AQA GCSE Combined Science Physics - Particle Model Of Matter

What are the three states of matter?

Solid, liquid, gas.

How are particles arranged in a solid?

Closely packed in a fixed arrangement — vibrate in place.

How are particles arranged in a liquid?

Close together but can move past each other — irregular arrangement.

How are particles arranged in a gas?

Far apart, move randomly and quickly — low density.

What is density?

Mass per unit volume — how much matter is packed into a space.

What affects the density of an object?

Its mass and volume — more particles in a smaller space = higher density.

Why are solids usually denser than gases?

Their particles are tightly packed.

What happens to mass when a substance changes state?

It stays the same — mass is conserved.

What happens to internal energy when you heat a substance?

It increases — particles move faster or break bonds.

What is internal energy?

The total energy of particles — includes kinetic and potential energy.

What happens to temperature during a change of state?

It stays constant while bonds are being made or broken.

What is melting?

Changing from solid to liquid.

What is boiling/evaporating?

Changing from liquid to gas.

What is condensing?

Changing from gas to liquid.

What is freezing?

Changing from liquid to solid.

What is specific latent heat?

The energy needed to change the state of 1 kg of a substance without changing its temperature.

What is the specific latent heat of fusion?

Energy needed to melt or freeze 1 kg of a substance.

What is the specific latent heat of vaporisation?

Energy needed to boil or condense 1 kg of a substance.

What causes gas pressure?

Collisions of gas particles with the walls of their container.

What happens to gas pressure if volume decreases (at constant temperature)?

Pressure increases — particles collide more often.

What happens to pressure if temperature increases (in a fixed volume)?

Pressure increases — particles move faster and hit walls harder and more often.

What is the relationship between pressure and volume in gases?

Inversely proportional — as volume goes up, pressure goes down (if temp is constant).

Why do gases heat up when compressed quickly?

Work is done on the gas, increasing internal energy and temperature.

Why is it important to store gases in strong containers?

To withstand high pressure and avoid explosions.

How can we reduce gas pressure in a container?

Increase the volume or lower the temperature.