Topic 5 - Changes of State (Paper 2) Flashcards
what are the three states of matter?
solid, liquid, gas
how are particles arranged in a solid?
strong forces of attraction hold the particles together in a fixed, regular arrangement. particles don’t have much energy so can only vibrate about their fixed positions
how are particles arranged in a liquid?
weaker forces of attraction between the particles. the particles are close together but can move past each other and form irregular arrangements. they have more energy than particles in a solid and move in random directions at low speeds.
how are particles arranged in a gas?
almost no forces of attraction between the particles. particles have more energy than in liquids and solids. they are free to move and travel in random directions and at high speeds.
what is the thermal energy store?
the energy in a substances thermal energy store, held by its particles in their kinetic energy store.
what happens when you heat a liquid?
extra energy is transferred to the particles’ kinetic energy stores, making them move faster. eventually, the particles have enough energy to overcome their attraction to each other and bubbles of gas form.
what happens when you heat a solid?
extra energy makes the particles vibrate faster until eventually the forces between them are partly overcome.
why does a substance stay at a constant temperature when melting/boiling?
energy being put in is used for breaking bonds between particles rather than raising the temperature.
why does a substance stay at a constant temperature when condensing/freezing?
bonds are forming between particles, which releases energy. so the temperature doesn’t go down until all of the substance has changed state.
what is evaporation?
when particles escape from a liquid and become gas particles. this can happen at temperatures much lower than the liquids boiling point.
when can liquid particles evaporate?
if they are travelling in the right direction to escape the liquid and if they are travelling fast enough to overcome the attractive forces of the other particles in the liquid
why does the liquid cool when evaporation happens?
the fastest particles evaporate from the liquid. when they do, the average speed and energy in the kinetic energy stores of the remaining particles decreases, decreasing the average particle energy.
