Particles and states of matter · Grade 10
In Grade 10 you learn: internal energy.
All matter is made of tiny particles that are always moving. How closely they are packed and how freely they move explains the properties of solids, liquids and gases, why gases can be squashed, why smells spread, and what really happens when things melt or boil.
Key facts
- Solid: particles close together in a regular pattern, vibrating about fixed positions.
- Liquid: particles close together but randomly arranged, sliding past each other.
- Gas: particles far apart, moving quickly and randomly.
- Diffusion: particles spread from where there are many to where there are fewer; faster when hotter.
- Internal energy = total kinetic + potential energy of the particles.
- Heating raises the temperature (more kinetic energy) or changes the state (more potential energy).
Worked examples
Example 1
Why can a gas be compressed but a liquid cannot?
Answer: gas particles have large gaps between them; liquid particles are already touching
Example 2
Use the particle model to explain why the temperature stays at 0°C while ice melts.
Answer: the energy weakens the bonds (raises potential energy) instead of speeding particles up
Example 3
Describe how the particles are arranged and how they move in a solid, a liquid and a gas.
Answer: solid: close together in a regular pattern, vibrating in place; liquid: close together but random, sliding past each other; gas: far apart, moving quickly in all directions
Example 4
A drop of ink is put into a beaker of water and left alone. What happens? Why does it happen faster in hot water?
Answer: the ink slowly spreads through all the water (diffusion); in hot water the particles move faster, so it spreads faster
Example 5
What happens to the particles of ice when it melts?
Answer: they gain energy, vibrate more, and break out of their fixed pattern, so they can slide past each other; they stay close together