Ch 7 Vocabulary-physical science

Name: _Ms. Long__________________________________________ Date: _______________ Period: __________________

Chapter 7 Vocabulary (PS)





Activation Energy



minimum amount of energy

The minimum amount of energy needed to start a chemical reaction





increases the rate

A material that increases the rate of a reaction by lowering the activation energy


Chemical change



form new substances

A change in which one or more substances combine or break apart to form new substances


Chemical equation


using symbols

A short, easy way to show chemical reactions, using symbols


Closed system



which no matter is allowed to enter

A system in which no matter is allowed to enter or leave





A number in front

A number in front of a chemical equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction





certain volume

The amount of one material in a certain volume of another material





breaks down

A chemical reaction that breaks down compounds into simple products


Endothermic reaction



A reaction that absorbs energy






1. a type of protein that speeds up a chemical reaction in a living thing

2. a biological catalyst that lowers the activation energy of reactions in cells




Exothermic reaction




Release energy



A reaction that releases energy, usually in the form of heat





Decreases rate

A material that decreases the rate of a reaction


Law of conservation of Mass


Not created or destroyed

The principal that the total amount of matter is neither created or destroyed during any physical or chemical change


Open system



matter can enter from or escape

A system in which matter can enter from or escape to the surroundings


Physical Change



does not make

A change that alters the form or appearance of a material but does not make the material into another substance.





forms from a solution during

A solid that forms from a solution during a chemical reaction






A substance formed as a result of a chemical reaction






A substance that enters into a chemical reaction





trade places

A reaction in which one element replaces another in a compound or when two elements in different compounds trade places





a new, more complex substance

A chemical reaction in which two or more simple substances combine to form a new, more complex substance