1. SPS3 Students will distinguish the characteristics and components of radioactivity.

2. Warm-up: review: strong force vs. electric force unstable nuclei nuclear decay nuclear decay problems 3 types of radiation Fission vs. fusion Half life problems

3. Calculating Half-Life Problems An isotope of cesium (cesium-137) has a half-life of 30 years. If 1.0 gram of cesium-137 disintegrates over a period of 90 years, how many grams of cesium-137 would remain? TimeMass 0 1.0 30.50 60.25 90.125

4. 2. Actinium-226 has a half-life of 29 hours. If 100 mg of actinium-226 disintegrates over a period of 58 hours, how many mg of actinium-226 will remain? mass time 0 100 mg 29 hours 50 mg 58 hours __ mg

5. Nuclear fission is the process of splitting a nucleus Into several smaller nuclei. Only large nuclei, such as the nuclei of uranium and plutonium atoms can undergo nuclear fission. The products of a fission reaction usually include several individual neutrons in addition to the smaller nuclei. The total mass of the products is slightly less than the mass of the original nucleus. Some of the original mass is converted to energy!!

7. Chain Reactions: requires more neutrons each successive generation.

8. Critical mass – is the amount of material required so that each fission reaction produces approximately one more fission reaction. If less than the critical mass Is present, a chain reaction will not occur.

9. Nuclear fusion occurs when two nuclei with low masses are combined to form one nucleus of larger mass.

11. Fusion fuses atomic nuclei together and fission splits nuclei apart. Please copy fission/fusion reactions from the board. How can you tell the difference?

12. For nuclear fusion to occur, positively charged nuclei must get close to each other. But remember they have an electric repulsive Force. If nuclei are moving fast, they can have enough kinetic energy to overcome the repulsive electrical force between them. Only at temperatures of millions of degrees Celsius are nuclei moving so fast that they can get enough for fusion to occur.

13. Most of the energy given off by the sun is caused from the fusion of four hydrogen nuclei into one helium nucleus. One day, all of the hydrogen nuclei will be converted into helium and fusion will stop.

15. http://www.youtube.com/watch?v=G1jtWR_tcX4