Matter is something that occupies space (volume) and has weight (mass). There are three states of matter: solid, liquid and gas. A solid has a certain size and shape. A liquid has a size or volume. That means it takes up space, but it conforms to the container so it has no definite shape. Gases have no size or shape of their own.

Matter can be classified as a mixture or a pure substance. A mixture has two or more kinds of particles and may, therefore, have different properties in different samples. A pure substance has the same properties in any sample you choose.

Physical change is a change in matter where no new substance is produced. Chemical change is a change in matter that produces a new substance. Some clues that a chemical change has taken place include a change in the smell or the color of the matter. Sometimes a gas is formed. Chemical changes cannot be reversed without extraordinary means — if at all.

Example:

• Water can change from ice (solid) to water (liquid) to steam (gas). This is a physical change because it can be reversed.

• Take that same water. Mix it with ingredients and bake a cake. This is a chemical change because it would take extraordinary means to separate the ingredients into the form they held before the cake was baked.

 

Web Resources

Thall’s History of Gas Laws
http://web.fccj.org/~ethall/gaslaw/gaslaw.htm

Gases and Their Behavior
http://www.geociies.com/chemisryvillage/gases

Laws of Science
http://www.pbs4549.org/floating/foascienc,htm

Gas Laws
http://www.pbs4549.org/blimp/GAS.HTM