Gizmo Half Life Answer Key

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Half Life is one of the science materials on Gizmo that allows you to explore and measure the decay of a radioactive substance. A radioactive atom can change at any time and change by emitting radiation in the form of tiny particles and/or energy. Well, this process is called decay that causes the radioactive atom to change into a stable daughter atom.

On Gizmo, you will be required to take the Gizmo Half Life test, after learning about this material. If you are accidentally looking for Gizmo Half Life answers, you definitely can find those answers in our post. Okay, let’s dive into our post below!

Gizmo Half Life Answers

In this post, we will show you the Half Life answers on Gizmo from  The test about Half Life consists of three sections: Warming up, Activity A and B. The correct answers are highlighted in bold font.

Warming Up

There are several warming up questions you should answer before taking the activity A and B test. Here are they:

  1. What do you see and hear? There is a static sort of popping sound as the atoms turn from red to bluish gray.
    It’s important to 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? The rate of decay is fastest near the beginning.

Activity A – Decay Curves

To take this test, you can click ‘Reset’ and make sure that User chooses half-life and Random decay are selected. You can then 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?

Answer: 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.

Answer: No, the numbers of daughter atoms increase steadily while towards the end of the reaction, the radioactive atoms take longer to disappear.

  1. Experiment: You can click Reset and select the ‘Graph’ tab. Run a simulation with the Half-life set to 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.


How do we measure the rate of radioactive decay

  1. Interpret: How does the Half-life setting affect how quickly the simulated substance decays?

Answer: When it’s at 5 seconds it goes faster

  1. Collect data: Click Reset. Change the Half-life to 10 seconds and click Play. Select the TABLE tab and record the number of radioactive atoms at each given time below.


0 s: 128
10 s: 55
20 s: 28
30 s: 11
40 s: 6
50 s: 3

  1. Analyze: What pattern, if any, do you see in your data?

Answer: no pattern

  1. Revise and repeat: Use your data from #4 above to fill in the first line of the data table below. Then repeat the experiment four more times. Calculate the average number of radioactive atoms for each time.


Trial 0 s 10 s 20 s 30 s 40 s 50 s
1 128 55 28 11 6 3
2 128 71 33 17 11 7
3 128 58 27 16 4 3
4 128 64 32 17 9 5
5 128 60 31 12 5 2
Averages 128 61.6 30.2 14.6 7 4
  1. Analyze: A half-life is defined as the amount of time it takes for half of the radioactive particles to decay. For the simulated substance, every 10 seconds represents one half-life.

How does your data demonstrate the definition of a half-life?

Answer: It has an average of being half of the last half life

  1. Revise and repeat: Click Reset. Real radioactive samples will contain billions of radioactive atoms. Tomodel the decay of a large sample, change from Random decay to Theoretical decay on the SIMULATION pane.

To answer this question, you can click ‘Play’ and record the numbers of radioactive atoms:


0 s:128
10 s:64
20 s:32
30 s:16
40 s:8
50 s:4

How does this data demonstrate the meaning of half-life?

Answer: The reactive atoms half everytime

Activity B – Measuring Half-Life


Different isotopes of the same element have the same number of protons but different numbers of neutrons in the nucleus. Some isotopes are radioactive.

Question: How do we find the half-life of a radioactive isotope?

  1. Observe: Select the GRAPH tab, and click Play. Based on the graph, what is your estimate of the half-life of isotope A?

Answer: 15

  1. Measure: Turn on the Half-life probe. Use the probe to measure how long it takes for exactly one-half of the original radioactive atoms to decay. What is the exact half-life of isotope A?

Answer: 31

  1. Collect data: In the first row of the table below, write how many seconds represent one half-life, two half-lives, and so forth. On the next row, predict the number of radioactive atoms that will be present at each time. Then use the probe to find the actual values.


Half-life 0 1 2 3 4 5
Time (Seconds) 0 31 62 94 125 155
Predicted # Radioactive atoms 128 64 32 16 8 4
Actual #

Radioactive atoms

128 64 32 16 8 4
  1. Calculate: Calculate the percentage of radioactive atoms that are left after each half-life.


Half-life 0 1 2 3 4 5
Percentage radioactive atoms 100 50 25 12.5 6.25 3.125
  1. Apply: Suppose you found a material in which 12.5% of the original radioactive atoms were present. If the half-life is 47 years, how old is the material?

Answer: 196 years old

  1. Apply: Use the Gizmo to find the half-life of Isotope B. What is it?

Answer: 17

As we have mentioned, Gizmo Half-Life test consists of three sections. In this post, however, we can only show you some of them. If you want to get more questions and answers of Gizmo Half-Life, you can visit,  since this site will always show you any kinds of science test answers.

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