Half-life GIZMO Latest Update Score Yourself An A+

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? The sound of the kernels popping.

2. If you turn the microwave on for two minutes, is the rate of popping always the same, or

does it change? Explain. It changes. It starts with no popping. Then fast popping. And lastly

slow popping.

Gizmo Warm-up

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.

The Half-life Gizmo allows you to observe and measure

the decay of a radioactive substance. Be sure the sound

is turned on and click Play ( ).

1. What do you see and hear? I saw the radioactive atoms quickly then slowly turn into

daughter atoms. I heard electric zappy noises.

Note: The clicking sound you hear comes from a Geiger counter, an instrument that detects

the 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? Beginning

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 amount of daughter atoms increases, and radioactive atoms decrease. B. Do the numbers of radioactive and daughter atoms change at the same rate throughout the simulation? Explain. No. It is at it’s fastest at the beginning of the simulation. 2. Experiment: Click Reset, and select the GRAPH tab. Run a simulation with the Half-life set to 5 seconds and another simulation with the Half-life set to 35 seconds. 3. Interpret: How does the Half-life setting affect how quickly the simulated substance decays? The time it would take for radioactive atoms to turn to daughter atoms would decrease if the half-life were shorter. (Activity A continued on next page)