Ch. 5 Physical Science Test

The only sure evidence for a chemical reaction is

• the formation of a gas.

• a color change

• the production of one or more

• changes in properties

A material used to decrease the rate of a chemical reaction is a(n)

• inhibitor

• catalyst

• enzyme

• fuel

A material used to decrease the rate of a chemical reaction is a(n)

• symbol

• formula

• subscript

• reaction

Which is the correct chemical equation for the following statement?

Sodium reacts with oxygen in a 2 to 1 ratio to produce sodium oxide.

• 4 Na + O₂ 2 yields Na₂O

• 2 Na + O₂ yields 2 NaO

• Na₂O + O₂ yields 2 NaO

• Na₂ + O₂ yields Na₂O₂

The principle of conservation of mass is true

• only for reactions that take place in open systems.

• only for reactions that take place in closed systems.

• for reactions in both open and closed systems.

• for no reactions at all.

In chemical reactions, what does the principle of conservation of mass mean?

• Matter is not created or destroyed.

• The total mass of the reactants is greater than the total mass of the products.

• The total mass of the reactants is less than the total mass of the products.

• Matter is not changed.

Chemicals that act as biological catalysts by speeding up reactions in living things are called

• inhibitors

• enzymes

• fuels

• reactants

Which of the following is an example of how to supply activation energy to begin a reaction?

• Cool the reaction flask in an ice bath

• Add a catalyst

• Heat the reaction flask

• Add an inhibitor

A bottle of hydrogen peroxide that eventually turns into a bottle of water and oxygen gas is an example of a

• synthesis reaction

• decomposition reaction

• replacement reaction

• precipitate reaction

Physical changes occur when existing bonds break and new bonds form.

• True

• False