MOLECULES AND POLYMERS
Here's the million-dollar question of the day: What are polymers?
Hmm…Not sure?
First you need to know what a molecule is. A molecule is the smallest part of
something that is still that thing. "Huh?" you ask. Well, what's water? Besides
wet, it's also known as H2O. H2O is a molecule-a water molecule made up of two
hydrogen atoms and one oxygen atom. The glass of water you drink when you
come in from playing outsides is just millions of H2O molecules floating around in
your glass.
"So what's a polymer?" Here's a quick Latin lesson: "Poly" means many and "mer"
mean units or parts. So a polymer means…. You got it! It's a large molecule made
up of many repeating parts or subunits. Water is not a
polymer because it only has H2O.
POLYMERS EVERYWHERE
"Why do people care so much about polymers?" Polymers are everywhere. The
plastic casing of your computer is made of polymers. In fact, all plastics are
polymers! Where would you be without plastics! Good question. Look around
your house and see if you can find a room without plastics in it!
Now, not all polymers are plastics. Got that? All plastics are
polymers but not all polymers are plastics. You know those
gummy bears you had in your lunch today…they are polymers.
So is the milk in your cereal, the cheese in your sandwich, the
muscles in your arms and legs, and the DNA that makes up who
you are! The pantyhose your mom makes you wear on special
occasions are made of nylon-another polymer. The silk in your
best Sunday dress is also a polymer.
Polymers are very important in the world of bioengineering and the medical
sciences. People who have lost an arm or leg in an accident get special parts made
for them so they can live normal lives.
Much of the equipment used by police officers, fire fighters, and even astronauts
is also made of polymers.
WHAT'S HAPPENING?
Have you ever seen a chemical reaction? Even if you didn't know it, you see it
hundreds of times. You saw one when you made your slime. A chemical reaction
changes 2 or more substances into a new substance. Have you ever baked a cake?
You start off with some eggs, flour, and sugar. Then you bake it and you have
fluffy cake! That's an example of a chemical reaction.
Chemical reactions can be either make or take in heat. Reactions that produce
heat are called exothermic. Burning is an exothermic reaction. The other type of
reaction absorbs or takes in heat from its surroundings and is called endothermic.
Can you guess which type of reaction produces the slime you made? How did the
slime feel when you made it? It should have felt cold. As you knead the slime and
handle it, it absorbs heat from your hands. Do you know what kind of reaction it is
yet? You guessed it! It's endothermic.
We already talked about polymers. Remember that a polymer is a large molecule
made up of many repeating subunits. You might be wondering if polymers have
chemical formulas like water - H2O. They don't have definite chemical formulas
because the chains that are formed all have different lengths.
How
can
you
tell
Polymers
apart?
Unless you have super microscopic vision, you probably can't see the molecules
that make up different substances. So how do you know it's a
polymer?
If we're talking about food there are two things you want to look
for: Protein and stretchiness. Protein is the easy one…you can
just look on the nutrients label. Stretchiness is another story.
Some stretchy foods include: gum, gummy bears, and twizzlers.
If you're not talking about food how can you tell if something is a polymer? If you
look around the house at different things you'll find polymers
in
plastics and rubber objects. Remember every plastic is a
polymer!
What did you notice about the Silly Plubber you made? Does it
flow like water? Or does it flow very slowly? One property of
polymers is that they are highly viscous. Viscosity is a fluid's resistance to flow.
"Huh?" you ask again. Well, water likes to flow very fast. Just turn on the faucet in
your sink and you can see that. But not all liquids are in such a hurry to get
somewhere. Have you ever put maple syrup on your pancakes? Does maple syrup
come out as fast as water? No. And we say that maple syrup is more viscous than
water. Well, polymers like our slime tend to be more viscous. In fact, talking
about maple syrup, it is a polymer too! So next time you have maple syrup with
your breakfast, tell your little brother he's eating polymers!
1) What is a polymer?
2) Give 5 examples of polymers…
3) All plastics are polymers.
TRUE
FALSE
4) What is the difference between an endothermic and exothermic reaction?
When we make slime, is it endo or exo thermic?
5) What characteristics help you identify a polymer is a polymer? Name at
least 2.
6) What is viscosity? How does this RELATE to polymers? Do polymers have
viscosity?