Question

lete the sentences to explain why scientists were concerned about the use of cfcs. uvc waves break down chlorofluorocarbons in the stratosphere. as the amount of chlorofluorocarbons in the stratosphere increases, the number of ozone molecules will decrease. as a result, more uv waves can pass through the ozone layer and reach earths surface.

Explanation:

Step1: Understand CFC - ozone reaction

CFCs are broken down by UVC in stratosphere. Chlorine atoms released from CFCs react with ozone ($O_3$) molecules. Each chlorine atom can destroy many ozone molecules. So as CFC amount increases, ozone molecules decrease.

Step2: Understand ozone - UV relation

The ozone layer absorbs most of the harmful UV radiation. When the amount of ozone decreases, the ozone layer's ability to block UV radiation is reduced. So more UV waves (especially UVB which can cause skin cancer, cataracts etc.) can pass through and reach Earth's surface.

Answer:

The first blank is "decrease" because CFCs react with ozone and deplete it. The second blank is "more" because with less ozone, less UV is absorbed and more can reach Earth.