68 BASIC CHEMISTRY TERMS WITH DEFINITIONS

Chemistry Vocabulary

Substance A type of matter with a fixed composition.

Element An element is chemically the simplest substances and hence cannot be broken down using chemical reactions.

Compound A substance in which the atoms of 2 or more elements are combined.

Heterogeneous Mixture A mixture in which different materials can easily be distinguished.

Homogeneous Mixture Contains 2 or more gases, liquids, or solids substances blended evenly.

Solution Homogeneous mixture with particles so small that they cannot be seen with a microscope.

Colloid Type of mixture with particles that are larger than those in solutions, but not heavy enough to settle out.

Tyndall Effect Scattering of light by colloidal particles.

Suspension A heterogeneous mixture containing a liquid where visible particles settle.

Physical Property Characteristic of a material you can observe without changing the identity.

Physical Change A change in size, shape, or state.

Distillation A process for separating substances by evaporating a liquid and recondensing its vapor.

Chemical Property Characteristic of a substance that indicates whether it can undergo a chemical change.

Chemical Change A change of one substance to another.

Law of Conservation and Mass The mass of all substances that are present before a chemical change equals the mass of all the substances after the change.

Kinetic Theory Explanation of how particles in matter behave.

Melting Point The point in temperature when the solid starts to liquefy.

Heat of Fusion The energy required to change a substance from a solid to a liquid at its melting point.

Boiling Point The point in temperature when the liquid starts to boil.

Heat of Vaporization Amount of energy required for a liquid to become a gas.

Diffusion Spreading of particles throughout a given volume until they are distributed.

Buoyancy The ability of a fluid to exert an upward force on an object immersed in it.

Pressure Force exerted per area.

Viscosity The resistance to flow by a fluid.

Pascal Used to measure pressure.

Atom An atom is the smallest unit of matter that has the properties of an element.

Nucleus The center of an atom.

Protons Particles in an atom with a positive charge.

Neutrons Particles in an atom with no charge.

Electrons Particles in an atom with a negative charge.

Quarks Smaller particles in neutrons and protons.

Electron Cloud The area around a nucleus where electrons are mostly found.


Atomic Number The number of protons found in the nucleus of an atom.


Mass Number This number is the sum of the number of protons and neutrons.


Isotopes Atoms of the same element that have different numbers of neutrons.


Average Atomic Mass Is the weighted average mass of its isotopes.


Periodic Table A table filled with elements in order of atomic numbers, etc.


Groups The vertical columns in the periodic table.


Electron Dot Diagram Uses the symbol of the element and dots to represent electrons.


Periods Horizontal rows of elements.


Metals Good conductors of heat and electricity.


Malleable Can be hammered.


Ductile Flexible.


Metallic Bonding Positively charged metallic ions surrounded by an electron cloud.


Transitional Elements Between groups 1 and 2, and 13 and 18.


Nonmetals Usually gasses or brittle solids at room temperature.

Diatomic Molecule Consists of 2 atoms of the same element in a covalent compound.

Sublimation The process of a solid going directly into a vapor.

Metalloids Has properties of both nonmetals and metals.

Allotropes Different forms of the same element

Semiconductors Elements that conduct under circumstances.


Chemical Formula A formula that shows what elements are in a compound and what it will become.


Chemical Bond The force that holds atoms together in a compound.


Ionic Bond Force of attraction between opposite charges.

Covalent Bond Attraction formed when elements share electrons.

Molecule A neutral molecule that forms as a result of electron sharing.

Binary Compound Composed of two elements.

Oxidation Number Tells you how many electrons an atom has gained or lost.

Polyatomic Ion Positively or negatively charged, covalently bonded group.

Chemical Reaction More than one substances turning into other substances.


Reactants Substances that react.


Products Substances that are made.


Coefficients Numbers in front of each substance in an equation.


Combustion Reaction Substance reacts with oxygen to make heat and light.


Synthesis Reaction 2 or more substances that combine to make another.


Decomposition Reaction One substance breaks down, into 2 more.


Single Displacement Reaction One element replaces another to make a product.


Double Displacement Reaction Two elements replace another to make a product.