PhySci Finals Study Guide
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58 terms
Terms | Definitions |
|---|---|
 reactant | a substance or molecule that participates in a chemical reaction. |
| product | a substance that forms in a chemical reaction. |
| chemical energy | the energy released when a chemical compound reacts to produce new compounds. |
| exothermic reaction | a chemical reaction in which energy is released to the surroundings as heat. |
| endothermic reaction | A chemical reaction that requires energy input. |
| chemical equation | a representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products. |
| mole ratio | the relative number of moles of the substances required to produce a given amount of product in a chemical reaction. |
| synthesis reaction | a reaction in which two or more substances combine to form a single compound. |
| decomposition reaction | a reaction in which a single compound breaks down to form two or more simpler substances. |
| combustion reaction | the oxidation reaction of an organic compound, in which heat is released. |
| single-displacement reaction | a reaction in which one element or radical takes the place of another element or radical in a compound. |
| double-displacement reaction | a reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds. |
| free radical | an atom or a group of atoms that has one unpaired electron. |
| oxidation-reduction reaction | any chemical change in which one species is oxidized (loses electrons) and another species is reduced (gains electrons); also called redox reaction. |
| catalyst | a substance that changes the rate of a chemical reaction without being consumed or changed significantly. |
| enzyme | a molecule, either protein or RNA, that acts as a catalyst in biochemical reactions. |
| substrate | the reactant in reactions catalyzed by enzymes. |
| chemical equilibrium | a state of balance in which the rate of a forward reaction equals the rate of the reverse reaction and the concentrations of products and reactants remain unchanged. |
| suspension | a mixture in which particles of a material are more or less evenly dispersed throughout a liquid or gas. |
| colloid | a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions and that are suspended in a liquid, solid, or gas. |
| emulsion | any mixture of two or more immiscible liquids in which one liquid is dispersed in the other |
| solution | a homogeneous mixture throughout which two or more substances are uniformly dispersed. |
| solute | in a solution, the substance that dissolves in the solvent. |
| solvent | in a solution, the substance in which the solute dissolves. |
| polar | describes a molecule in which the positive and negative charges are separated. |
| hydrogen bond | The intermolecular force occurring when a hydrogen atom that is bonded to a highly electronegative atom of one molecule is attracted to two unshared electrons of another molecule. |
| nonpolar | describes a molecule in which the centers of positive and negative charges are not separated. |
| solubility | the ability of one substance to dissolve in another at a given temperature and pressure. |
| concentration | the amount of a particular substance in a given quantity of a mixture, solution, or ore. |
| saturated solution | a solution that cannot dissolve any more solute under the given conditions. |
| unsaturated solution | a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute. |
| supersaturated solution | a mixture that has more dissolved solute than is predicted by its solubility at a given temperature. |
| molarity | a concentration unit of a solution expressed as moles of solute dissolved per liter of solution. |
| acid | any compound that increases the number of hydronium ions when dissolved in water. |
| indicator | a compound that can reversibly change color depending on conditions such as pH. |
| electrolyte | a substance that dissolves in water to give a solution that conducts an electric current. |
| base | any compound that increases the number of hydroxide ions when dissolved in water. |
| pH | a value that is used to express the acidity or basicity (alkalinity) of a system; each whole number on the scale indicates a tenfold change in acidity. |
| neutralization reaction | the reaction of the ions that characterize acids and the ions that characterize bases to form water molecules and a salt. |
| salt | an ionic compound that forms when a metal atom or a positive radical replaces the hydrogen of an acid. |
| soap | a substance that is used as a cleaner and that dissolves in water. |
| detergent | a water-soluble cleaner that can emulsify dirt and oil. |
| disinfectant | a chemical substance that kills harmful bacteria or viruses. |
| bleach | a chemical compound used to whiten or make lighter, such as hydrogen peroxide or sodium hypochlorite. |
| antacid | a weak base that neutralizes stomach acid. |
| radioactive decay | the disintegration of an unstable atomic nucleus into one or more different nuclides. |
| nuclear radiation | the particles and energy produced during radioactive decay. |
| alpha particle | a positively charged particle that consists of two protons and two neutrons and that is emitted from a nucleus during radioative decay. |
| beta particle | an electron or positron that is emitted from a nucleus during radioactive decay. |
| gamma ray | the high-energy photon emitted by a nucleus during fission and radioactive decay. |
| half-life | the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope. |
| fission | the process by which a nucleus splits into two or more fragments and releases neutrons and energy. |
| nuclear chain reaction | a continuous series of nuclear fission reactions. |
| critical mass | the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction. |
| fusion | the process in which light nuclei combine at extremely high temperatures, forming heavier nuclei and releasing energy. |
| background radiation | the nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air. |
| rem | the quantity of ionizing radiation that does as much damage to human tissue as is done by 1 roentgen of high-voltage X rays. |
| radioactive tracer | a radioactive material that is added to a substance so that its distribution can be detected later. |
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