A student uses ball bearings on a flat tray to model changes of state.

When the tray is shaken gently, the ball bearings vibrate in a regular pattern. This represents a solid.
When the tray is shaken harder, the ball bearings move past each other but stay close together. This represents a liquid.
When the tray is shaken very hard, the ball bearings fly apart and leave the tray. This represents a gas.

The table shows information about three substances.

Substance	Particles	Melting point ( $∘C^\circ\mathrm{C}$ )	Boiling point ( $∘C^\circ\mathrm{C}$ )
argon	single atoms, all the same size	−189	−186
water	molecules with a bent shape	0	100
sodium chloride	ions of two different sizes	801	1413

What does shaking the tray harder represent?

Evaluate how well the ball-bearing model explains the changes of state of these three substances.

Use the data in the table. Suggest how the model could be improved.

A student uses ball bearings on a flat tray to model changes of state.

When the tray is shaken gently, the ball bearings vibrate in a regular pattern. This represents a solid.
When the tray is shaken harder, the ball bearings move past each other but stay close together. This represents a liquid.
When the tray is shaken very hard, the ball bearings fly apart and leave the tray. This represents a gas.

The table shows information about three substances.

Substance	Particles	Melting point ( $∘C^\circ\mathrm{C}$ )	Boiling point ( $∘C^\circ\mathrm{C}$ )
argon	single atoms, all the same size	−189	−186
water	molecules with a bent shape	0	100
sodium chloride	ions of two different sizes	801	1413

What does shaking the tray harder represent?

Evaluate how well the ball-bearing model explains the changes of state of these three substances.

Use the data in the table. Suggest how the model could be improved.

1.1 The particle model

1.1 The particle model Questions