Science Reasoning Test Do’s and Don’t’s
A list of Do’s:
Preview, read, review. Think of the Science Reasoning Test as just a specialized version of the regular ACT Assessment Reading Test. Use the same skills and strategies detailed in that section, mark up the test booklet to underline main ideas, and remember that all the information you need to answer the question is right there.
Read just the labels, legends, and explanatory sidebars. On all forms of data representation, read the labels on the axes, rows, and columns, as well as the legends and Sidebars. You don't have to read the actual point-by-point information. Notice trends, groupings, processes, and sequences, and then move on.
Find the main ideas as you read. In Data Representation passages, focus on what is being measured, on relationships among the variables, and on trends in the data. In Research Summary passages, focus on the question of the hypothesis, on the variables being tested, and on differences in the experimental results. In Conflicting Viewpoints passages, focus on what must be explained, on similarities and differences in the theories presented, and on hidden assumptions that underlie each theory.
Know what's being asked. Is it Experiment 3 the question asks about or Experiment 4? Table 1 or Table 2? Read carefully. Just a few words can mean the difference between the correct answer and an incorrect one.
~ay close attention to the last sentence of the introductory material. In a Data Representation passage, the last sentence of the introductory material is where the relationship between the variables can usually be found. In a Research Summary passage, it's where the purpose of the experiments can usually be found. In a Conflicting Viewpoints passage, it's where the question under consideration can usually be found.
Look for differences in the data. Remember that differences are more important than similarities. when comparing charts, tables, experimental design, experimental results, and so on, look for the differences. Questions are more likely to deal with differences than similarities.
Know the four type of questions. Decide whether a question is about the main idea, details, an inference, or an application. Your approach to each will be slightly different.
Look for the change. In any experiment, look for the variable that changes, then look to see how a change in the variable results in changes in other elements of the experiment.
A list of Don'ts:
Don't get lost in numbers, scientific jargon, and irrelevant details. Don't try to memorize the details as you read. Just look for the main ideas. You can then refer back to the passage to find the few details needed to answer questions.
Don't be thrown by math on the Science Reasoning Test. Math on the Science Reasoning Test is very basic, and you won't be allowed to use a calculator. If you think a particular item calls for extensive calculations, you are probably misreading the question.
Don't confuse units of measurement. Athough math is secondary, it does have its role. You might be asked, for example, to take a relationship expressed in liters and apply it to a quantity of milliliters; remember to change the unit of measurement.
Don't take sides in Conflicting Viewpoints passages. Deciding which side is right or which side you agree with is irrelevant. Trying to figure that out only wastes time and has nothing to do with the questions being asked. Focus on the information presented and the assumptions supporting each theory.
Don't accept every assumption as true. Certain experiments will be based on faulty assumptions. If the assumption is faulty, the experimental design is faulty, and the results do not prove what the conclusion claims to prove.
TIP
Even though you can't use a calculator on the Science Reasoning portion of the ACT Assessment, you shouldn’t have much trouble with the math-it's usually fairly easy in this section. And, feel free to round off numbers and estimate, especially when answer choices have broad differences.
SCIENTIFIC TERMS AND CONCEPTS MOST LIKELY TO BE ON YOUR ACT ASSESSMENT
| Chemistry | Biology | Earth/Space Science | Physics |
The following terms and concepts have been chosen as those most likely to appear on the ACT Assessment Science Reasoning Test. The terms are drawn from the fields of biology, chemistry, earth sciences, and physics. The test makers know you might not have studied a specific field, for example, physics. However, in the minimum two years of high school science you've presumably taken, you have probably been exposed to most
of these words. You should have the broad background of scientific knowledge necessary to give you some understanding of the term when it's put in the context of a Science Reasoning passage.
This list is a helpful way to refresh your memory of crucial science topics you've studied throughout your high school years. It'll also highlight for you the topics or areas in which your background is strongest and weakest.
