Tpm

At the end of the lesson, students should be able to:

define melting and freezing.

define boiling and condensation

ObjectivesObjectivesObjectivesObjectives

interpret the heating curve

Internal energyInternal energyInternal energyInternal energy

The internal energy of a body is the combination of the total kinetic energy (due to molecular motion) and potential energy (due to inter-molecular forces) of the molecules in the body.

An increase in temperature leads to an increasein the kinetic component of the internal energy.

When the temperature increases, the molecule move faster

Melting is a process in which a substance changes its state from solid to liquid..

Solid Liquid

Melting and FreezingMelting and FreezingMelting and FreezingMelting and Freezing

The temperature at which this happens is called the melting point of the substance.

Freezing is a process in which a substance changes its state from liquid to solid.

Solid Liquid

Melting and FreezingMelting and FreezingMelting and FreezingMelting and Freezing

Solid Liquid

The temperature at which this happens is called the freezing point of the

substance.Melting point = Freezing point

Boiling is the process in which a substance changes from the liquid state to the gaseous

state.

Liquid Gas

Boiling and CondensationBoiling and CondensationBoiling and CondensationBoiling and Condensation

Liquid Gas

The temperature at which this happens is called the boiling point of the substance.

Condensation is a process in which a substance changes from the gaseous state to the liquid

state.

The temperature at which this happens is called the condensation point of the substance.

Boiling and CondensationBoiling and CondensationBoiling and CondensationBoiling and Condensation

the condensation point of the substance.

Boiling point = Condensation point

boiling point

gaseousstate

State of matterState of matterState of matterState of matter

melting point

solidstate

liquidstate

Change of StateChange of StateChange of StateChange of State

solid liquid gas

melting /freezing point

boiling /condensation point

During the change of state(freezing/melting/boiling/condensation), the temperature of the substance remains constant.

Take note!

For example, when pure ice is melting at 0 °C, For example, when pure ice is melting at 0 °C, it will remain at 0 °C until all the ice has melted. The temperature of pure water will increasebeyond 0 °C, when more thermal energy is added to the water.

Heating curveHeating curveHeating curveHeating curveTemperature / °°°°C

This is a Temperature time graph.In this example, water is being heated from -10 °C

0

-10 Heat supplied →iceTime / s

heated from -10 °CAs you can see, the temperature of water rises to -10 °C.

Heating curveHeating curveHeating curveHeating curveTemperature / °°°°C

When the temperature of water reaches 0 °C, the ice melts. During the change in state, there is no change in temperature even though thermal energy is still being

0

-10 Heat supplied →

ice → liquid

ice(melting) Time / s

thermal energy is still being transferred to the water.

100

Heating curveHeating curveHeating curveHeating curveTemperature / °°°°C

After all the ice has melted, water will

0

-10 Heat supplied →

ice → liquid

liquid

ice(melting) Time / s

Change in state, no change in temperature

melted, water will continue to increase in temperature

100 liquid → steam(boiling)

Heating curveHeating curveHeating curveHeating curveTemperature / °°°°C

Change in state, no change in temperature

0

-10 Heat supplied →

ice → liquid

liquid

ice(melting) Time / s

Change in state, no change in temperature

120

100 liquid → steam(boiling)

steam

Heating curveHeating curveHeating curveHeating curveTemperature / °°°°C

Change in state, no change in temperature

0

-10 Heat supplied →

ice → liquid

liquid

ice(melting) Time / s

Change in state, no change in temperature

120 °C

100 °C steam → liquid(condensation)

steam

liquid

Cooling curveCooling curveCooling curveCooling curve

0 °C

-10 °C

Heat removed →

liquid → ice

liquid

ice(freezing)