C2 - The Three States of Matter

What are the three common states of matter?

Solid, liquid, and gas.

How are particles arranged in a solid?

In a regular pattern, packed closely together with almost no spaces.

Why are solids hard to compress?

Because particles are packed together with almost no spaces.

Why do solids have a fixed shape?

Particles in a solid can only vibrate and cannot move from place to place.

How are particles arranged in a liquid?

Close together with few spaces, but not in a fixed pattern.

Why are liquids hard to compress?

Because the particles are still close together with little space between them.

Why can liquids flow and take the shape of their container?

Because the particles can move around each other.

How are particles arranged in a gas?

Widely spaced and moving quickly and randomly.

Why are gases easy to compress?

Because the particles are far apart with lots of empty space.

Why do gases spread out to fill their container?

Because particles move quickly and randomly in all directions.

What is melting?

The change from a solid to a liquid at the melting point.

Why does melting require energy?

Energy is needed to break the forces of attraction between particles in a solid.

What is freezing?

The change from a liquid to a solid at the melting point.

What happens to forces during freezing?

The forces of attraction between particles reform.

What is boiling?

The change from a liquid to a gas at the boiling point.

Why does boiling require energy?

To break the forces of attraction between particles in a liquid.

What is condensing?

The change from a gas to a liquid at the boiling point.

What happens to forces during condensing?

The forces of attraction between particles reform.

What determines the melting and boiling point of a substance?

The strength of the forces of attraction between particles.

If forces between particles are weak, what happens to the melting and boiling points?

They are low because little energy is needed to break the forces.

If forces between particles are strong, what happens to the melting and boiling points?

They are high because a lot of energy is needed to break the forces.

Give an example of a substance with weak forces and low melting point.

Candle wax.

Give an example of a substance with strong forces and high melting point.

Sodium chloride (NaCl).

What are the limitations of the simple particle model (higher tier)?

It assumes particles are solid spheres and that there are no forces between particles.

Why is the assumption that particles are solid spheres a limitation?

Because real particles have different shapes and are not solid spheres.

Why is the assumption that there are no forces a limitation?

Because forces of attraction exist and they strongly affect melting and boiling points.