Mario places 10 ml of water in a test tube and heats the liquid over a bunsen burner for 2 minutes. after removing the test tube from the bunsen burner, there are 6 ml of water left in the test tube. this experiment is a good example of a a. chemical change involving chemical reactions. b. physical change involving chemical reactions. c. physical change involving phase changes. d. chemical change involving phase changes.

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.