ExploreLearning Gizmo: Half-life
Warm-up
1. How long does it take you, on average, to pop a bag of popcorn
in the microwave? (Note: This is an estimate. There’s no right or wrong answer.
It’s an analogy to get you thinking about how radioactive decay works.)
2 mins and 50 seconds
2. If you turn the microwave on for 2 minutes, is the rate of popping
always the same, or does it change/fluctuate? Explain.
No, it is inconsistent
because the number of
pops will increase and
decrease.
Like an unpopped kernel in the microwave, a radioactive atom 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.
This Gizmo allows you to observe and measure the decay of a radio-
active substance. Be sure the sound is turned on and click Play ( ). ▶
3. Observe, then describe what you see and hear. The pops happened inconsistently and
they slowed down over time.
(Note: The clicking sound you hear comes from a Geiger counter, an instrument that detects the
particles and energy emitted by decaying radioactive atoms.)
4. What remains at the end of the decay process? The daughter atoms remain.
5. Is the rate of decay fastest at the beginning,
middle, or end of the process?
It is the fastest at the beginning
of the process.
Activity A:
Decay curves
Get the Gizmo ready:
●Click Reset ( ). Be sure that User chooses half-life and Random
decay are selected.
●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?
6. Observe : Select the BAR CHART on the right side of the Gizmo and click Play.
1. What happens to the numbers of radioactive and
daughter atoms as the simulation proceeds?
The radioactive goes down
and the daughter atoms go