How to Use Your Scientific Terms List
Go down the list and check every word you don't know or are hesitant about. If the following definition is not sufficient to jog your memory, you might want to review the relevant topics using your favorite science textbook or study guide. Because you tend to remember information you like, the terms have been broken down into the four fields of biology, chemistry, earth sciences, and physics. This way you can quickly pinpoint areas that need attention.
Assuming you've allowed yourself three months or more, work on about 10 minutes' worth of words each day. If you wish, write the definition of each unfamiliar word into a notebook to make your own Scientific Terms journal.
Putting the definition in your journal will help you remember the word better when you see it again on the ACT Assessment.
Scientific Terms and Concepts Glossary Chemistry
acid-a substance capable of donating hydrogen ions. This is called the Bronsted-Lowry definition. Alternately, the Lewis definition says that an acid is any species that accepts electron pairs. This definition is more general. Acids have a sharp, sour taste; vinegar is an example.
activation energy-the minimum energy required between two molecules for a reaction to occur.
atom-the smallest unit of an element, composed of electrons, protons, and neutrons, that still has all the properties of that element.
atomic mass-the average mass of the atoms of a given element. Atomic mass is measured in atomic mass units. One atomic mass unit has been set at one-twelfth the mass of the carbon-12 atom.
Avogadro's constant-the number of atoms in one mole of pure substance.
Avogadro's number-the number of atoms in 12 grams of carbon-12, equal to 6.022 x 1023. This constant is used in various chemical and physical calculations and formulas.
base-a substance capable of accepting hydrogen ions. This is known as the BronstedLowry definition. (By corollary, bases dissolved in water increase the amount of hydroxide ion [OH].) Alternately, the Lewis definition says that a base is any species that donates lone-pair electrons. This definition is more general. Bases are slippery.
boiling point-the temperature at which the liquid and gas phases of a substance are in equilibrium.
buffer-a solution that maintains a constant pH despite the addition of small amounts of acid or base. A buffer is usually made by mixing a weak acid with its conjugate weak base.
calorie- the amount of heat required to raise one gram of water one °C. 1 calorie = 4.184 J
catalyst-a substance that speeds up a chemical reaction. The catalyst itself is not a reactant and undergoes no chemical change.
chromatography-a method of fractionation in which a mobile phase containing the mixture to be separated is passed over a stationary phase that displays some affinity for the materials in the mobile phase. This affinity may be based upon polarity, size, or some form of reversible binding ability (such as between an enzyme and its substrate) The stationary phase must be carefully chosen so as to maximize the differences in affinity for the various substances in the mobile phase.
compound-a substance containing two or more elements.
concentration-the ratio between solute and solvent in a solution.
conservation of mass-the law that states that in every chemical reaction there must be an equal quantity of matter before and after the reaction.
covalent bond-a bond formed between two atoms by the sharing of electrons.
crystal-a solid in which the particles are arranged in a repeating geometrical patterns.
electron-a negatively charged subatomic particle.
empirical formula-the chemical formula of a compound that shows the relative pumber of moles of each element in terms of the smallest integers. Thus, the empirical formula shows the ratio of elements within a compound.
energy-a property of matter that describes the ability to do work. Energy takes many forms, including potential energy and kinetic energy (see enthalpy).
enthalpy-a measurement of the energy of a system due to the movement of its particles. At constant pressure, the enthalpy change of a system is equal to the heat absorbed or released.
entropy-a measurement of the disorder of a system. A fundamental law is that the entropy of the universe is constantly increasing. However, in many reactions the entropy is decreased (i.e. the system is more ordered after the reaction than before). (Biological systems tend to employ reactions that increase the order of the system. To do this, they must create more disorder in the surrounding environment. This is one of_the reasons many reactions in biological systems require a great input of energy.)
fractional distillation-the separation of two or more components of a liquid solution on the basis of their different boiling points. This is done by repeated evaporation and recondensation of the components.
fractionation-the separation of a mixture into its parts.
free energy-the chemical potential energy of a chemical substance or system.
