Thursday, August 27, 2015
Sunday, July 12, 2015
Saturday, February 8, 2014
Friday, December 20, 2013
STEM Project - Atomic Candy
Atomic Candy - Radioactive Decay
(activity from http://teachers.egfi-k12.org/radioactive-decay-lesson/)LEARNING OUTCOMES
Students will understand the concept of half-life.
Students will understand the radioactive decay process.
Students will create and interpret half-life exponential graphs.
Students will understand the difference between a linear and exponential progression.
(Image from:
SCIENCE
Students will understand the science of radioactive decay. The probability that an atom will decay remains the same over time but we do not know which atoms will decay. We can graph how the decay happens as fewer and fewer radioactive atoms remain.
ENGINEERING
Radioactive isotopes are used in medical applications and equipment and facilities are designed by engineers. In this project students will create a simulation and record radioactive decay, which requires precision.
TECHNOLOGY
Students will use materials to simulate the radioactive decay.
MATHEMATICS
Students will gather data, plot the ordered pairs in the coordinate plane. Distinguish between linear and exponential functions. Prove that linear functions grow by equal difference over equal intervals and exponential functions do not. Will be able to read the graph to determine if the quantity is growing or decaying.
INSTRUCTIONS
Introduction and Discussion
What is an isotope?
An isotope is any of the two or more forms of the same element. All elements have protons and neutrons in the nucleus. Isotopes have the same number of protons but different number of neutrons and therefore differ in their atomic mass but not in their chemical properties.
For example, Carbon-12, Carbon-13 and Carbon-14 are isotopes of Carbon and have the same atomic number 6 which is the number of protons in the nucleus. The number of neutrons are 6, 7, and 8 and therefore the atomic mass is 12, 13, and 14 respectively.
What is a radioactive isotope?
A radioactive isotope is an unstable form of isotope. There are over 1000 radioactive isotopes of the known elements, of which about 50 are found in nature and the rest are produced artificially.
Why do we need radioactive isotopes?
Radioactive isotopes have many applications. In medicine, cobalt-60
is used as a radiation source to treat cancer. When small amounts of a
radioactive isotope are added to the stable isotope it makes easier to
use and is often used in medical diagnosis. For example, Iodine-131 is
used to trace brain tumors and measure cardiac output.In industry radioactive isotopes are used to measure the thickness of metal. Isotopes are also sources of energy such as electric power and are used in pace-makers for the heart.
What is a half-life?
An unstable radioactive isotope loses particles and releases energy. It loses these particles or decays randomly. We cannot predict which atom will decay but we know the probability that an atom will decay remains the same over time. The length of time required for half the isotope atoms to decay is called half-life. Different isotopes have different half-lives and can linger on for a very long time. All decay graphs have a similar shape.Experiement
After introduction and discussion of isotopes give instructions on the simulation atomic decay.
M&ms will be used as radioactive atoms and we will record how they decay. We know that any radioactive atom has the same probability of decay at any time, we also know that if we toss an m&m on the table we have an equal probability that it will land with the letter side up or the letter side down.
1. Have 100 m&m atoms in a sealed bag.
2. Gently shake the bag for 10 seconds.
3. Gently pour out the candy and count the number of peaces that have m printed on it. These atoms have decayed. Record your data.
4. Remove the decayed candy and refill the bag with the remaining candy.
5. Repeat steps 2 to 4 until all atoms are decayed.
6. Graph the number of undecayed atoms vs. time.
Supplies
Graph paper
M&ms
Resealable bag
Paper towels to place on desks to pour out the candy on.
Discussion after first experiment
1. What is a half-life?
Half-life is the length of time required for half the isotope to decay.
2. In this experiment what is the half-life of the isotope candy?
10 second (the number may not be an exact 50% of all candy).
3. At the end of two half-lives what fraction of the atoms are not decayed?
At the end of two half-lives 1/4 th of the original candy sample remains)
5. Repeat experiment with 30, 50, and 80 candy atoms and compare the graphs.
The graphs should be almost the same.
Data and Observations Table
Total Time (sec) # of Undecayed Atoms # of Decayed Atoms
0
10
20 Etc.
Further discussions
What type of graph is it? Linear? Exponential?
Show examples of graphs.
Graphs from (http://www.bymath.com/studyguide/fun/sec/fun9h.gif
Experiment
Total time (sec)
|
Total time
(sec)
|
# of
undecayed atoms
|
# of
decayed atoms
|
|
0
|
100
|
0
|
|
10
|
60
|
40
|
|
20
|
32
|
68
|
|
30
|
15
|
85
|
|
40
|
8
|
92
|
|
50
|
5
|
95
|
|
60
|
4
|
96
|
|
70
|
2
|
98
|
|
80
|
2
|
98
|
|
90
|
1
|
99
|
|
100
|
0
|
100
|
|
|
|
|
|
Total time
(sec)
|
# of
undecayed atoms
|
# of
decayed atoms
|
|
0
|
80
|
0
|
|
10
|
41
|
39
|
|
20
|
19
|
61
|
|
30
|
11
|
69
|
|
40
|
7
|
73
|
|
50
|
6
|
74
|
|
60
|
5
|
75
|
|
70
|
0
|
80
|
|
|
|
|
|
Total time
(sec)
|
# of
undecayed atoms
|
# of
decayed atoms
|
|
0
|
50
|
0
|
|
10
|
24
|
26
|
|
20
|
13
|
37
|
|
30
|
5
|
45
|
|
40
|
5
|
45
|
|
50
|
2
|
48
|
|
60
|
0
|
50
|
|
|
|
|
|
Total time
(sec)
|
# of
undecayed atoms
|
# of
decayed atoms
|
|
0
|
30
|
0
|
|
10
|
16
|
14
|
|
20
|
12
|
18
|
|
30
|
6
|
24
|
|
40
|
0
|
30
|
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