Year 7 Science · Unit 2 · Lesson 1

What Is Matter?

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Learning Goals

Warm Up

Sort it!

Write each item from the pool into the correct category box. Remember: a solid has a fixed shape AND fixed volume; a liquid has a fixed volume but takes the shape of its container; a gas has neither.

helium in a balloon eucalyptus oil a steel ruler steam from a kettle milk a grain of sand smoke from a candle honey

Solid

Liquid

Gas

Your Turn

Real-world context

In 2023, the Australian Navy conducted deep-sea diving exercises off the coast of Western Australia. Divers used rigid diving bells — sealed chambers lowered to depths of around 200 m. Engineers must carefully calculate the amount of breathing gas (a mix of oxygen and helium) stored inside the bell, because the gas will compress under pressure. The liquid water surrounding the bell, however, does not compress at all, even at 200 m.

(a) Using what you know about the shape and volume properties of gases and liquids, explain why the breathing gas inside the diving bell can be compressed but the liquid water outside cannot.

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(b) Both the gas and the liquid water inside the diving bell are matter. Give one piece of evidence for each that confirms it has mass and takes up space.

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Show What You Know

1. An astronaut has a mass of 75 kg on Earth. State (a) their mass on the Moon and (b) whether their weight on the Moon would be the same, more, or less than on Earth. Justify both answers using the definitions of mass and weight from the lesson.

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2. A student says "heat is matter because you can feel it." Use the two-part test for matter (mass AND volume) to explain why heat is NOT matter.

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Wrap Up

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

HSCScience · Year 7 Science · Unit 2 · Lesson 1 · Apply Worksheet