Question

1. substances that start a chemical reaction are known as the *

a. reactants
b. products
c. chemicals
d. substances

1. which of the following parts of the experiment is the best example of a chemical change?

a. wrapping the magnesium with the wire
b. inserting the rubber stopper
c. attaching the battery
d. the formation of magnesium oxide

Explanation:

For question 15:

• Reactants are the substances that start a chemical reaction.
• Products are the substances formed as a result of the reaction.
• Chemicals is a general term.
• Substances is also a general term.

For question 24:

• A chemical change results in the formation of new substances.
• Wrapping magnesium with wire, inserting a rubber stopper, and attaching a battery are physical changes (no new substances formed).
• The formation of magnesium oxide (\(MgO\)) from magnesium (\(Mg\)) and oxygen (\(O_2\)) is a chemical change as a new substance (magnesium oxide) is formed.

Answer:

1. A. reactants
2. D. the formation of magnesium oxide