3.5.2

Changes of State

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Changes of State

Changes of state are examples of a physical reaction.

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Changes of state

  • A change of state is a physical reaction.
  • The mass at the start and end does not change.
  • Changes of state happen when there is an increase or decrease in energy.
  • A change of state happens between solids, liquids, and gases.
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Internal energy

  • The energy a substance has is known as its internal energy.
    • Gases have the most internal energy.
    • Solids have the least internal energy.
  • If you heat a substance, it will increase the amount of internal energy.
  • If you cool a substance it will decrease the amount of internal energy.
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Examples of changes of state

  • Melting: Solids to Liquids → increase in internal energy.
  • Freezing: Liquids to Solids → decrease in internal energy.
  • Evaporation: Liquids to Gases → increase in internal energy.
  • Condensation: Gases to Liquids → decrease in internal energy.
  • Sublimation: Solids to Gases → increase in internal energy.
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Reversible reactions

  • Physical reactions are reversible.
  • A reversible physical reaction is when there is a change of state and it changes back again.
    • Water will evaporate in a hot shower room.
    • The water vapour will then turn back to liquid on a cold mirror. This is condensation.

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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