Changes Of State

Monday, September 22 08

Meherzad Bhathena

Changes of State Solid • • •

fixed shape fixed volume strong forces between particles

This occurs because the particles are in a fixed lattice. So they cannot rearrange their shape. The particles in

Liquid • • •

variable shape fixed volume medium forces between particles

When heat is added to a substance, the particles move faster. Eventually, they move so fast that they break the lattice bonds and can flow as a liquid. This change of state is called melting. Melting is the breakdown of order.

Gas • • •

Variable shape Variable volume Very weak interaction between particles

If you continue to add heat, the particles will move so fast they evaporate. The molecules then break free of the substance and become a gas. This change of state is called evaporation.

Plasma • • •

Variable shape Variable volume Electrons leave atoms

Monday, September 22 08 •

Meherzad Bhathena

Particles are charged

Changes of State As heat is added to substances, the substances change state Solid > Liquid (melting) Liquid > Gas (evaporation)

Some substances can even go straight from solid to gas Solid > Gas (sublimation)

As heat is removed to a substance, Gas > Liquid (condensation) Liquid > Solid (freezing) How does the temperature versus time graph look? As heat is added, the substance temperature rises. At the melting point, the heat gets used up breaking the bonds. While the heat is being used to break the bonds, the temperature stays constant.

The temperature beings to rise again after the change in state. The temperature stop rising again at boiling point. The temperature can then rise again.