Topic 5 - States of Matter

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[edit] 5.1 States of matter

[edit] 5.1.1

Solids : Molecules/atoms tightly packed. Force of attraction between molecules overcomes any translational motion of molecules (they do, however, vibrate in position).

Liquids : Particles held close together, but not as strongly as solids in that they are free to move, but not to escape the liquid (except for fast travelling particles i.e. evaporation).

Gas : Particles move independently and randomly, with no significant forces between particles, and a large (comparatively) amount of space between them.

[edit] 5.1.2

Ideal gas : Composed of randomly moving point masses occupying no space and with no forces between masses. The average (rms) speed of the movement of particles is proportional to temperature (in K). As a result, the kinetic energy of the particles is also proportional to temperature.

    An ideal gas will follow the ideal gas law: PV=nRT.

[edit] 5.1.3

Solid -> liquid : The rigid structure of the solid is overcome due to increased vibration of particles (due to energy being added in the form of heat). The particles can not escape from the liquid, but can move within it.

Liquid -> gas : As energy (in the form of heat) is given to the liquid, the particles gain enough energy to escape the liquid, and become a gas, with particles widely spaced.

Gas -> liquid : As heat (energy) is removed, the particles slow down to the point where the forces between particles are strong enough to hold them together making a liquid (shock, horror!)

Liquid -> solid : Energy is removed, particles move slower, resulting in stronger forces and a more rigid structure.

[edit] 5.1.4

Increase in temp -> Larger volume or higher pressure.
Increase in volume -> Decrease in temp or decrease in pressure.
Increase in pressure -> Decrease in volume or increase in temp.
This is synthesized in the ideal gas law: PV = nRT.

[edit] 5.1.5

Since the particles are moving at random, two separated samples of gas will eventually mix causing diffusion. This will occur at a higher rate with higher temperature since the particles are moving faster.