Basic Chemistry/Physical changes

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Physical changes don't change the particles themselves - only their arrangement or their energy.

Changes of state[edit]

This is changing from one state of matter to another.

Gas pressure[edit]

Gas pressure is due to particles hitting a surface.

  • When you increase the temperature, it makes particles move faster. This has two effects:
    • The particles hit the surfaces harder, and
    • more often.
  • This increases the pressure.
  • When you reduce the volume of the container in which the gas is contained, the pressures also increases. This is because the particles become more squashed up in a smaller space, so they hit the surfaces more often.

Diffusion[edit]

Diffusion is particles spreading out. Also, Diffusion is the movement of particles from a lower point of concentration to a higher point of concentration

NOTE: temperature is a major determinant of how fast a particle diffuse. Particles in a solid state don't diffuse

  • It's typically slow, for example a smell spreading slowly across a room.
  • The smell particles move away from where there are lots of them towards areas where there's only a few of them.
  • It's slow because there are also lots of air particles getting in the way of the smell particles.

Dissolving[edit]

When a solid dissolves in a liquid it seems to disappear into it,If it is a colored substance it may color the liquid.

However it does not disappear its particles simply separate and spread out through the liquid. This is possible because the liquid has gaps between its particles and it is into them that the particles of the dissolving substance pass.