1. The heads-up pennies represent the radioactive atoms, the tails-up pennies represent the stable atoms, and the container could be anything that has radioactive atoms in it the period of shaking represents the half-life.

2. The half-life is the amount of time needed for half of a sample to change. An unstable isotope that will break down. A stable isotope is one that will not change.
3.
Uranium 238 4.5 * 1010 Uranium is used to produce energy in the form of electricity
Carbon 14 5.7 * 103 Carbon 14 is used for dating organic material
Potassium 40 1.3 * 109 Potassium 40 can be used for radioactive dating

4. The process of radioactivity releases energy because when you change the mass of an atom energy is released. (E=mc2)

5. Four ways radioactivity can be used beneficially are for electric power, tracers and geological dating. Four harmful things are sickness, the atom bomb and the hydrogen bomb.

Regents Questions

1. After a certain number of years, the Rubidium 87 has decayed the least because it has the longest half-life.

2. Carbon 14 would be the most useful for finding the approximate age of a late Pleistocene campfire because the wood burning in the fire contains carbon.

3. The rock containing Potassium minerals is 650,000,000 years old if 75% is gone. Therefor, 75% is half of the half-life and half of 1.3 billion years is 650,000,000 years.

4. After 5 half-lives, there would be 3.13% of Carbon 14 left or 1/32 left. The sample containing this would be 30,000 years old.

Half-Lives Percent Left Fraction Left Parent; Daughter Ratio C14
‘Age” * 103

Start 100% 1 - 0
1 50% 1/2 1:1 6
2 25% 1/4 1:3 12
3 12.5% 1/8 1:7 18
4 6.25% 1/16 1:15 24
5 3.13% 1/32 1:31 30
6 1.56% 1/64 1:63 36
7 0.78% 1/128 1:127 42
8 0.39% 1/256 1:256 48

5. In the diagram substance “N” has the longest half-life because it took the longest time of all the other substances to split into halves.