functional group-a group of atoms in a molecule (usually organic) that exhibit characteristic properties. Examples of functional groups commonly encountered are alcohols (-OH), aldehydes and ketones (-C=O; in ketones this group is internal), carboxylic acid (-COOH), and amines (-NH2).
gas-a phase of matter having no definite shape and a volume that is defined only by the size of the container. The gaseous phase is the most energetic phase for a given substance.
heat-the means by which energy is transferred from a hot object/substance to a colder object/substance.
hydrogen bond-the strong dipole-dipole interaction that forms between a hydrogen atom bonded to a strongly electronegative atom (such as oxygen) and a lone-pair electron on a nearby electronegative atom. Hydrogen bonds are very weak. (Millions of hydrogen bonds are constantly forming and unforming in a glass of water. These bonds are responsible for the special properties of water, such as its elevated boiling point.)
inhibitor-a substance that slows the rate of a reaction. There are three main types of inhibitors: competitive, uncompetitive, and mixed inhibitors.
ion-an atom or group of atoms that has gained or lost one or more electrons. This causes the atom or group of atoms to become either negatively or positively charged.
ionic bond-a bond formed through the attraction of two ions of opposite charge.
isomers-two forms of a chemical compound that have the same chemical formula but a different spatial configuration or structure.
liquid-a phase of matter in which a substance has no definite shape but has a definite volume. Matter in the liquid phase has a kinetic energy intermediate between that of mass in solid phase and mass in the gaseous phase.
lone-pair electrons-an unshared pair of electrons in the outermost orbital of an atom.
mass-the measure of the amount of matter.
matter-anything that has mass and takes up space.
melting point-the temperature at which the liquid and solid phases of a substance are in equilibrium.
molality-the number of moles of solute present per kilogram of solvent. Because one kilogram of water has a volume of one liter, molality is also the number of moles of solute present per liter of water, and the molality and molarity of such solutions are equal
molarity-The number of moles of solute present per liter of solution.
mole-The amount of a substance consisting of Avogadro's number of elementary particles (atoms or molecules). Therefore, one mole of any substance contains 6.022 x 1023 elementary particles.
molecule-the smallest particle of a substance that retains the chemical and physical properties of that substance and is composed of two or more atoms.
molecular formula-the chemical formula of a compound that specifies the actua number of atoms of each element in a compound.
molecular mass-the mass of a molecule, found by summing the atomic masses of eac of the atoms within the molecule.
neutron-a neutrally charged subatomic particle.
nucleus-the small, positively charged center of an atom composed of protons and neutrons.
orbital- one of several spaces around the nucleus of an atom, each of which can be occupied by up to two electrons. All the electrons in a given orbital must have the same energy level, energy sublevel, and spatial orientation.
oxidation-the loss of electrons.
pH-a measure of the hydronium ion concentration in a solution. pH = -log[H30]+.
polarity-asymmetrical charge distribution over a molecule. Such a molecule is called a dipole.
pressure-the force exerted by moving particles on a specified unit area. Thus, pressure may be expressed as pounds (the force) per square inch (the unit area).
proton-a positively charged subatomic particle.
reaction rate-the speed at which reactants are converted into products in a chemical reaction.
reduction-the gain of electrons.
salt-a compound consisting of the positive ion of a base and the negative ion of an acid.
solid-a phase of matter in which a substance has definite shape and volume. The atoms in a solid have the lowest kinetic energy of the three phases, because their molecules are relatively fixed in space.
solution-a homogeneous mixture of a solute and solvent. The solute is that which is dissolved in the solvent.
temperature-a measure of the average kinetic energy of molecules.
titration-a technique in which small amounts of an acid or base of known concentration and pH are added to a solution in order to determine the pH of the solution. By using an indicator or a pH meter, the experimenter can observe the change in pH caused by these additions, and from this data and from the known pH and volume of acid or base added, the pH of the solution can be determined.
