a part of chemistry. They found that there were three types of spectra.
Astronomers refract the light from distant stars to determine what the star is made of. Stars have dark bands in distinct sequences and thicknesses on their spectra. Each element that is present in the star creates its own black-line ‘fingerprint’. By attaching spectroscopes to their telescopes, astronomers are able to observe a star’s spectra, but because the distant stars are much dimmer than our Sun, only some of the elements in the spectra can be identified. Those that cannot be identified remain as inferences, based on what astronomers know about certain types of stars.
A change in the pitch (frequency) of sound waves because they are stretched or squeezed is known as the Doppler effect. Changes in the sound waves can be measured to determine how fast and in what direction a light-emitting object is moving. The spectrum of an approaching star shows the dark bands shifting to the blue end of the spectrum, whereas, the shift is to the red part of the spectrum if a star is moving away from the Earth.
Law enforcement officers detect the speed of an approaching vehicle by using a radar gun, which sends out a radio signal and receives one back from the vehicle. To determine the speed of the vehicle, the hand-held device records the difference in the outgoing wavelength and incoming wavelength.
Bigger telescopes enable astronomers to discover new bodies in space. Sir William Herschel built a huge reflecting telescope and discovered the planet Uranus with it in 1773. The largest refracting telescope was built at the Yerkes Observatory near the end of the nineteenth century. With it, Gerald Kuiper discovered methane gas on Saturn’s moon, Titan, and two new moons of Uranus.
To improve the views of space, astronomers are able to access images from a telescope in space. Free from the interferences of weather, clouds humidity and even high winds, the Hubble Space Telescope, launched in 1990, orbits 600 kms above the Earth, collecting images of extremely distant objects. It is a cylindrical reflecting telescope, 13 m long and 4.3 m in diameter. It is modular (parts can be removed and replaced) and is serviced by shuttle astronauts.
The technique of using a number of telescopes in combination is called interferometry. When working together, these telescopes can detect objects in space with better clarity and at greater distances than any current Earth-based observatory.
Telescopes enable astronomers to see further into space and identify distant stars. The problem they still have is how far are they from the Earth? The answer to this question lies in two methods. Triangulation and Parallax are two ways to measure distances indirectly, on the ground, or in space.
Triangulation is based on the geometry of a triangle. By measuring the angles between the baseline and a target object, you can determine the distance to that object. To measure the distance indirectly, you need to know the length of one side of the triangle (baseline) and the size of the angles created when imaginary lines are drawn from the ends of the baseline to the object.
Parallax is the apparent shift in position of a nearby object when the object is viewed from two different places. Astronomers use a star’s parallax to determine what angles to use when they triangulate the star’s distance from the Earth. The larger the baseline, the more accurate the result. The longest baseline that astronomers can use is the diameter of Earth’s orbit. Measurements have to be taken six months apart to achieve the diameter of the orbit.
With the development of radio telescopes, astronomers gain an advantage over optical telescopes, because they are not affected by weather, clouds, atmosphere or pollution and can be detected day or night. Much information has been gained about the composition and distribution of matter in space, namely neutral hydrogen, which makes up a large proportion of matter in our Milky Way galaxy.
Radio telescopes are made of metal mesh and resemble a satellite dish, but are much larger, curved inward and have a receiver in the center. In 1932 Karl Jansky built a radio antenna that was able to identify radio waves from space. Grote Reber built a radio dish based on Jansky’s antenna findings, where he 'listened' to the sky during the 1930’s. He discovered that the strongest radio waves came from specific places in space. The static Rober heard became louder when he tuned into these radio objects. The loudest being our Sun in the Milky Way Galaxy.
Radio telescope waves provide data, which astronomers graph, using computers to store the data and false color it to produce images of the radio waves, which are coded to the strength of the waves. Blues for low intensity, and as the signal gets stronger the colors go through greens, yellows, reds and whites. Radio observations have provided a whole new outlook on objects we already knew, such as galaxies, while revealing pulsars and quasars that had been completely unexpected.
Telescopes can now be connected without wires, thanks to computers and clocks. This method is called Very Long Base Interferometry ( VLBI ). With this technique, images 100 times that of the largest optical telescope can be captured. This is done by capturing images from any or all radio telescopes in the world.
The science of rocketry relies on the basic principle that For every action – There is an equal and opposite reaction. There are three basic parts to a Rocket:
The structural and mechanical elements are everything from the rocket itself to engines, storage tanks, and the fins on the outside that help guide the rocket during its flight.
The fuel can be any number of materials, including liquid oxygen, gasoline, and liquid hydrogen. The mixture is ignited in a combustion chamber, causing the gases to escape as exhaust out of the nozzle.
The payload refers to the materials needed for the flight, including crew cabins, food, water, air, and people.
Rockets need combustible fuel to make them fly. All fuels create exhaust which comes out the end of the rocket. The speed of the exhaust leaving the rocket is called the exhaust velocity, which determines the range of the rocket. The gravitational escape velocity had to be achieved (28,000 km/h), if humans were to venture into space. Robert Goddard launched the first liquid fuel rocket in 1926. The rocket was staged (having more than one section that drops off once its fuel is used up, making the rest of the rocket lighter and able to fly higher.)
