Strand I: Chemistry Unit II: Polymers Teacher/Class Notes
Teacher/Class Notes
Organic vs. Inorganic Organic is made from material from a once living thing. Living things, when decayed, become mostly carbon (along with gases) Molecular Weight Molecular weight: The weight of a molecule is the sum of the weights of the atoms of which it is made. Molecular weight of H2O: 2 H: 1x2 = 2 1O: 1x16 = 16 Total molecular weight: 18 Molecular weight of sugar: C12H22O11 12C: 12x12=144 22H: 22x1=22 11O: 16x11=176 Total molecular weight: 342
Introduce the bars with ionic bonding.
Wilson, Geophysical Science 1
Strand I: Chemistry Unit II: Polymers Teacher/Class Notes
Polymers
Chain demo. What do you think a polymer is if it is a lot like the chain? Small molecules (monomers) linked together to form one long polymer chain. Ex: Ethylene to Polyethylene Initiator breaks the weaker of the double bonds. The lone electron breaks the next weaker of the double bonds and off it goes.
Wilson, Geophysical Science 2
Strand I: Chemistry Unit II: Polymers Teacher/Class Notes
Only a few elements can make a polymer:
Element
Hydrogen, H
# valence electrons
# bonds allowed
1 7 6 5 4
1 1 2 3 4
Chlorine, Cl
Oxygen, O
Nitrogen, N
Carbon, C
Hand holding: Remember how many bonds carbon has.
1. Have students make electrons on paper and then everyone sticks 2 electrons on their shoulders and sticks the other 2 on each hand. 2. Bond together as a class. 3. Break the weaker double bond 4. Bond those 2 electrons. Natural polymers are things like tar, tortoise shell, horns
Properties of Polymers:
Entanglement:
Totally depends on molecular weight. The higher the weight the longer the chain and the more it will entangle.
Relaxation:
Silly putty: when you pull slowly the chains slowly become untangled. When you pull fast the silly putty will snap apart. Bullet-proof vest: slowly a knife can go through. Fast bullet cannot go through. Heat can speed up relaxation (adds energy, increase vibration, vibrates chain apart.)
Crosslinking:
Need a crosslinking agent. Ex: Epoxy comes in two bottles. The glue and the crosslinking agent. Crosslinked polymers cannot melt…that’s how strong the bonds are. They just burn.
Wilson, Geophysical Science 3
Strand I: Chemistry Unit II: Polymers Teacher/Class Notes
Crosslinked polymers are stiff and brittle. (epoxy-crosslinked, polyethylene-entangled)
Linear and Branched Polymers:
Linear: High Density – (milk jugs) More linear formation so the polymer chains can come closer together…more rigid material. Branched: Low Density (sandwich baggies)– Chains can’t get close so the material is more flexible and light can pass through.
What can affect a plastic?
Color (clear or not) Heat (crosslinked/entangled)… Temperature will increase the vibrations and vibrate the chain apart. Density (different polymers have different densities…float) Flexibility (linear/branched, crosslinked/entangled) Tearability (candy bag…inter and intramolecular forces)
Examples of Polymers
C2H4 = ethylene (gas) C4H10 = butane (border of liquid and gas) C5H12 = pentane (liquid) The larger the molecular weight and chain, the more solid it becomes. Water vs. Polyacrylimide with magnetic stirrer…What’s happening?? Could be used as a pop quiz.
Types of Plastics and Recycling Weston recycles #1 & #2 plastics only. 1. PETE: Polyethylene Terephthalate. Commonly used for beverage containers,
Wilson, Geophysical Science 4
Strand I: Chemistry Unit II: Polymers Teacher/Class Notes
boil-n pouches, and processed meat packages.
2. HDPE: High-Density Polyethylene. Commonly used for milk and water bottles, detergent bottles, and toys.
3. PVC: Poly Vinyl Chloride. Commonly used for food wraps, surgical gloves, and piping blister packaging.
4. LDPE: Low-Density Polyethylene. Commonly used for shrink-wrap film, bag films, and garment bags.
5. PP: Polypropylene. Commonly used for margarine and yogurt containers, caps for containers, medicine bottles, and car seats.
6. PS: Polystyrene. Commonly used for disposable plastic silverware, egg cartons, fast food packaging, video cassettes, and televisions.
7. Other: Commonly used for multi-resin containers.
Wilson, Geophysical Science 5