Year 10 Science · Unit 2 · Lesson 24

Radioactive Half-Life

Foundation Worksheet

Name

Date

Class

Learning Goals

Recall what half-life means and that it is constant for a given isotope.
Sort terms and isotopes into the correct categories.
Complete a simple halving table to show how a sample decays.

Warm Up

Fill the gap

Choose the correct word from the word bank to complete each sentence. Two words will NOT be used.

stable activity eighth unstable constant half decay half-life isotope double

A radioactive nucleus is and breaks down over time in a process called radioactive . The time taken for of the radioactive nuclei in a sample to decay is called the . This value is for a given , so it does not change with temperature or the amount of sample. As nuclei decay, the of the sample, the number of decays per second, falls. After three half-lives, only one of the original sample remains.

Your Turn

Sort it!

Write each term from the pool into the correct box below. Each term belongs to exactly one box.

Carbon-14 Iodine-131 Cobalt-60 Constant for an isotope Time for half to decay Uranium-238 Measured in seconds, days or years Radon-222 Halving each time interval Activity falls over time

Radioactive isotopes

Facts about half-life

Show What You Know

1. A sample starts with 160 g of a radioactive isotope. Its half-life is 1 day. Complete the table to show the mass remaining each day. Remember, the mass halves each half-life.

Recall 2 marks

Time (days)	Number of half-lives	Mass remaining (g)
0	0	160
1	1
2	2
3	3
4	4

2. In your own words, write a sentence explaining what the half-life of an isotope tells you.

Recall 2 marks

Wrap Up

In one sentence, explain why the half-life of an isotope does not change even if you start with a bigger sample.