Page 29 - 新思维科学学生用书7 样章

2 Materials and their structure

Questions

1 What are the three states of matter?
2 Which state of matter can be compressed (squashed) easily?
3 Which state of matter cannot be poured?
4 List the properties of solids.

5 Name a property of liquids that they do not share with solids.
6 Name a property of gases that they share with liquids.
7 Name a property of gases that they do not share with solids or liquids.

Scientists look at what matter does

Scientists try to explain what they see. Here are some examples of how matter behaves that scientists
have tried to explain.

• You can smell food cooking in another room.
• Some substances get bigger when you heat them.
• Liquids, such as water, change to a gas when you heat them.

• Substances change from liquid to solid if you cool them.
Scientists think about why these things happen and try to come up with ideas to explain it. They form
a hypothesis, which is a suggestion for an explanation. This hypothesis can then be tested by carrying
out more investigations.

When a hypothesis has been tested and widely accepted as valid by other scientists, it is called a
theory.

The best theory to explain how matter behaves uses the idea of particles. Particles are tiny portions of

matter. This theory says that all matter is made up of tiny particles arranged in different ways.

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