15 terms

7th Grade Science: Classes of Matter

Vocabulary list for the 7th grade chemical experimental design module
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molecule
a pure substance made up of two or more atoms which are combined in a constant ratio and held together by chemical bonds. The substance may have two of the same type of atoms (elements) or two different types of atoms (compounds).
substance
A single kind of matter that is pure and has a specific set of properties
element
a pure substance made up of only one type of atom; it cannot be broken down into simpler substances
compound
a pure substance that contains atoms of two or more different kind of elements combined in a fixed ratio.
mixture
A combination of two or more substances (can be atoms, molecules, ions, isotopes, etc.) that are not chemically combined
physical change
A process in which some properties of a substance change, but atoms are NOT rearranged and no new substances are formed.
boiling point
The temperature at which a liquid changes to a gas
conductivity
A material's ability to allow heat or electric charges to flow.
solid
Particles arranged such that their shape and volume are relatively stable. The particles are packed closely together in stable positions.
liquid
Particles that are in constant contact but move freely among themselves. The particles can rearrange to take the shape of their container, but the total volume remains constant.
gas
Particles that are not connected to one another and move freely in all directions. The particles separate in all directions, expanding to fill their container changing both shape and volume.
plasma
Gas particles in which the electrons have been removed from their atoms resulting in an electrically neutral "soup" of both positive and negative particles. Examples are neon signs and lightning
Density
A measure of how much mass is contained in a given volume
coefficient
A number placed in front of a chemical formula in an equation that shows how many copies of the molecule there are
subscript
a number that tells how many atoms of each element are in a molecule
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