Safety Symbols: Sharp Instrument Safety Name Answer Key

Date __________________ Period _____

Teacher ________________ Seat # _____

Radioactive Decay Lab

Problem: Accept any reasonable response

Hypothesis: Accept any reasonable response

Materials:

Graph paper Two licorice sticks – different colors (e.g., red and chocolate)

Scissors Two colored pencils – matching licorice colors

Metric ruler Watch with second hand

Procedure: Observation:

1. Use the scissors to cut one licorice 1. ______________________________________

stick to a length of 160 mm.

2. Use the watch as a timer to count a 2. ______________________________________

four-second interval, use the ruler to

determine the midpoint of the licorice ______________________________________

stick, and cut the stick in half at the end

of four seconds. Remove one of the two ______________________________________

halves by eating it to represent radioactive

decay. Record the length of the remaining ______________________________________

half in the Data Table.

3. Repeat step number 2 as many times as 3. ______________________________________

you can until the remaining licorice stick is

too small for you to measure accurately. ______________________________________

4. Plot the values in your data table on 4. ______________________________________

graph paper according to the teacher’s

directions. The time should be plotted on ______________________________________

the x-axis and the lengths should be plotted

on the y-axis. ______________________________________

5. Use the scissors to cut the second 5. ______________________________________

licorice stick to a length of 100 mm.

6. Using Table B below, cut the 6. ______________________________________

licorice stick so that the total length

equals the next value in the table below. ______________________________________

Remove the “decayed” portion by eating

it. ______________________________________

7. Repeat step number 6 for each column 7. ______________________________________

in Table B below.

8. Plot the values in Table B on the same 8. ______________________________________

graph that you used for your data from the

first licorice stick.. ______________________________________

Table B:

Time (sec)	0	2	3	5	8	13	15	18	22	25	30
Remaining Length (mm)	100	80	71	59	46	31	26	20	14	11	8

Data Table:

Time (sec)	0	4	8	12	16	20	24	28
Remaining Length (mm)	160	80	40	20	10	5	2.5	1.25

Data Graph:

Questions:

1. What is the half-life of the first licorice stick? 4 seconds

2. What is the half-life of the second licorice stick? 7 seconds

Conclusion: Accept any reasonable response. Students should recognize the meaning of

half-life and be able to interpret it for both of the licorice stick examples. Students may also

observe that even though half of the licorice “decays” during the initial half-life, it takes many

half-lives for the remaining amount to “decay”.