## CU1M3 Lab Part 1 Answer Key

2) Please list the shake number and its associated number of parent material and daughter product recovered from each shake of your cup.

Answer: Students will have different numbers for both parent and daughter material for each shake number. If the student starts with 100 parent and ends with 100 daughter, they have done the activity correctly.

 Question CU 1 M3 #2 Student lists all shake numbers and corresponding parent and daughter material numbers accounting for the 100 M&MS   4 pts Student lists all shake numbers and but only parent or daughter material numbers accounting for the 100 M&MS   3 pts Student lists only shake numbers or corresponding parent or daughter material numbers but nothing else   2 pts Student lists very few numbers and it is unclear what the numbers mean   1 pts Insufficient   0 pts

3) Based on decay of your M&Ms, after what shake did you reach your half-life? How do you know?

Answer: Whatever shake corresponds, or is closest to, 50 parent M&Ms left and 50  daughter M&Ms in the students activity. This is because we started with 100 M&Ms and the half-life is the amount of time that it takes for half of the amount of the parent to remain after decay, or in this case, shaking our cup.

 Question CU 1 M3 #3 Student correctly identifies the shake where they reached half-life, defined half-life and described the reasoning behind their inference of which shake determined their half-life   4 pts Student correctly identifies the shake where they reached half-life, and described the reasoning behind their inference of which shake determined their half-life but did not define half-life   3pts Student correctly identifies the shake where they reached half-life, but did not define half-life or correctly described the reasoning behind their inference of which shake determined their half-life   2 pts Student correctly identifies the shake where they reached half-life, but did not define half-life or describe the reasoning behind their inference of which shake determined their half-life   1 pt Insufficient   0 pt

4) What type of function would best fit your data if you were to plot the parent material (Y-axis) vs. shakes (X-axis)? How do you know?

Answer: The function that should best fit the data is an exponential decay function. The reason for that is the decay of the M&Ms is not linear, instead its decay rate is proportional to the current value. So if we plotted this line it would not be straight but a concave down curve. We know because the data points don’t decay at a constant rate.

 Question CU1 M3 #4 Student correctly identifies the best-fit function to describe their data and explains why that type function is correct.   4 pts Student correctly identifies the best-fit function to describe their data and explains why that type function is correct but misses a few key points   3 pts Student correctly identifies the best-fit function to describe their data but does not explain why that type function is correct.   2 pts Student incorrectly identifies best the best-fit function and explains why they think that type of function is correct   1 pt Insufficient   0 pt

9) Is there any way to predict when a specific piece of candy will land marked side up or “decayed”? If you could follow the fate of an individual atom in a sample of radioactive material, could you predict when it would decay? Explain.

Answer: There is no way to accurately predict whether a piece of candy will land marked side up or the decay of a single atom because the events are random. However, one could use statistics in both cases to try and predict when an event will occur based on the behavior of the previous decay of either material, candy or isotope.

 Question CU1 M3 #9 Student correctly answers whether one can predict decay of either candy or atoms and properly explains statistical analysis   4 pts Student correctly answers whether one can predict decay of either candy or atoms and properly explains their answer without describing statistical analysis   3 pts Student correctly answers whether one can predict decay of either candy or atoms but does not properly explains their answer   2 pts Student incorrectly answers whether one can predict decay of either candy or atoms and explains their answer succinctly   1 pt Insufficient   0 pt