Study for the Chemistry Test - 8th grade

a force that holds two or more atoms together

• repulsion

• chemical bond

• gravity

• magnetism

a substance that increases reaction rate by lowering the activation energy of a reaction

• product

• reactant

• catalyst

• precipitate

substances change into new substances with different physical and chemical properties

• chemical change

• physical change

• enzyme

• balancing equations

big number in front of an element symbol or chemical formula in an equation; tells how many molecules; used to balance equations

• atomic number

• atomic mass

• subscript

• coefficient

chemical reaction in which a substance combines with oxygen and releases energy; burning a fuel with oxygen; produces carbon dioxide and water; plus signs on both sides of the arrow

• combustion

• decomposition

• synthesis

• photosynthesis

a type of reaction in which one compound breaks down into two or more simpler substances; plus sign only on the right side of the arrow

• combustion

• synthesis

• photosynthesis

• decomposition

a chemical reaction that absorbs (takes in) energy; feels cooler to the touch

• precipitate

• endothermic

• enzyme

• exothermic

a catalyst that speeds up chemical reactions in living cells; examples are amylase in your saliva, and pepsin in your stomach to speed up reactions to break down the food you eat

• precipitate

• reactant

• enzyme

• product

a chemical reaction that releases energy; can give off energy as heat, or light, or electricity, or sound

• exothermic

• physical change

• endothermic

• enzyme

a change in the size, shape, form, or state of matter that does not change the matter's identity; looks different, but is actually the same substance as before

• endothermic

• exothermic

• physical change

• chemical change