2.1.3

Changes of State

Test yourself

Changes of State

A material doesn’t stay as a certain state forever. Materials are continuously changing between all three states depending on temperature and pressure. This is known as a reversible physical change.

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Melting

  • Melting is a change from solid to liquid.
  • Melting happens when the solid particles get some extra energy, which makes them vibrate faster and faster until they have enough energy to break away from their fixed position.
  • Then the particles can move freely over each other, and have turned into liquid particles
  • Heating something will give solid particles enough energy for them to adopt a liquid particle arrangement.
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Boiling

  • Boiling is a change from liquid to gas.
  • Boiling happens when liquid particles are heated, making them move faster and faster.
  • Eventually, the liquid particles will be moving very quickly and in random directions, without being connected to any other particles – they have changed into the gas particle arrangement.
  • When you boil the kettle the steam that comes out the top is water vapour (water as a gas), because the liquid water has been heated up enough to boil.
  • Water boils at 100oC.
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Evaporation

  • Evaporation is also a change from liquid to gas.
  • The difference between evaporation and boiling is that evaporation can happen at any temperature.
  • When you get out the shower, the water on the doors eventually 'disappears' because it evaporates.
  • It doesn't boil, but it does turn into a gas.
  • This is because different particles in a liquid have different amounts of energy.
  • Some particles will gain enough energy to break free and will become a gas.
  • A liquid boils when every particle has this much energy.
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Condensation

  • Condensation is a change of state from a gas to liquid.
  • Condensation happens when you cool down a gas and reduce the energy of the particles.
  • The particles slow down and clump together, taking the arrangement of a liquid.
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Freezing

  • Freezing is when a liquid turns into a solid.
    • E.g. when water freezes to ice, which happens at 0oC.
  • To freeze a liquid, you have to cool it down, which makes the particles travel slower and slower until they are just vibrating in a fixed position and are all very close together.
  • The particles will then look like the particle arrangement in a solid and the substance has frozen.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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