Lesson 4.2 - Changing State

Changes of state

There are 4 main changes of state:

• Melting

• Boiling

• Freezing

• Condensing

There are two, less common state changes:

• Sublimation

• Deposition

Melting

Melting is where a solid turns into a liquid.

solid -> liquid

The substance gains energy.

The bonds are weakened slightly.

Boiling

Boiling is where a liquid turns into a gas.

liquid -> gas

The substance gains energy.

The bonds are weakened more.

Freezing

Freezing is where a liquid turns into a solid.

liquid -> solid

The substance loses energy.

The bonds are strengthened.

Condensing

Condensing (or 'condensation') is where a gas turns into a liquid.

gas -> liquid

The substance loses energy.

The bonds are strengthened slightly.

Sublimation

During sublimation, a solid directly turns into a gas.

solid -> gas

The substance does not turn into a liquid in between.

Sublimation

Deposition is where a gas directly turns into a solid.

gas -> solid

The substance does not turn into a liquid in between.

Melting point

The melting point is the point at which a substance melts or freezes.

A substance melts when its temperature is higher than its melting point.

A substance freezes when its temperature is lower than its melting point.

Boiling point

The boiling point is the point at which a substance boils or condenses.

A substance boils when its temperature is higher than its boiling point.

A substance condenses when its temperature is lower than its boiling point.

Summary

State change	From	To	Energy is...	Bonds are...
Melting	Solid	Liquid	Gained	Weakened
Boiling	Liquid	Gas	Gained	Weakened
Freezing	Liquid	Liquid	Lost	Strengthened
Boiling	Liquid	Gas	Lost	Strengthened
Freezing	Solid	Gas	Gained	Weakened
Deposition	Gas	Liquid	Lost	Strengthened