Science Test Flashcards
Alloy
A mixture of two or more metals. Common alloys are steel, brass and bronze. Gold jewelry is an alloy; the amount of gold in the jewelry is expressed in karats. Each karat is 1/24 gold; hence 24-karat gold is 100%gold.
Anion
A negatively charged ion.
Boiling
A phase change from a liquid to a gas (vapor).
Cation
A positively charged ion.
Chemical Change
A change that results in a new substance with new physical and chemical properties
Combustion
An exothermic chemical reaction; burning.
Compound
A substance composed of two or more different elements chemically combined in a definite ratio. A compound can be decomposed by a chemical change.
Condensation
The change in state of matter from a vapor to a liquid. Condensation of water vapor during cloud formation releases large amounts of energy to the atmosphere.
Covalent bond
A chemical bond formed when atoms share electrons (for example, CO2).
Decomposition
A chemical reaction in which the reactants are broken apart; the chemical breakdown of a substance into simpler substances.
Entropy
A quantitative measure of the disorder of a system. There is a tendency in nature to proceed toward a state of greater disorder. The entropy of the universe is steadily increasing.
Freezing
The change is phase of a substance from a liquid to a solid. The substance releases energy.
Gas
A phase of matter that has no definite shape or volume.
Melting Point
The temperature at which a phase change occurs from solid to liquid; the same as the freezing point. When a solid melts; it absorbs heat energy and changes to the liquid phase. The amount of heat required to accomplish this phase change is called the heat of fusion.
