Poly- means "many and mer means "part" or "segment". Polymers are assembled of many molecules connected to form really longs chains. What makes polymers interesting is that how they act depends on what kinds of molecules they're made up of and how they are put together. The properties of anything made out of polymers really reflect what is going on at the molecular level. Things that are made of polymers look, feel, and act depending on how their atoms and molecules are connected, as well as which ones we use to begin with. Some can be rubbery, like a bouncy ball, some are sticky and gooey, and some are hard and tough, like a skateboard.
How much is a lot? A single polymer molecule is made out of hundreds of thousands (or even millions) of monomers. The special name of "monomer" because not all molecules can form polymers. An example of a working polymer is ethylene because it is a monomer and it can hook up with others like itself to make a polymer. Sometimes polymers are called "macromolecules".
Types of polymers are: linear, branch. A linear polymer is made up of one molecule after another, linked together in a long chain. Linear polymers don't have to be in a straight line. Single bonds between atoms in the chain can swivel around a bit, kind of like paper clips hooked together end-to-end. A linear polymer chain starts at the beginning and goes straight to the end. "Linear" means "straight and not curved," but for polymers, linear means "straight and not branched." A branched polymer chain has extra branches.
Atoms that make up the backbone of a polymer chain come in a regular order and the order repeats itself along the length of the polymer chain. Its backbone chain is made up of just two atoms repeated over and over again. Polymers don't start out big; they start as tiny little molecules.
Remember, the chains of polymers:
can stick, twist, and get tangled up.
can stick together.
move much slower because they're so big.
The longer the chain, the more tangled up it can get. Since the chains are harder to pull out or separate. That makes polymers stronger. Some polymers are more straight and stiff than others. They won't get tangled up as much but they're strong for a different reason stiff chains can pack together and stick to each other.
Molecules can be pulled apart easily, but others take a lot more energy to pull them apart. Polymers are the same way. When the chains stick together very strongly, it can be really tough to pull them apart. If the chains happen to be straight, stiff, and all lined up next to each other, it can really be hard to pull them apart.
When polymers dissolve in a liquid, the long chains move around so slowly that they make the solution flow much slower. The longer the chains, the slower the flow.