The Stories of Two Chemicals
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.
Chemistry and Matter.
Chemistry is the study of matter and the changes that it undergoes. Matter is anything that has mass and takes up space. Mass is a measurement of the amount of matter in an object. Everything, however, is not made of matter. For example, heat, light, radio waves, and magnetic fields are some things that are not made of matter.
You might wonder why scientists measure matter in terms of mass, and not in terms of weight. Your body is made of matter, and you probably weigh yourself in pounds.
However, your weight is not just a measure of the amount of matter in your body. Your weight also includes the effect of Earth’s gravitational pull on your body. This force is not the same everywhere on Earth.
Scientists use
mass to measure matter instead of weight because they need to compare measurements taken in different locations.
