What are polymers?
...very large molecules

You are probably very familiar with the words like plastic and rubber, and you can likely name many items or materials made with them. In fact the computer has many plastic parts and your shoes likely have some rubber material. Look around you and see what other items are made with plastic or rubber. How many can you see?

Now can you define the words? What is plastic? What is rubber? Before these questions are answered specifically, let's look at the word polymer. Both plastic and rubber are made from polymers. Polymers are macromolecules (very large molecules) that are found everywhere.

Chemically combining a small molecule (or monomer) to itself hundreds to thousands of times produces a polymer. For example the monomer, glucose (a simple sugar), is converted to the polymer, cellulose, by plants. There are many different kinds of polymers. There are natural (cellulose, protein) and synthetic or man made (polyethylene, polystyrene) polymers.

As a result of their large size, polymers can have unusual physical properties. Furthermore variations in the type of elements and bonds in the polymer changes the physical properties. Some polymers can be pliable or "easily" shaped or molded. These are referred to as plastics. Other polymers can return to their original shape after being stretched. These are referred to as rubbers or elastomers. The physical properties of polymers are temperature dependent.

Lets take a look at how heat affects polymers.