When you compress something you are pushing it into a smaller space. When something contracts, it gets smaller.
Compression is the action or state of being squished down or made smaller or more pressed together. One example is a pile of material is squished together and made smaller and denser.
Contraction on the other hand is the act of decreasing (something) in size or volume or quantity or scope; it usually involves muscles and words.
As the average energy of particles decreases, the spaces between the particles decreases. They contract (decrease their volume) as the temperature decreases. Pure substances are matter that are made up of only one kind of particle, which can be a solid liquid or a gas.
These phases, or states have very specific properties in relation to the particle model.
Science Focus Topic 4 Notes: Expansion & Contraction via kwout
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