In the 1960’s the Americans and the Russians were racing to launch spacecraft into orbit using rockets. They needed to use computers to calculate and control their orbits. The first computers on the ground (which filled large rooms) controlled the spacecraft in orbit. As computers became smaller they were put onboard the spacecraft and worked with computers on the ground to control the flight. Their vital role was to calculate orbits, locate satellites (and space junk), collect, store, and analyze data and to maneuver around these obstacles in orbit.
A technique called gravitational assist is a method of acceleration which enables a spacecraft to achieve extra speed by using the gravity of a planet. The planet’s gravity attracts the craft causing it to speed up and change direction (a slingshot effect), sending it on to the next planet.
Satellites can be natural – small bodies in space that orbit a larger body (the Moon is a satellite of the Earth ), and they can be artificial – small spherical containers loaded with electronic equipment, digital imaging and other instruments that are launched into Earth’s orbit to perform one of four functions:
1. Communication Satellites
These satellites provide 'wireless' technologies for a wide range of applications. Digital signals have resulted in clearer communications and more users
2. Satellites for Observation and Research
A geosynchronous orbit is one that enables a satellite to remain in a fixed position over one part of the Earth, moving at the same speed as the Earth. Numerous applications are now possible including:
Monitoring and forecasting weather
LANDSAT and RADARSAT (are not in geosynchronous orbit) – follow ships at sea, monitor soil quality, track forest fires, report on environmental change, and search for natural resources.
Military and government surveillance
3. Remote Sensing
Those satellites in low orbits perform remote sensing – a process in which digital imaging devices in satellites make observations of Earth’s surface and send this information back to Earth. The activities include providing information on the condition of the environment, natural resources, effects of urbanization and growth.
4. Personal Tracking Devices
The Global Positioning System (GPS) allows you to know exactly where you are on the Earth at any one time.
A solar system is made up of a star and the objects that orbit around it. In our solar system, there are eight planets orbiting the Sun. A planet is a large object that orbits a star. Form neares to the sun, the planets in our solar system include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The planets travel around the sun in elliptical or nearly circular orbits.
The inner planets are closer to the Sun than the asteroid belt and have surfaces made of rock. These planets are Mercury, Venus, Earth, and Mars. The outer planets are beyond the asteroid belt and have surfaces made of gases. These planets are Jupiter, Saturn, Uranus, and Neptune. Pluto was once known as the ninth planet. Pluto’s elongated orbit and small size were different from the other planets. Because of this, scientists debated whether Pluto should be classified as a planet. In Aug 2006, the International Astronomical Union officially reclassified Pluto as a dwarf planet. Other dwarf planets include Ceres and 2003 UB313, which is larger than Pluto but farther from the Sun.
Planet's unique features:
Jupiter: has the great red spot (aka red eye), which is a huge storm that has been blowing for over 400 years. It is believed that combination of sulfur and phosphorus are in Jupiter's atmosphere gives this storm its red color.
Saturn rings: First observed by Galileo in 1610. They are made of ice and rocks ranging in size from pea size to rocks larger than a house. Jupiter, Uranus and Neptune also have faint rings that are more difficult to observe.
Venus: The surface of Venus shows evidence of violent volcanic activity in the past. Venus has shield and composite volcanoes similar to those found on Earth. Long rivers of lava have also been observed on Venus.
Mars rocks! The dark boulders on the surface of Mars are volcanic rock fragments that have been found on Mars. These rocks look similar to rocks found near lava flows on Earth.
A moon is a natural object (natural satellite) that orbits a planet. Different planets have different numbers and sizes of moons. Generally, the outer planets have more moons. The Earth has only one moon while Jupiter has at least 63 moons. Saturn has 47 moons, Uranus has 27 and Neptune has 13.
An artificial satellite is an object that is put in space by man to orbit around the earth or other planets. These may be to monitor weather or conduct various forms of communication.
Moons vary in size. Ganymede is the largest moon in the solar system. In fact Ganymede is larger than Pluto and Mercury. The Earth's moon is also larger than Pluto and is clearly visible without a telescope.
When small objects in space collide with larger objects, a crater is formed. Craters are bowl-shaped holes on the larger object.
A comet is a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun.
An asteroid is a rock that revolves around the Sun. Most of the thousands of asteroids in the solar system are located between Mars and Jupiter in the asteroid belt.
An object that crosses paths with Earth and enters the atmosphere is called a meteor. Most meteors burn up before they reach the ground. When a meteor lands on the ground, it is called a meteorite.
Chelyabinsk meteor - 2013
A star is an object that produces its own heat and light energy. Stars go through stages from beginning to ending depending on how much hydrogen tha star contains. The star's cycle ends when it stops giving off energy.
All stars form out of a nebula. A nebula is a cloud of gases and dust. Gravity pulls the mass of nebula, which contains a lot of hydrogen atoms and as the atoms move closer they collide with each other producing heat. The temperature increases and when the temperature reaches 10 million degrees Celcius, the hydrogen atoms combine to form Ehlium. This process produces huge amounts of heat and light. This marks the beginning of the formation of a star.
