| All particles on Earth have kinetic energy. But scientists have calculated that there might be places in deep space where there is no energy in particles. This theoretical temperature is called absolute zero on the Kelvin scale and it would be equivalent to -273.15°C.
Scientists have come close, but have never achieved, absolute zero on Earth.
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Textbook Readings
Science in Action 7
pages 190 to 197
or
Science Focus 7
pages 202 to 203
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Solids have a definite shape and volume. Volume is the amount of space matter occupies. Did your dresser or bed change shape over night? If we to closely examine the particles in a solid we would find that there are powerful attractive forces between the particles so their movement is movement in place. They move back and forth in a fixed position.
Liquids have a definite volume but no definite shape. They take the shape of the container their in. A closer examination at the particle level would reveal that there is more kinetic energy in the particles, and larger spaces between them. This allows the particles to slip by one another, but attractive forces still keep them together. This allows liquids to flow.
Gases have no fixed volume or shape. They will fill the container they are in. The kinetic energy of the particles overcomes the attractive forces between the particles and the gas particles fly of in all directions. Their bouncing and bumping into each other and the container walls keeps them apart. Only the container they are in keeps them from flying away.
It is important to note that different kinds of matter need different amounts of energy to make them change state. For example, Oxygen is a gas at room temperature while water is a liquid and various metals solid. Look around the room you are in and think of the states of matter in the room. You can easily see the solids and the liquids but detecting gases is more difficult. The air in your room contains gases like nitrogen, oxygen, carbon dioxide and even water vapour. During the winter the air in your room touches cold windows and the water in the air will change state into liquid water and even solid water in the form of frost.
Summary
The particle model states:
1. All matter is made up of extremely small particles.
2. These tiny particles are always moving.
3. Adding heat to the particles makes them move faster.
4. The particles have spaces between them.
5. There are attractive forces between the particles.
All matter can be classified as solid, liquid or gas, and there can be a change of state by adding or taking energy away.
Changes of State Diagram
There are many terms used to scientifically describe the states that matter undergoes as it gains and loses energy.
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