Question

the first reaction bubbled because a ______ was formed.
a gas
b liquid
c solid
the yellow color seen in the second reaction was due to the presence of a solid known as a ______.
a substrate
b precipitate
changes in color and temperature indicate that a ______ reaction has taken place.
a chemical
b physical

Explanation:

1. Bubbling in a reaction is often due to the formation of gas.
2. A solid formed in a solution - phase reaction is called a precipitate, which can cause color changes.
3. Changes in color and temperature are characteristic signs of a chemical reaction, as they indicate the formation of new substances with different properties.

Answer:

1. A. gas
2. B. precipitate
3. A. chemical