GCSE Chemistry (AQA)

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Energy & State Changes

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Bonding, structure, and the properties of matter How bonding and structure are related to the properties of substances

Energy & State Changes

3:32 Changes of State
Spec 4.2.2.1
Previous Bulk Properties & Particles Next Conservation of Energy
  • Substances in solid, liquid, or gas states have forces of attraction holding particles together.
  • Changes in state occur when these forces are overcome.
  • Heating a solid transfers energy to particles, overcoming some forces and causing it to melt into a liquid.
  • In a liquid, particles move and flow over each other.
  • Continued heating of a liquid overcomes remaining forces, causing it to boil and change to a gas.
  • Cooling a substance transfers energy from particles to surroundings, strengthening forces and changing state.
  • Cooling a gas reforms forces, turning it into a liquid, and further cooling turns it into a solid.
  • The energy required for a state change depends on the strength of forces between particles.
  • Stronger forces require more energy to overcome.
  • Water has weak forces, resulting in low melting and boiling points.
  • Diamond has strong forces, resulting in high melting and boiling points.

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