AFOQT Study Guide Flashcards
Absolute Zero
The lowest possible temperature (-273.15 C)
Atmospheric Pressure
The pressure exerted by the gases in the air. Units of measurement are kilo-pascals (kPa), atmospheres (atm), millimeters of mercury (mm Hg), and Torr. Standard atmospheric pressure is 100 kPa, 1atm, 760 mm Hg or 760 Torr.
Atom
The smallest particle of an element, a nucleus and its surrounding electrons.
Atomic Mass
The mass of an atom measured in atomic mass units (amu). An atomic mass unit is equal to one-twelfth of cardon-12. Atomic mass is now more generally used instead of atomic weight. Example: the atomic mass of chlorine is 35 amu.
Atomic Number
Also known as proton number, it is the number of electrons or the number of protons in an atom. Example: the atomic number of gold is 79
Atomic Weight
A common term used to mean the average molar mass if an element. This is the mass per mole of atoms. Example: the atomic weight of chlorine is about 35 g/mol.
Boiling Point
The temperature at which a substance undergoes a phase from liquid to a gas.
Celsius Scale (C)
A temperature scale on which the freezing point of water is 0 degrees and the normal boiling point at standard atmospheric pressure is 100 degrees.
Change of State
A change between two of the three states of matter, solid, liquid, and gas. Example: when water evaporates it changes from a liquid to a gaseous state.
Compound
A chemical consisting of two or more elements chemically bonded together. Example: Calcium can combine with carbon and oxygen to make calcium carbonate (CaCO3), a compound of all three elements.
Condensation
The formation of a liquid from a gas. This is a change of state, also called a phase change.
Conduction
(i) the exchange of heat (heat conduction) by contact with another object, or (ii) allowing the flow of electrons (electrical conduction).
Convection
The exchange of heat energy with the surroundings produced by the flow of a fluid due to being heated or cooled.
Decay (radioactive decay)
The way that a radioactive element changes into another element due to loss of mass through radiation. Example: uranium 238 decays with the loss of an alpha particle to form thorium 234.
Density
The mass per unit volume (e.g. g/cm3)
Diffusion
The slow mixing of one substance with another until the two substances are evenly mixed. Mixing occurs because of differences in concentration within the mixture. Diffusion works rapidly with gases, very slowly with liquids.
Dissolve
To break down a substance in a solution without causing a reaction.
Electrical potential
The energy produced by an electrochemical cell and measured by the voltage or electromotive force (emf).
Electron
A tiny, negatively charged particle that is part of an atom. The flow of electrons through a solid material such as wire produces an electric current.
Element
A substance that cannot be decomposed into a simpler substance by chemical means. Examples: calcium, iron, gold.
Explosive
A substance which, when a shock is applied to it, decomposes very rapidly, releasing a very large amount of heat and creating a large volume of gases as a shock wave.