A100 gram sample is left undisturbed for 8 hours. at the end of that period, only 12.5 grams remain. what is the half-life of this sample?

The half-life of a radioactive substance describes the amount of time required for half of that radioactive substance to decay into a different form.

In this situation, 100 grams decays into 12.5 grams over the course of 8 hours. We have half lives that look like this -

100 grams - 50 grams (1) - 25 grams (2) - 12.5 grams (3)

three half lives have passed since the start over the course of eight hours, so:

8 hours/3 half-lives = ~2.667 hours per half-life

The half-life of this substance is approximately 2.667 hours.

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