EVIDENCES OF CHEMICAL REACTIONS

If two substances react and the temperature of the mixture increases, the reaction is ____

• Endothermic

• Not one that produces anything new

• One that needs a catalyst

• Exothermic

In a chemical reaction, if the reactants are heated, the reaction usually happens

• faster

• slower

• at the same rate

• in a smaller volume

Which of the following is NOT a true statement concerning what happens in all chemical reactions?

• The ways in which atoms are joined together are changed.

• New atoms are formed as products.

• The starting materials are named reactants.

• The bonds of the reactants are broken and new bonds of the products are formed.

One clue of a chemical change is the formation of a precipitate. A precipitate is formed when___

• Two liquids react and a gas is produced

• A solid dissolves in a liquid

• One liquid dissolves in another

• Two liquids react and a solid is formed

According to the law of conservation of mass, the total mass of the reacting substances is

•  always more than the total mass of the products

• always less than the total mass of the products

• sometimes more and sometimes less than the total mass of the products

• always equal to the total mass of the products.

A substance that enters into a chemical reaction is called a

• mole

• product

• reactant

• coefficient

In a chemical equation, the symbol that takes the place of the word yields is a(n)

• equal sign

• coefficient

• plus sign

• arrow

Which of the following symbols means a substance is in water solution?

• (aq)

• (s)

• (w)

• (l)

Which observation does NOT indicate that a chemical reaction has occurred?

• formation of a precipitate

• production of a gas

• evolution of heat and light

• change in total mass of substances

A solid produced by a chemical reaction in solution that separates from the solution is called

• a precipitate.

• a reactant

• a molecule

• the mass of the product