Name: Date:
Student Exploration: Half-life
Vocabulary: daughter atom, decay, Geiger counter, half-life, isotope, neutron, radiation,radioactive,
radiometric dating
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Have you ever made microwave popcorn? If so, what do you hear while the popcorn is in the
microwave? Yes, I hear the kernels popping in the bag.
2. If you turn the microwave on for two minutes, is the rate of popping always the same, or does itchange?
Explain. The rate of popping is not always the same because when you first put
the bag of popcorn in and start the microwave, there is not a lot of popping, but when the
contents of the bag begin to heat up, the popping increases. By the end of the cooking
session, all of the kernels should be popped so there is no more popping.
Gizmo Warm-up
Like an unpopped kernel in the microwave, a radioactiveatom
can change at any time. Radioactive atoms change by emitting
radiation in the form of tiny particles and/or energy. This
process, called decay, causes the radioactive atom to change
into a stable daughter atom.
The Half-life Gizmo™ allows you to observe and measurethe
decay of a radioactive substance. Be sure the sound is turned
on and click Play ( ).
1. What do you see and hear? There is a static sort of popping sound as the atoms turnfrom red
to blueish gray.
Note: The clicking sound you hear comes from a Geiger counter, an instrument that detectsthe particles
and energy emitted by decaying radioactive atoms.
, 2. What remains at the end of the decay process? Daughter Atoms
3. Is the rate of decay fastest at the beginning, middle, or end of the process? The rate ofdecay is
fastest near the beginning.
Get the Gizmo ready:
Activity A: ● Click Reset ( ). Be sure that User chooses
half-life and Random decay are selected.
Decay curves ● Check that the Half-life is 20 seconds and the
Number of atoms is 128.
Question: How do we measure the rate of radioactive decay?
1. Observe: Select the BAR CHART on the right side of the Gizmo and click Play.
A. What happens to the numbers of radioactive and daughter atoms as the simulation
proceeds? The number of radioactive atoms decreases until they reach zero
and the number of daughter atoms increases.
B. Do the numbers of radioactive and daughter atoms change at the same rate throughout the
simulation? Explain. No, the numbers of daughter atoms increase
steadily while towards the end of the reaction, the radioactive atoms take
longer to disappear.
2. Experiment: Click Reset, and select the GRAPH tab. Run a simulation with the Half-life setto 5
seconds, and then run another simulation with the Half-life set to 35 seconds. Sketch each resulting
decay curve graph in the spaces below.
Student Exploration: Half-life
Vocabulary: daughter atom, decay, Geiger counter, half-life, isotope, neutron, radiation,radioactive,
radiometric dating
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Have you ever made microwave popcorn? If so, what do you hear while the popcorn is in the
microwave? Yes, I hear the kernels popping in the bag.
2. If you turn the microwave on for two minutes, is the rate of popping always the same, or does itchange?
Explain. The rate of popping is not always the same because when you first put
the bag of popcorn in and start the microwave, there is not a lot of popping, but when the
contents of the bag begin to heat up, the popping increases. By the end of the cooking
session, all of the kernels should be popped so there is no more popping.
Gizmo Warm-up
Like an unpopped kernel in the microwave, a radioactiveatom
can change at any time. Radioactive atoms change by emitting
radiation in the form of tiny particles and/or energy. This
process, called decay, causes the radioactive atom to change
into a stable daughter atom.
The Half-life Gizmo™ allows you to observe and measurethe
decay of a radioactive substance. Be sure the sound is turned
on and click Play ( ).
1. What do you see and hear? There is a static sort of popping sound as the atoms turnfrom red
to blueish gray.
Note: The clicking sound you hear comes from a Geiger counter, an instrument that detectsthe particles
and energy emitted by decaying radioactive atoms.
, 2. What remains at the end of the decay process? Daughter Atoms
3. Is the rate of decay fastest at the beginning, middle, or end of the process? The rate ofdecay is
fastest near the beginning.
Get the Gizmo ready:
Activity A: ● Click Reset ( ). Be sure that User chooses
half-life and Random decay are selected.
Decay curves ● Check that the Half-life is 20 seconds and the
Number of atoms is 128.
Question: How do we measure the rate of radioactive decay?
1. Observe: Select the BAR CHART on the right side of the Gizmo and click Play.
A. What happens to the numbers of radioactive and daughter atoms as the simulation
proceeds? The number of radioactive atoms decreases until they reach zero
and the number of daughter atoms increases.
B. Do the numbers of radioactive and daughter atoms change at the same rate throughout the
simulation? Explain. No, the numbers of daughter atoms increase
steadily while towards the end of the reaction, the radioactive atoms take
longer to disappear.
2. Experiment: Click Reset, and select the GRAPH tab. Run a simulation with the Half-life setto 5
seconds, and then run another simulation with the Half-life set to 35 seconds. Sketch each resulting
decay curve graph in the spaces below.
