**8.01 Half-Life and Radioactive Decay: Half-Life lab**

Time

(seconds)

Data and Observations:

Radioactive atoms

Remaining

Atoms

Decayed

0

3

6

9

12

15

18

21

24

27

30

200

102

51

28

12

5

2

2

1

0

0

0

98

51

23

16

7

3

0

1

1

0

Data and Observations

Time

(seconds)

Radioactive atoms remaining

(not decayed)

Atoms

Decayed

0

3

6

9

12

15

18

21

24

27

30

200

107

57

34

16

6

3

1

1

0

0

0

93

50

23

18

10

3

2

0

1

0

1) Determine the average number of atoms remaining (not decayed) at each three-second time interval by adding the results from the two trials and dividing by two.

2) Create a table that compares time to the average number of atoms remaining at each time interval.

3) Create a graph of your data showing the average number of atoms remaining versus time.

Calculations

Time

(seconds)

Average number of

atoms remaining

0

200

3

104.5

6

9

12

15

18

21

24

27

30

54

31

14

5.5

2.5

1.5

1

0

0

1) 3 shakes for both trials.

2) 3 Seconds

3) 12 atoms

4) No, because the slope of the graph is still negative. The only thing that would change is the decay time.

5) Table 1: (0/200)100 = 0%, (98/20)100 = 49%, (51/102)10 = 50%, (23/102)100 = 23%, (16/51)100 = 31%, (7/51)100 = 14%, (3/28)100 = 11%, (0/28)100 = 0%, (1/12)100 = 8%, (1/12)100 = 8%, (0/5)100 = 0%

Table 2: (0/200)100 = 0%, (91/200)100 = 46%, (50/107)100 = 47%, (23/107)100 = 21%, (18/57)100 = 32%, (10/57)100 = 18%, (3/34)100 = 9%, (2/34)100 = 6%, (0/16)100 = 0%, (1/16)100 = 6%, (0/6)100 = 0%.

6) The activity modeled the half-life concept very closely. My calculations from the previous question give the rate that the material decayed at in the experiment.

7) I believe the experiment went better after 12 seconds.

Conclusion Answers

1) After how many time intervals (shakes) did one-half of your atoms (candies) decay?

2)What is the half-life of your substance?

3) If the half-life model decayed perfectly, how many atoms would be remaining (not decayed) after 12 seconds?

4) If you increased the initial amount of atoms (candies) to 300, would the overall shape of the graph be altered? Explain your answer.

5)Go back to your data table and for each three-second interval divide the number of candies decayed by the number previously remaining and multiply by 100. Show your work.

6)The above percentage calculation will help you compare the decay modeled in this experiment to the half-life decay of a radioactive element. Did this activity perfectly model the concept of half-life? If not, was it close?

7)Compare how well this activity modeled the half-life of a radioactive element. Did the activity model half-life better over the first 12 seconds (four decays) or during the last 12 seconds of the experiment? If you see any difference in the effectiveness of this half-life model over time, what do you think is the reason for it?

Conclusion Questions