van derWaals forces-weak forces of attraction between two molecules. These forces do not result in a bond. Rather, they represent the attraction of the electrons of one atom for the protons of another, in much the same way opposite pole of a magnet attract each other.
alternation of generations-The succession of haploid and diploid phases in a sexually reproducing organism. In most animals, only the gametes are in the haploid phase. In fungi, algae, and plants, the haploid phase may be the dominant phase, although in vascular plants the diploid is dominant.
amino acid-a compound made up of carbon, hydrogen, nitrogen, and oxygen and containing one of more than 20 different possible side groups. The general formula for amino acids is H2N-CHR-COOH, where R is the side group.
asexual reproduction-reproduction involving the cells of only one parent. As such, there is no fusion of nuclei and no transfer of genetic material. Thus the offspring is genetically identical to the parent. There are five types of asexual reproduction: binary fission, budding, sporulation, regeneration, and vegetative reproduction.
autotroph-an organism which manufactures organic food from inorganic sources. Plants are autotrophs.
carbohydrate-a compound made up of carbon, hydrogen, and oxygen with the general formula Cn(H20)m. Carbohydrates are commonly known as sugars and are the primary sources of cellular energy. Examples of carbohydrates are starch and cellulose.
cell-the basic unit of organization in all living things. Any cell is surrounded by a plasma, or cell, membrane, which separates the interior environment from the exterior and regulates the passage of materials into and out of the cell. All cells also must contain the hereditary material of the cell and some structures capable of processing energy. There are two distinct types of cells: prokaryotic cells and eukaryotic cells.
chemosynthesis-the process by which chemical energy is trapped and converted into usable forms of energy. Nitrogen-fixing bacteria do this.
chromosome-a structure composed of DNA and protein that contains some or all of the genetic material of a cell.
circulation-the process by which materials are transported throughout the body The circulatory system in humans consists of the blood vessels (arteries, veins and capillaries) and the heart. This system is a closed circulatory system. Some lower ammals, such as the hydra, have an open circulatory system.
diffusion-the process by which molecules pass across a porous membrane. Diffusion may be passive, in which case the molecules cross from the region of highest concentra tion to the region of lowest concentration, or either facilitated or active, in which case the passage is helped in some way so as to not be entirely dependent upon t~e~ concentration.
digestion-the process by which large, insoluble molecules are broken down into small, soluble molecules. Digestion may be intracellular or extracellular.
DNA-the fundamental hereditary material of all living organisms. George Watson and Francis Crick elucidated the double-stranded nature of the DNA molecule and the helix structure it assumes. DNA molecules make up the gene. DNA molecules are composed of nucleotides, which consist of a 5-carbon sugar (deoxyribose), a phosphate, a> nd a nitrogen base. The nitrogen base determines the nucleic acid. In DNA, there are four types of nitrogen bases (adenine, thymine, guanine, and cytosine), and therefore four types of nucleic acids. These four bases also are the basis for the genetic code. Key to the continuation of life is the fact that DNA can reproduce with a high degree of accuracy
egestion-the removal of undigested material.
enzyme-a protein that acts as a catalyst in chemical reactions. Enzymes have binding sites on their surface, which is generally where the reaction occurs.
eukaryote-an organism whose genetic material is contained within a nucleus. All life-forms other than viruses and bacteria are eukaryotes.
evolution-the process by which organisms change from generation to generation. Evolution is a gradual change involving random genetic mutations. Charles Darwin suggested that genetic mutations resulting in physiological changes will sometimes confer an advantage to the organism over its competitors. This advantage leads to natural selection, which is the driving force behind all evolutionary change.
excretion-the removal of cellular waste products from an organism.
gene-a unit of a chromosome that contains all the genetic information to create a single polypeptide or codes for a trait.
