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Particle model of matter (The particle model and motion of gases (The 3…
Particle model of matter
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Density of materials
The density of an object depends on what it's made of and arrangement of particles. A dense material has particles packed tightly together. Particles in a less dense material more spread out- compressing it would make it more dense (would not change mass but decrease volume). Solids are generally denser than liquids. Gases are less dense than liquids.
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Specific latent heat
When a substance is melting or boiling, energy is being put in so increases internal energy. But energy is being used for breaking intermolecular forces rather than raising temperature. There are flat spots on the heating graph where energy is being transferred by heating but not being used to raise the temperature.
When a substance is condensing or freezing, bonds are forming between particles; releases energy. The internal energy decreases, but the temperature doesn't go down until all substances condense or freeze. The flat parts on the graph show this energy transfer.
Latent heat- energy needed to change the state of a substance. Specific latent heat- amount of energy needed to change 1kg of a substance from one state to another without changing its temperature.
For cooling, SLH is energy released by a change in state. SLH is different for different materials, and for changing between different states.
SLH of fusion- SLH for changing between a solid and liquid. SLH of vaporisation- SLH for changing between a liquid and gas.