The sun is a star, like other stars, it uses hydrogen as the source of energy. As the heat in the sun increases, it forces the hydrogen at the endge of the sun to expand into space, as the hydrogen moves further away from the center of the sun, it cools slightly and turns red. This stage of the star is called a red giant.
The Sun is 1.4 million km in diameter. Its temperature is about 15 million degrees Celsius. 600t of hydrogen are converted, by nuclear fusion, into helium per second. This is the energy released from the Sun. The Sun emits charged particles in all directions. This solar wind bombards the Earth at 400km/s, but the magnetic field of the Earth protects us.
Eventually, all the helium is gone and the star begins to cool off and shrink becoming a white dwarf. A white dwarf is a small dense star that sines with a cooler white light. This is the end of the cycle for medium sized stars.
Stars that start with larger amounts of hydrogen (larger stars) end their cycle differently. After they become red giants the atoms at the core become so hot that they combine to form iron atoms. Eventually the iron gets so hot and explodes into a supernova. Supernovas shine brightly for days or weeks then they fade away.
If a star is very massive, it may end its life as a black hole. A black hole is an object that is so dense and has such powerful gravity that nothing can escape from it,not even light.
The sun is a medium sized star with a temperature of around 6000 degrees celcius. Giant stars are about 100 times larger than the sun and super giant stars are 1000 times larger. Neutron stars are the smalles stars.
Stars that form patterns are called constellations. Constellations were often named after animals, characters from stories, or familiar objects. Some constellations have been extensively useful to both ancient and modern travelers. For example, if you can see either the Big Dipper or the Little Dipper in the night sky, you can follow the line that their stars make to find Polaris, the North Star. If you travel in the direction of Polaris, you will be moving north. If you ever become lost in the woods or at sea, look for Polaris (North star) in the night sky. It will help guide you to safety.
The ancient Greeks divided the sky into 12 sections. They named some constellations after characters from Greek myths, such as Orion, a hunter, and Hercules, a hero.
Light Years
After the sun, the next closest star is called Proxima Centauri and is about 40,000,000,000,000 km away. This distance is so huge and becomes difficult to remember and comprehend. We can use the unit light year, which is equal to the distance that light travels in a year, and is equal to 9.5 billion kilometers. Proxima Centauri is 4.2 light years away from the earth.
Clusters and Binary Stars
Some stars form clusters that may contain more than 100,000 stars. Clobular clusters are shaoed like a sphere. When two stars are close to each other, or somehow overlap and are seen as though they were only one star, they are called binary stars. the prefix -bi stands for 'two'. A star that seems to be blinking might actually be a binary star where one of the stars, the dimmer one, blocks the light from the brighter star.
Galaxies
A galaxy is a huge very distant collection of stars. Each galaxy holds billions of stars.
Galaxies differ in size, age, and structure. Astronomers place them in three main groups based on their shapes: spiral, elliptical, and irregular.
A spiral galaxy looks like a whirlpool. The spiral arms can be tightly or loosely wound around the galaxy’s core, and they often contain a great deal of dust. Some spiral galaxies are barred galaxies. A barred galaxy has a “bar” of stars, gas, and dust through its center. The spiral arms emerge from this bar.
An elliptical galaxy is shaped a bit like a football. It has no spiral arms and little or no dust.
An irregular galaxy has no recognizable shape. The amount of dust and gas varies. The irregular shape may have been caused by collisions with other galaxies.
Our solar system is part of the galaxy called the Milky Way. The stars you see in the sky are part of the Milky Way galaxy. The Milky Way is a spiral galaxy. The stars are grouped in a bulge around a core. All of the stars in the Milky Way, including our Sun, orbit this core. The closer a star is to the core, the faster its orbit is. Several spiral arms extend out from the core. Our solar system is located on one of these spiral arms. The arms contain most of the Milky Way’s gas and dust. We cannot see the center of the Milky Way, because there is dust between us and the core. However, from Earth we can see more stars when we look in the direction of the galaxy’s center than when we look in other directions.
The Big Bang Theory
The Big Bang Theory hypothesizes that the universe started with a big bang a single point and has been expanding ever since. Scientific evidence indicates that the big bang happened 13.7 billion years ago.
Astronomers think the galaxies must have been closer to each other in the past. The early universe was very dense, and its temperature was high. At the beginning moment, the universe was extremely tiny, hot, and dense. From this tiny beginning, the universe expanded rapidly. This expansion sent matter out in all directions.
The galaxies continue to move outward. Evidence for the big bang comes from background radiation. Background radiation comes from all directions in space. This radiation is left over from the beginning moments of the universe.
How did Earth form?
Scientists think that Earth is about 4.6 billion years old and theorise that the Earth and its atmosphere developed in a series of stages. The process began in the nebula that formed the Sun. Dust and ice particles moved within the nebula, occasionally colliding. They merged and stuck together. The clumps of particles grew until they became the young Earth, or proto-Earth. Over time, proto-Earth became large enough that its gravity could hold an atmosphere. Scientists believe that the atmosphere did not initially contain oxygen, as it does today. Atmospheric oxygen developed as a waste product of photosynthesis.
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