genetics-the study of heredity, founded by Gregor Mendel. There are three main laws in genetics that Men del developed. The first is the Law of Dominance, which states that when organisms containing pure contrasting traits are crossed, only one of the traits will be expressed in the offspring. The trait that is expressed is the dominant trait; the trait not expressed is the recessive trait. The second law is the Law of Segregation, which states that alleles segregate during gamete formation and then recombine. The third law is the Law of Independent Assortment, which states that alleles on different genes assort independently during gamete formation.
genotype-the exact description of the genetic makeup of an organism.
heterotroph-an organism that obtains premade organic food from other sources. These organisms are unable to make organic food from inorganic sources. Animals are heterotrophs.
homeostasis-the maintenance of a steady state. ingestion-the process of taking in food.
lipid-a large, oily organic molecule composed of carbon, hydogen, and oxygen, which functions as energy storage and insulation. Examples are fats, oils, and steroids. Lipids can be converted into twice the cellular energy of carbohydrates, and are therefore used to store energy in the body.
meiosis-The process by which specialized reproductive cells in sexually reproducing organisms are created. These reproductive cells are called gametes, and they are special in that they are haploid (having only one set of chromosomes). Because normal cells are usually diploid (having two sets of chromosomes) meiosis involves the halving of the number of chromosomes. Meiosis occurs in two phases and results in four haploid cells.
metabolism-the process by which complex, high-energy compounds are broken down by organisms into usable forms of energy; includes catabolism and anabolism.
mitosis-the process of cell division in which the chromosomes replicate so that there are two exactly similar sets of genetic material in the cell. The cell then divides into two cells, with each cell taking one set of chromosomes. The result is two cells that are genetically identical.
nucleus-The centrally located chamber in eukaryotic cells that contains the chromosomes. It is bounded by a double membrane and is the information center of the cell.
nutrition-all the activities by which an organism obtains and processes materials necessary for energy, growth, reproduction, and regulation.
osmosis-the process by which water passes across a porous membrane. In osmosis, water will flow from a region with a low concentration of dissolved molecules to a region with a high concentration of dissolved molecules.
phenotype-the description of the observable traits in an organism. These traits are the result of the genetic makeup of the organism as well as environmental factors
photosynthesis-the process by which visible light is trapped and converted mt usable forms of energy. Plants and green algae do this. Photosynthesis occurs in tw reactions, the light and dark reactions. A by-product of the light reaction is oxygen~ Photosynthesis occurs in the chlorophyll of plants.
prokaryote-an organism whose genetic material is not contained within a nucleu but rather free in the cytoplasm. This is the simplest form of cell. Bacteria and virus are prokaryotes.
homeostasis-the maintenance of a steady state. ingestion-the process of taking in food.
protein-a compound made up of many amino acids linked together end to end. Proteins are integral to building many structural features in the cell. Enzymes are also proteins.
regulation-the coordination and control of life activities. In all animals, regulation involves chemical control. In higher animals, regulation also involves nerve control.
reproduction-there are two types of reproduction, asexual and sexual. Asexual reproduction involves only one parent. There are three main types of asexual reproduction; fission, budding, and spore formation. Sexual reproduction involves two parent cells. If these cells are the same, then the joining of these cells is called conjugation. If these cells are different, then the joining of these cells is called fertilization.
respiration-the conversion of chemical energy in food by oxidation into forms that can be used to drive the chemical reactions essential to life. The two types of respiration are aerobic and anaerobic respiration.
RNA-the material through which the genetic information in DNA is converted into the proteins for which it codes. RNA has a different 5-carbon sugar (ribose) and instead of the nitrogen base thymine it has uracil. RNA is single stranded. There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
sexual reproduction-reproduction in which the cells of two parents combine through the process of fertilization to produce a fertilized egg cell that develops into a new, genetically unique organism. During the process of fertilization, there is an exchange of genetic material that allows for genetic variation.
synthesis-the process by which materials necessary for energy, growth, reproduction, and regulation are made by an organism from energy sources obtained from the environment.
