Kinetic Theory

Stand a pan of crushed ice on a hot ring with a thermometer in it and watch the reading. It climbs to zero and then it stops. The ring is still glowing, the ice is visibly turning to water, joules are pouring in at hundreds every second, and the number on the thermometer refuses to move. It stays there for minutes. Only when the last sliver of ice has gone does the reading start to rise again, and later, at one hundred, it stalls a second time and stays stalled while the pan boils dry. Two flat stretches in one heating, and in both of them energy is arriving with nothing to show for it on the scale.

Nothing has gone missing. This lesson shows you where those joules went, and it hands you a way of reading any temperature against time graph as a story about particles: how far apart they are, how fast they move, and how tightly they are held to one another. You will compare the three states in one model, define specific heat capacity and put numbers into the equation that goes with it, learn why an impurity shifts a melting point, and finish by designing a cooling investigation of your own. One part of the topic belongs to the Extension Tier alone and is marked as such where it appears, so you will always know which paragraphs your own paper can ask you about.