IB Chemistry/States of Matter

5.1 States of matter

5.1.1 Solids

In a solid-state molecules/atoms are tightly packed. The force of attraction between molecules/atoms overcomes any translational motion of molecules (they do, however, vibrate in position).

5.1.2 Liquids

Liquids are particles that are 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 traveling particles -> evaporation).

5.1.3 Gas

Gas consists of particles that can move independently and randomly, with no significant forces between particles, and a large (comparatively) amount of space between them. An ideal gas is 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.

5.1.4 Transitions

Solid into 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 cannot escape from the liquid, but can move within it (thus dissolving in it). Liquid to 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 can take tremendous volumes. Gas into 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, a liquid is formed! Liquid into solid, even more energy is removed and particles move slower. Stronger forces build a more rigid structure for the material.

5.1.5 Increasing the temperature

Causes the material to become larger in volume or higher pressure. An increase in volume (which holds the material) will translate itself in a decrease in temperature or a decrease in pressure. An increase in pressure(on the other hand) will cause a decrease in volume or increase in temperature.

5.1.6 Diffusion

Since the particles are moving at random (here: in a gas), 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.