tissue-a group of similar cells that are organized into a single unit and that perform the same function. Tissue types in animals include epithelial (such as skin, and the linings of the lungs, digestive tract, and blood vessels), muscle, nerve, connectivel supportive, blood, and reproductive tissue. Tissues in animals group together to form organs. Tissue types in plants include conducting (xylem and phloem), growing, supporting, storage, and reproductive tissue.
transport-the process by which materials are absorbed and circulated throughout an organism.
vitamin-a compound that the body cannot synthesize for itself but that is necessary ~n small quantities for life functions. Vitamins come in a variety of structurally unrelated forms. Many vitamins work as co-enzymes (i.e. they are necessary to make certain enzymes active).
asteroid-a large celestial body composed mostly of rock. Asteroids usually are under the influence of a star's gravitational field, but have larger, more eccentric orbits than planets.
atmosphere-the gaseous layer that envelopes the earth. The thickness of the earth's atmosphere is about 1,100 km. It consists of three layers: the troposphere, the stratosphere, and the mesosphere. The earth's atmosphere is important in that it shields the earth from harmful radiation and excessive heat. It also prevents the earth from cooling too rapidly at night.
biosphere-the portion of the earth that supports life, including most of the hydrosphere, the lower portions of the atmosphere, and nearly all of the earth's surface.
climate-all the characteristics of weather, including precipitation, temperature, and humidity, which a particular region experiences over a long period of time. The averages of all these factors constitute the climate for a particular place.
community-all the microorganisms, plants, and animals inhabiting a given location that interact and are ecologically integrated.
compression cementation-the process by which sediment is cemented together into sedimentary rock due to the large compression forces exerted by heavy layers of overlying material.
condensation-the changing of water from a gas to a liquid, involving the removal of heat from the water. The heat is then released into the atmosphere in the form of latent heat, so called because the temperature remains the same during this process.
conduction-the transfer of heat through solids. This occurs because, when a solid is heated, its atoms will move faster. Random collisions between these atoms and those neighboring will cause the neighboring atoms to also move faster. This process repeats, until the heat has transferred across the solid.
convection-the transport of heat and moisture by the movement of a fluid
crystallization-the process by which igneous rock is formed from molten magma
depression-an area of low atmospheric pressure around which winds travel counte clockwise in the Northern Hemisphere and clockwise in the Southern Hemispher Depressions tend to occur when warm air meets cold air. Because the cold air is heavier than the warm air, the warm air rises above the cold, causing winds as well as cloud formation.
earthquake-a shifting of the rock layers of the earth's crust, most commonly cau by either the movement of tectonic plates or the eruption of volcanoes. Earthquakes emit two kinds of shock waves: P-waves and S-waves. P-waves travel through both liquids and solids, while S-waves travel only through solids.
ecosystem-all of the organisms of a particular habitat together with the environment in which they live.
electromagnetic energy-the energy exhibited by the earth due to its magnetic field.
environment-all of an organism's surroundings. This includes all of the species that influence the organism as well as temperature, humidity, light, and so on.
erosion-the physical process by which rocks are corroded and converted into other forms by the action of heat, cold, gases, water, wind, gravity, and plant life. The process of erosion is key to the formation of sedimentary rock and soil.
evaporation-the changing of water form a liquid to a gas. Heat must be added to the water in this process. (This is why your skin feels cooler when water evaporates from it.)
galaxy-a grouping of hundreds of millions of stars. All these stars interact gravitationally and orbit around a common center. The galaxy in which the earth exists is called the Milky Way galaxy.
geocentric model-the model of the solar system that sets the earth at the center of the solar system and has all of the celestial bodies rotating around the earth. This model is unnecessarily complicated and was eventually abandoned in favor of the heliocentric model.
geomagnetism-the magnetic phenomena exhibited by the earth and its atmosphere. The study of geomagnetism often centers on the study of the earth's gravitational field and the changes that occur in it.
greenhouse effect-the effect of atmospheric carbon dioxide, water, and other trace gases on the average temperature at the surface. This effect is caused by the absorption by these substances of energy radiated from the earth.
