Temperature, Pressure, and States of Matter

Your understanding of how particles behave is the key to mastering this topic. Brownian motion shows us that particles are constantly moving randomly - you can actually see this if you watch pollen grains jiggling about under a microscope because air molecules are constantly bumping into them.

Absolute zero $-273°C$ is the coldest possible temperature where particles would completely stop moving. We convert to Kelvin temperature by adding 273 to Celsius, and this scale directly relates to how much kinetic energy particles have - the higher the temperature in Kelvin, the faster they're moving.

When substances change state (solid to liquid to gas), they either absorb energy from their surroundings (like melting ice) or release energy (like water vapour condensing on a cold window). During these changes of state, temperature stays constant even though you're still adding heat - all that energy goes into breaking or forming bonds between particles.

Specific heat capacity tells you how much energy you need to heat up 1kg of a material by 1°C. Materials with high specific heat capacity (like water) take ages to heat up but also stay warm for longer, whilst materials with low specific heat capacity change temperature quickly.

Key Point: Gas pressure and temperature are directly proportional - double the temperature in Kelvin, and you double the pressure (if volume stays constant).