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.

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

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.