Physical Science Chapter 5

Front 1

name one observable characteristic of a chemical reaction

Back 1

the production of new materials with properties that are differenct from those of the starting materials

Front 2

Name some observable changes in properties

Back 2

state, color, temperature, smell, etc.

Front 3

What is a precipitate?

Back 3

a solid that forms from solutions during a chemical reaction

Front 4

Name a second observable characteristic of a chemical reaction.

Back 4

a change in energy

Front 5

Some reactions ________ energy while others ______ energy

Back 5

absorb, release

Front 6

Chemical reactions occur when chemical bonds _________ or when ______ ________ form.

Back 6

break, new bonds

Front 7

What are the two things that determine the properties of a substance?

Back 7

the types of atoms that are present and the types of chemical bonds they form

Front 8

Define chemical equation.

Back 8

a shorter, easier way to show chemical reactions, using symbols instead of words

Front 9

How do you write a chemical formula?

Back 9

Identify the elements in a compound as well as the ratio of these elements

Front 10

What do subscripts show?

Back 10

the number of atoms of an element in a molecule or the ratio of elements in a compound

Front 11

What does the structure of a chemical equation do?

Back 11

summarizes a reaction. It tells you the substances you start with and the substances you end with.

Front 12

What are reactants?

Back 12

the materials you have at the beginning of the reaction

Front 13

What are products?

Back 13

the materials you have at the end of the reaction

Front 14

What would a basic equation look like?

Back 14

reactant + reactant ->produict + product

Front 15

Explain conservation of mass

Back 15

No matter hw many reactants and products are involved, all the atoms present at the start of a reaction are present at the end. The amount of matter involved in a chemical reaction does not change. During a chemical reaction, matter is not created or destroyed.

Front 16

What does a balanced equation look like?

Back 16

the same number of each type of atom on both sides of the equation

Front 17

What is a coefficient?

Back 17

a number placed in front of a chemical formula in an equation

Front 18

What is synthesis?

Back 18

when two or more substances (elements or compounds) combine to make a more complex substance

Front 19

Explain decomposition.

Back 19

While a synthesis builds compounds from simpler reactants, decomposition breadks down compounds intgo simpler products

Front 20

When does replacement occur?

Back 20

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

Front 21

Chemical reactions need ______ to get started.

Back 21

a certain amount of energy

Front 22

What is Activation Energy?

Back 22

the minimum amount of energy needed to start a chemical reaction

Front 23

Both endothermic and exothermic reactions require _______ to start.

Back 23

energy

Front 24

_____________ reactions do not need additional energy to continue, so they _____ _____ heat.

Back 24

exothermic, give off

Front 25

__________ reactions need additional energy to continue the reaction, so the _______ heat.

Back 25

endothermic, absorb

Front 26

Chemists control the rate of reactions by changing factors such as _______, _______ and ________ and by using substances called ________ and ________.

Back 26

concentration, temperature, and surface area
catalysts and inhibitors

Front 27

What is concentration?

Back 27

the amount of one material in a given amount of another material

Front 28

When you heat a substance, its _________ move faster and _______ the reaction rate in two ways.

Back 28

particles, increase

Front 29

How does the reaction rate increase when a substance is heated?

Back 29

Particles contact each other more often and have more energy

Front 30

How does surface area relate to a chemical reaction?

Back 30

Only the surface particles of a solid can react with a liquid or gas.

Front 31

What happens when you increase the surface area?

Back 31

you increase the amount of the solid that can come in contact with to other reactant

Front 32

What is a catalyst?

Back 32

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

Front 33

What are enzymes?

Back 33

biological catalysts contained in the cells of living things

Front 34

What are inhibitors?

Back 34

maretials used to decrease the rate of a reaction