Year 8 Science · Unit 2 · Lesson 08

Isotopes

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Learning Goals

Warm Up

Real-world scenario

Read the context carefully, then answer both questions using what you know about isotopes.

Real-world context

In 1991, a frozen mummy nicknamed Ötzi the Iceman was discovered in the Alps between Austria and Italy. Scientists used carbon-14 dating to determine he lived approximately 3,300 BCE, making him around 5,300 years old. When Ötzi was alive, his body absorbed carbon-14 from his food. After death, the carbon-14 slowly decayed at a predictable rate, allowing scientists to calculate how long ago he died.

(a) Explain why carbon-14 dating works. What specific property of isotopes makes it a reliable tool for determining the age of organic remains?

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(b) Carbon-14 dating is reliable up to about 50,000 years. Why can't it be used to date a fossil that is 200 million years old?

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Your Turn

Because… chain

Fill in the missing steps. Each event in the chain leads to the next. Given steps are shaded, complete the blank steps.

A patient is injected with technetium-99m, a radioactive isotope, into their bloodstream.
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The technetium-99m travels through the blood and concentrates in bone tissue.
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A scanner detects the gamma rays emitted by the isotope and maps where it has gathered.
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The resulting image shows areas of high and low isotope uptake across the skeleton.
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Overall outcome:

Show What You Know

1. Carbon-12 and carbon-14 are both carbon atoms. Explain how they are the same and how they are different. Use the terms atomic number, mass number, and neutron number in your answer.

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2. Why do isotopes of the same element behave almost identically in chemical reactions, even though they have different mass numbers?

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 8 Science · Unit 2 · Lesson 08 · Apply Worksheet