heliocentric model-the model of the solar system that has the sun at the center with the planets rotating around it. In this model, the apparent motion of the stars is explained by the rotation of the earth.
hydrological cycle (water cycle)-the cycle whose primary components are (1) the evaporation of moisture from the surface of the earth, due to the warming of the suns rays, (2) the carrying of this moisture into higher levels of the atmosphere, (3) the condensation of water vapor into clouds, and (4) the return of water to the surface as precipitation.
hydrosphere-the layer of water on the surface of the earth. This includes all the oceans, as well as the rivers, lakes, etc. It is estimated to cover about 70.8 percent of the earth's surface.
igneous rock-rock formed during the cooling and crystallization of a hot, molten fluid from the earth's core, called magma. Igneous rock makes up over 95 percent of the earth's crust.
infiltration-the process by which water passes into the earth through the soil.
lithosphere-the layer of the earth's crust composed of rock and extending for about 100km below the surface. The lithosphere is composed of two shells, known as the crust and the upper mantle. These are in turn divided into tectonic plates. See Tectonic Plate Theory.
mantle and core-the heavy interior of the earth, which constitutes most of the earth's mass. The core is composed of a molten layer surrounding a solid center. It is the source of much of the earth's heat. The mantle, on the other hand, is solid and rigid.
metamorphic rock-rock formed by the process of metamorphism, which involves partial melting and recrystallization of sedimentary or igneous rock. An example is marble, which is caused by the metamorphosis of limestone.
metamorphism-a process of structural change in rocks induced by heat and pressure.
meteorology-the study of the earth's atmosphere, specifically the day-to-day variations of weather conditions.
moon-a large celestial body travelling in orbit around a planet.
orbit-the path an object takes when travelling around a large body due to its gravitational force.
permeability-a measure of the rate at which water passes through particles. Permeability is dependant upon porosity, which is a measure of the amount of space between particles. Larger particles have a greater porosity and therefore a greater permeability.
planet-a large celestial body travelling in orbit around a star. There is currently much debate as to what exactly differentiates a planet from other large bodies in space, such as asteroids.
pollutant-any substance found in the environment in levels above that normally found and that may cause harm.
population-all the members of a species inhabiting a given location.
precipitation-the moisture that falls to the earth's surface. Examples are rain, snow, sleet, and hail.
radiation-energy absorbed by the earth's atmosphere from space. Most of the radiation we are subjected to comes from the sun, called insolation (short for incoming solar radiation).
runoff-the water that is unable to infiltrate the surface of the earth, and thus runs down into streams, rivers, lakes, and so on.
satellite-any object that travels around a large body (such as a planet or a sun) due to the gravitational forces exerted by that body upon the object.
sedimentary rock-rock formed from the products of weathering on other rocks. This happens when water and carbon dioxide break up and dissolve small pieces of rock.
solar energy-the energy released by the sun in the form of light, heat, and other types of radiation.
star-a large celestial body composed of incandescent gases, largely hydrogen and helium. A star radiates energy created by internal nuclear fusion reactions, in which two lighter atoms are fused to create a single heavier atom and a release of energy. Thus, hydrogen nuclei are fused to create helium (a process called hydrogen burning), and then helium nuclei are fused to eventually create carbon (helium burning). As a result of these reactions, the density of a star is constantly increasing as it ages, and its increasingly powerful gravitational field constantly causes it to contract.
sublimation-the change from a solid to a gas without passing through the liquid phase.
sun-a star that has planets orbiting within its gravitational field.
system-a grouping of planets, all rotating around a star (sun) due to the gravitational forces exerted by it.
