Physical Science with Ms. Sherman



Name: _______________________________________________________________ Date: ___________________

Half-lives

it’s a good thing we don’t have ‘em (

A.) Gaining knowledge through READING!

Step 1.) Please read the following excerpt and highlight or underline the answers to the questions on the side.

B.) Half-life Introduction and Explanation- VIDEO

Step 1.) Examine the information below that you need to pay attention to as you watch the videos for this next section.

Step 2.) Go to the Unit 5 page of my website and watch videos titled “Nuclear Half Life: Intro and Explanation”. As you are watching please follow the “while-watching” instructions below.

While-watching instructions: For each video, write down and/or draw on a separate sheet of paper …..

❖ Write down/take notes based on what the dude (Tyler) writes.. pretend as though you are in class!

❖ What fraction of substance X is left after…..1 half-life? …..2 half-lives? ……3 half-lives?

❖ What symbol is used to represent half-life?

❖ What are the labels for the x- and y-axes of the half-life graph?

C.) Calculating Half-life: A How-To

Step 1.) Go to the Unit 5 page of my website and watch the “Nuclear Half Life: Calculations” video. As you do, follow along with Tyler (the guy in the video) and ON A SEPARATE SHEET OF PAPER write down the problems and follow along as you would in class. Please do AT LEAST 2 out of the 3 problems. Don’t sell yourself short. If you need to watch all 3, spend the time doing it. If you think you get it after the first 2, then you don’t need to watch the third. **BE SURE TO PUT A TITLE ON YOUR PAGE**

D.) Analyzing/Interpreting Half-life Graphs

Answer the questions below by analyzing/interpreting the graphs and using your prior knowledge about half-life.

[pic]

[pic]

12. Will radioactive samples ever go away? Explain your logic.

E.) Calculating Half-life, LET’S DO IT! WOOHOO!

1.) The half-life of 86Rn gas is 4 days. Starting with 10.0 mg of the isotope, what amount would decay in 16 days? What amount would remain?

2.) A certain isotope has a half- life of 15.0 min. In what period of time would the activity be reduced to approximately one eighth of the original?

3.) The half-life of 214 82Pb is 27 min. Starting with 64.0 mg. of this isotope, what is the remaining quantity at the end of 2.o hours and 15 min.?

4.) The 23892U isotope which occurs naturally, has a half-life of 4.5 x 109 years. In what period of time would the activity be reduced to 1/8 of the original?

5.) A piece of charcoal found in a cave from a wood fire shows an activity of 25% of freshly prepared charcoal. Estimate the age of the sample in half-lives.

6.) A radioactive isotope has a half-life of 2.0 hours. Starting with 3.2 x 102 atoms, how many atoms will be left at the end of 10 hours?

7.) Determine the half-life of an element, 88% of which decays in 2 years.

8.) The half-life of 3516S is 87 days. Starting with 8.0 x 105 atoms, how many atoms of this isotope would decompose in 261 days?

*EXTRA CHELLENGE* What is the half-life of a radioactive element ¾ of which decays in 10 hours?

*EXTRA CHELLENGE* The half-life of francium is 21.0 mins. Starting with 4.0 x 1018 atoms of francium, how many would decompose in one hour and 3 minutes?

-----------------------

❖ How do scientists determine the age of materials such as rocks and cloth?

❖ What is the value that scientists use to predict the age of materials?

❖

❖ What is half-life?

❖ Is the following statement true or false? If it’s false, correct it. “Every substance has the same half-life.”

1. What is the ½ life of Cesium 137 in years? ___________________

2. How much of the sample is left after 5 half lives? _______________

3. What is the ½ life of Strontium 90? __________

4. How many years have gone by during 10 half lives? _____________

5. How much of my sample is left after 112.4 years? ________________

Carbon-14 Decay

6. What is the ½ life of Carbon 14? __________________

7. About how much of the sample is left after 4 half lives? ___________________

8. What is the ½ life of Uranium-238? ___________________

9. How much time has gone by when you only have 6.25 % of your sample remaining? _____________

10. How many days have gone by with 25% of the sample remaining? ________________

11. What is the half life of Iodine 131? ___________________

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download