Section 5 Flashcards
Describe solids?
Strong forces of attraction hold the particles close together in a fixed regular arrangement. The particles don’t have much energy so they can only vibrate about their fixed positions.
Describe solids?
Weaker forces of attraction between particles. The particle are close together, but can move past each other, and form irregular arrangements. They have more energy than the particles in a solid - they move in random directions at low speeds.
Describe gases?
Almost no forces of attraction between the particles. The particles have more energy than those in liquids and solids - they are free to move, and travel in random directions and at high speeds.
What happens when you heat a liquid?
The heat energy makes the particles move faster.
What happens eventually when heating a liquid?
When the particles have enough energy to overcome their attraction to each other, big bubbles of gas form in the liquid - this is boiling.
What happens when you heat a solid?
Heat energy makes the particles vibrate faster until eventually the forces between them are overcome and the particles start to move around - this is melting.
What is evaporation?
When particles escape from a liquid and become gas particles.
When can particles evaporate?
At temperatures that are much lower than the liquid’s boiling point.
Why can particles near the surface escape and become gas particles?
- the particles are travelling in the right direction to escape the liquid.
- the particles are travelling fast enough to overcome the attractive forces of the other particles in the liquid.
Which particles are most likely to evaporate?
The fastest particles.
What happens when the fastest particles evaporate?
The average speed and kinetic energy of the remaining particles decreases.
What does the decrease in average particle energy mean?
The temperature of the remaining liquid falls - the liquid cools.
What is the cooling effect useful for?
When you sweat.
What is the average temperature of a gas in kelvins proportional to?
The average kinetic energy of its particles.
p1 / T1 =
p2 / T2
