Question

which two parts of the activity indicate a chemical reaction occurs when the calcium oxide mixes with water?
a calcium oxide mixes with water
b the temperature of the water increases.
c a substance can be separated from the water after mixing.
d the separated substance is a white powder.
e the separated substance has a different density than calcium oxide

Explanation:

• Option B: An increase in temperature (exothermic reaction) is a sign of a chemical reaction. When calcium oxide reacts with water (\(CaO + H_2O=Ca(OH)_2\)), heat is released.
• Option E: A change in density indicates a change in the nature of the substance. Since density is a characteristic property of a substance, a different density implies a new substance is formed (a chemical reaction).

Answer:

B. The temperature of the water increases; E. The separated substance has a different density than calcium oxide.