Tectonic Plate Theory-the theory that states that the tectonic plates of the earth's crust and upper mantle move about, collide, and separate over time. Tectonic Plate Theory explains the relative positions of the continents and the formation of large mountain ranges such as the Himalayas, as well as natural phenomena such as earthquakes.
terrestrial radiation-the radiation of energy from the earth's surface into space. This generally occurs at night when temperatures are cooler.
transpiration-the process by which plants release moisture to the atmosphere.
weather-the state of the atmosphere at a particular time and place. Elements of weather include temperature, humidity, cloudiness, precipitation, wind, and pressure.
acceleration-the rate of velocity change over a given period of time. This is given by the equation a = AviAt. Because velocity is a component of acceleration, acceleration is a vector quantity (see vector).
amplitude-the distance from the crest or the trough to the center of a wave. angular acceleration-the change in angular velocity.
angular velocity-velocity around a circular path.
centripetal acceleration-acceleration toward a central point. When bodies move in a circular motion, their velocity at any one time is tangential to the circle. Thus, for the body to continue to move circularly, the velocity must constantly be moving toward the center. Thus, it is accelerating toward the center. This acceleration is what accounts for centripetal force.
conductor-something through which electric charges may move. Conductors, however, vary in terms of how easily they allow charge to move through. This is because of resistance.
diffraction-the bending of waves caused when a wave encounters an opening that is the same size as its wavelength.
efficiency-as applied to an engine, the ratio of the net work done by the system to the heat added to the system at the higher temperature.
electric charge-a fundamental measure based upon the idea that the electron represents a negative charge. Charge is measured in coulombs, where one coulomb equals 6.25x 1018 electrons. Charge can either be negative or positive, depending upon whether it is likely to repel or attract electrons.
electric current-in a circuit, the amount of charge flowing past a certain point per unit of time. Current is represented by the letter I and is measured in amperes or coulombs per unit time. Thus, I = Q/T where Q is charge.
electric field-that region in space in which a charge can experience an electric force' Electric fields can act to move charges from one point to another.
electric force-the force generated between charges as a result of the repulsive attractive characteristics described in the Law of Electrostatics.
electromagnetic induction-the creation of a magnetic field as a result of the flow of an electric current.
force-any phenomena that pulls or pushes a mass. Force is a vector quantity, described by the formula F = ma.
frequency-the number of cycles of a wave that pass a particular point per unit time (second).
gravity-the force that pulls masses toward the earth. Gravity accelerates all masses at 9.8 mIs2 and is always perpendicular to the surface of the earth.
inertia-the characteristic of mass that dictates that the motion of a mass will not change unless an outside force is applied to it.
interference-what happens when two waves come together. Interference results in a change in amplitude. If the change is additive (i.e. the amplitudes of the two waves are added) then the interference is constructive. If the opposite occurs, it is destructive interference.
kinetic energy-the energy of a body associated with its motion, defined as k = 1/2mv2.
Law of Electrostatics-states that like charges repel each other, while opposite charges attract each other.
magnetic field-the region in space in which a charge can experience a magnetic force. Magnetic fields flow out of the North Pole and into the South Pole.
magnetism-the property of a charge in motion, caused by the revolution of atoms around the nucleus of an atom. The direction of the magnetic effect is determined by the direction in which the electron spins around its axis.
momentum-the quantity of motion an object possesses, dependent upon the mass of the object and the velocity at which it travels. Thus, p (momentum) = mu. If two objects of unequal size are traveling at the same speed, the object with the greater mass has more momentum. Likewise, if two objects of equal size are traveling at different speeds, then the object with the greater speed has more momentum. Momentum is dependent upon velocity (a vector quantity), and is thus a vector quantity.
period-shortest length of time it takes a periodic motion to repeat.
polarization-the selective passage of waves that only vibrate in a particular plane.
potential energy-energy dependent upon relative position as opposed to motion. Potential energy is caused by gravity or elasticity. Thus, an object's potential energy is dependent upon either its distance from the earth or the degree to which a coiled spring attached to the object has been stretched. Potential energy can be changed into kinetic energy either by dropping the object or releasing the spring.
reflection-the bouncing of a wave off a surface. Reflection of light is responsible for the formation of images in mirrors.
refraction-the bending of light