HW #9 for 3/1

1) HW #9 PG 696 #43-48
2) Nuclear test on Thur. 3/3--check the study guide
3) Pi day coming up Mon. 3/14—sign ups tomorrow

HW #8 for 2/29

1) HW #8 pg. 695 #33-38
2) Pi day on Monday, March 14th--sign ups next week
3) Test next Wednesday
4) Composition books due next week

HW #7: for 2/25

HW #7
1) pg. 691 #1-6

Nuclear Energy Resources

Links for Nuclear Energy Research
NY Times post-Fukishima #1
NY Times article post-Chernobyl
Nuclear power plants background information
Pros/Cons nuclear energy
Info for students about nuclear energy
Nat Geo nuclear energy info
Ted Talk Debate
Dept of Energy nuclear data

HW # 6 for 2/23

1) HW #6: pg. 695 #27-30

Take Home Lab #3

Take Home Lab #3:  Half-Life Simulation

Question: What is the half-life of a simulated nuclear reaction?

Safety: Be careful with the scissors and keep them out of the reach of small children.

Materials: copy of provided paper, scissors, a box

Procedure: In this lab, you will simulate the graphing of the half-life of a radioactive substance using slips of paper. A half-life is defined as the time that it takes for half of a radioactive material to decay into another substance. You will simulate this process by flipping some papers and taking out all that are facing the same direction and continuing. The papers with the symbol facing down represent atoms that are radioactive. Those facing up have already decayed.

                Cut out all the pieces of paper with the Greek letter a (Alpha) on them. Put them in a box and shake them up. Take out all the pieces that have the a facing up. Count and record how many are left. Shake the box again, and again remove all of the pieces that have the a facing up. Count and record how many are left. Continue this until no pieces are left. Repeat this procedure one more time.

Data Table:

Trial number:	Number of papers left:
1	100
2
3
4
5
6
7

Prepare a graph with trial # on the x-axis and the number of papers left on the y-axis.

 

Papers

left

 

                                                Trial #

Post-Lab Questions:

1. How many shakes did it take to get rid of all the papers?

2. Use your graph to interpolate the half-life if each shake represents 1,000 years.

3. Use your graph to answer the question, “How many years have passed when 25% of the papers are left?”

4. According to your data, what is the oldest object that this method could be used to date?

HW #5 for 2/22

1) HW #5: pg. 682 #1-2, 4, pg. 695 #21, 23-24
2) Take Home Lab #3 due Mon 2/22
3) Periodic Assessment Monday

Pennies Half Life Lab

Pennies Half Life Lab

Background: Uranium-238 or U-238 is a radioactive isotope of the element uranium.  Uranium-238 decays to lead-206, which is a stable isotope of the element lead.  The half-life of uranium-238 is 4.5 billion years. So every 4.5 billion years, half of the uranium-238 atoms in a sample will decay to lead-206.  In other words, during any 4.5 billion year period, the probability that a particular uranium-238 atom will decay is ½.

            The absolute age of a rock can be found by analyzing the rock for uranium-238 and lead-206. Knowing the amounts of both of these isotopes enables scientists to calculate how long ago the rock formed. In the following experiment, you will use pennies to model radioactive decay.

Objectives:

1.      To model radioactive decay using pennies to represent uranium atoms. 

2.      To demonstrate the concept of half-life and how it is used in radiometric dating.

Pre-Lab Questions:

1. Define the term “half-life”.

2. What does it mean when we say that an atom has “decayed”?

3. If you start with 8,000 atoms how many will you have left after four half-lives? Show your work.

4. If you start with 1,920 atoms and now have 240 atoms left, how many half-lives have past? Show your work.

Hypothesis:

1. Calculate if you have ___ atoms, how many half-lives will it take until you have zero atoms left.

2. How many shakes do you think you will need to remove all your pennies from the box.

Procedure:

1. Place ____ pennies in your plastic cup.  Put your hand over the cup and shake it several times.

2. Shake the pennies out into your box until they are all flat on the box.

3. Remove all the pennies from the box that are _____ side are turned upward.

4. Count how many pennies you removed and how many pennies that you have left in the box. Record in the data table.

5.  Remove all the pennies from the box and place in the cup and shake out again.

6. Repeat the steps again until there are no pennies left in your container.

7. Repeat the steps again for a second trial until there are no pennies left again and record your data.

Shake number:		Number of pennies remaining:		Number of pennies removed:
Trial #1	Trial #2	Trial #1	Trial #2	Trial #1	Trial #2:
1	1
2	2
3	3
4	4
5	5
6	6
7	7

Analyzing your results:

1. Use the graph data example on the screen to graph your results.

2. Make sure to label your axes on your graph.

3. Graph trial #1 and trial #2 on your graph with two different colors. 

4. Draw a smooth line/curve to connect your points for each of your trials.

5. Write your results on the class data sheet at the front of the room.

Post-lab questions:

1.  Examine the half-life of uranium-238 graph on the screen and the graph you have made.  Does the lines/curves have the same shape?  Explain why or why not.

2. Assume that the pennies represent uranium-238 and lead-206 isotopes. Remember that uranium-238 is the parent isotope and decays to lead-206 the daughter isotope.  In this model, which isotope represents the “head” side of the penny? Which isotope represents the “tail” side of the penny?

3. If a “sample” of pennies had 75 heads and 25 tails showing, how many half-lives would have passed since the “sample” had formed and begun to decay?  (Hint: the original sample had 100 tails. Which each half-life, half of the pennies became heads.  How many half-lives does it take to get to 75 heads?)

4. Do you think the number of pennies (or atoms) you start with affect the outcome? Explain.

5. Describe the shape of the line/curve you made with your graph.  What does that shape tell you about the results?

HW #4 for 2/18

1) HW #4: pg. 694 #12 b-c, 14-18
2) Test make up due Fri. 2/19

HW #3 for 2/16

1) HW #3 pg. 673 exer 19.1 (yellow box), pg. 674 exer 19.2 (yellow box), pg 678 #3, pg. 694 #12
2) Test make ups due on Friday, February 19th.  Write out corrections SHOWING work on a separate piece of paper and staple to your original test.

Reading Questions for Sec 19.1

Section 19.1: Reading Questions (pg. 668-677) on pg. 39

1. It states in your text that there are about 2000 nuclides known. How can this be possible if there are only about 100 elements?

2. Write the charge, mass number, and symbol for a beta particle and an alpha particle.

3. By how many units does the mass number of a nucleus change when the nucleus produces an alpha particle?  By how many units does the mass number of a nucleus change when the atom produces a beta particle?  Is each change an increase or a decrease in mass number?

4. Draw what it looks like when a beta particle leaves the nucleus.

Draw what it looks like when an alpha particle leaves the atom.