The half-life of iron-61 is 6 minutes. If a sample originally contains 8 g of the isotope, how much remains after 18 minutes? Write 2 – 3 sentences explaining your reasoning.

Answer the questions below.

Question 1: Nuclear Structure (10 points)

a. Protons and neutrons make up the nucleus of an atom. Write 3 – 4 sentences describing the electrostatic force between each pair of particles (proton-proton, proton-neutron, neutron-neutron) and the strong nuclear force between each pair of particles. (5 points)

b. Write 3 – 4 sentences predicting the changes in electrostatic force, strong nuclear force, and the stability of a nucleus if the number of neutrons is increased. (3 points)

c. Write 2 – 3 sentences describing Einstein’s explanation for why the total starting mass is greater than the total ending mass after a nuclear reaction. (2 points)

Question 2: Radioactivity (7 points)

a. Write 2 – 3 sentences describing the mass number, charge, and penetrating ability of alpha particles. (3 points)

b. Write the symbol for the nucleus that completes the nuclear equation:

(2 points)

c. Write the symbol for the nucleus that completes the nuclear equation:

(2 points)

Question 3: Half-life (4 points)

a. The half-life of iron-61 is 6 minutes. If a sample originally contains 8 g of the isotope, how much remains after 18 minutes? Write 2 – 3 sentences explaining your reasoning. (2 points)

b. The ratio of carbon-14 to nitrogen-14 in an artifact is 1:3. In other words, ¼ of the original carbon-14 remains. Given that the half-life of carbon-14 is 5730 years, how old is the artifact? Write 2 – 3 sentences explaining your reasoning. (2 points)

Question 4: Fission and Fusion (9 points)

a. Write 2 – 3 sentences describing what happens to a uranium nucleus during nuclear fission. (2 points)

b. Write 2 – 3 sentences explaining why nuclear fusion cannot be used in power plants, yet can still be the original source of the electric energy used in homes. (4 points)

c. Write 3 – 4 sentences evaluating the use of nuclear fission to generate electric energy. Provide at least one point in favor of and two points against using fission. (3 points)

Question 5: Quantization (8 points)

a. What is a blackbody radiator? (1 point)

b. What was the ultraviolet catastrophe? (1 point)

c. Explain what is meant by quantized light. (1 point)

d. Explain why observations of blackbody radiation provide evidence for the quantization of light. (2 points)

e. Write 2 – 3 sentences explaining how quantum mechanics describes light and matter. How does the interference pattern of electrons support the idea that matter can behave as a wave? (3 points)

Question 6: Relativity (6 points)

a. How does the speed of light in a vacuum change when observed from two different frames of reference? (2 points)

b. Which frames of reference can be studied using special relativity? (2 points)

c. A stationary observer measures an object that is traveling at nearly the speed of light. Describe how the length of this object compares with the length of an identical object that the observer is holding. Write 1 or 2 sentences explaining your reasoning. (2 points)

Question 7: Cosmology (6 points)

a. Write 2 – 3 sentences identifying the most widely accepted theory for the formation of the universe. In your description, be sure to include how the universe began and what is happening to the size of the universe today. (2 points)

b. Write 2 – 3 sentences explaining redshift and what it led scientists to conclude about the universe. (2 points)

c. Scientists have proposed three models of the universe: flat, open, and closed. Each of these describes a different future for the universe. Write 2 – 3 sentences identifying the model that is most widely accepted and describing the future of the universe according to that model. (2 points)

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