Day 9: Revisiting the Models

Let's start with a look at the BIG Questions.  What comments can you add now?

Take a look at four of the public service videos that your class made.   What are some of the strengths and weaknesses you see?   How do we get people to buy a message that we are sending? Write your thoughts on a whiteboard.









Class Conversation

Individual Problems

• An object taken from a cave has a carbon-14 fraction which is 0.89 of the amount in a

living organism. How old is the object? (half-life for C-14 is 5730 yr)

• Write nuclear equations for the following processes:
  a. Ra-226 decays by α-emission.
  b. The result of the β-decay of an isotope is Mg-22.

• For the following, calculate the value of time elapsed for four half-lifes ofthe isotope:
  a. Th-227, 18.2 day
  b. Pa-234, 6.75 hr
  c. Rn-222, 3.823 day

• The half-life of Pa-234 is 6.75 hr. How much (what fraction) of a sample of this isotope remains after 20.25 hr?
• The half-life of Rn-222 is 3.823 day. What was the original mass of a sample of this isotope if 0.0500 g remains after 7.646 day?