Visionneuse

Date_TXT

New-York : Glencoe/Mcgraw-Hill, sd.

Auteur

Glencoe

Sujet

Chemistry ; Atoms; Solving chemistry ; Chemistry Handbook

Type de document

Livre

Description :

A chemical is any substance that has a definite composition. Ozone is a chemical that is made up of three particles of oxygen. Ozone
forms a thick blanket above the clouds in the stratosphere. This layer of ozone protects Earth from overexposure to ultraviolet radiation
from the Sun. You are probably familiar with the damage that exposure to ultraviolet radiation can do to your skin in the form of
sunburn. Ultraviolet radiation can also harm other animals and plants. In the 1980s, scientists documented that the ozone layer
around Earth was becoming measurably thinner in some spots. In the 1970s, scientists had observed that large quantities of
chlorofluorocarbons (CFCs) had accumulated in Earth’s atmosphere. CFCs are chemicals that contain chlorine, fluorine, and carbon.
CFCs were used as coolants in refrigerators and air conditioners and as propellants in spray cans because they were considered relatively
nonreactive. Some scientists hypothesized that there might be a connection between the concentration of CFCs in the atmosphere and
the thinning of the ozone layer.