Chapter 8Sections 2 and 3

Chapter 4 Section 5

• Monomers- smaller molecules that join together to make polymers

Natural Polymers• found in nature, ex. Cellulose (cell walls),

starch (plant sugar), glycogen (animal sugar), silk, wool, proteins

SyntheticPolymers

• man made, not natural, ex. plastics, nylon, polyester, laminate flooring, teflon, CDs

• Sometimes the polymer chains get up to 500,000 carbons long. Here they are tough enough for synthetic ice, replacement joints and bullet-proof vests. This is called Ultra High Molecular Weight PolyEthylene or UHMWPE.     Think about it. You start with ethylene gas molecules that can't stop a feather from passing through them. But after the double-bond of one ethylene molecule breaks, it causes a chain reaction that connects thousands to it. In less than a second, these long straight chains of carbon and hydrogen aligned next to each other are strong enough to stop a bullet or play ice hockey on. Isn't chemistry wonderful?

Composite

• Combining two or more polymers, each with specific useful properties, into one new substance that is better than either polymer was individually

• Examples– Natural- wood– Synthetic- fiberglass, kevlar

Nuclear Reactions

• Radioactive decay- when the nucleus in an unstable isotope releases fast moving particles and energy

• Types: alpha (α), beta (β), gamma (γ)

Alpha Radiation α– nucleus loses 2 protons,

2 neutrons and energy (sometimes called a Helium nucleus)

– decreases the atomic mass of the element by 4

– decreases the atomic number by 2 (element changes new element)

– protection requires thin material like paper

Beta Radiation β– nucleus loses 1 neutron

and energy, the neutron breaks into a proton and an electron, only the proton remains in the nucleus

– the atomic mass of the element doesn’t change

– increases the atomic number by 1 (element changes new element)

– protection requires thin layer of plastic or metal like aluminum foil

Gamma Radiation γ

– gives off extremely high amounts of energy– protection requires a meter of concrete or 6

inches of lead

Half-Life

• length of time needed for half the atoms of a sample to decay

• example- original sample has 32 grams of carbon-14 (half-life is 5,730 years)

• after 1 half-life, only 16 grams of carbon-14 remain• after 2 half-lives, only 8 grams of carbon-14 remain• after 3 half-lives only 4 grams of carbon-14 remain• the time needed for the sample to decay from 32 g

to 4 g is 5,730 x 3 = 17,190 years.