Carbon Chemistry and Radioactivity Chapter 8 Sections 2 and 3 Chapter 4 Section 5
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.