1. Is the process by which the substance changes from solid to liquid.
Phase Change:
Is a change from one state (solid or liquid or gas) to another without a change in chemical composition.
Heat
Example:
H2O (s)
H2O (l)
Melting:
Is the process by which the substance
changes from solid to liquid.
The temperature at which this process occurs is called melting point.
Melting point (H2O) =
0oC

2. Is the process by which the substance changes from liquid to solid.
- Heat
H2O (l)
H2O (s)
Freezing:
Is the process by which the substance
changes from liquid to solid.
The temperature at which this process occurs is called freezing point.
Freezing point (H2O) =
0oC
Melting point = Freezing point
Solid Liquid
Melting
Freezing

3. Is the process by which the substance changes from liquid to gas.
Heat
H2O (l)
H2O (g)
Boiling:
Is the process by which the substance
changes from liquid to gas.
The temperature at which this process occurs is called boiling point.
Boiling point (H2O) =
100oC
Condensation:
Is the process by which the
substance changes from gas to liquid.

4. Boiling point = Condensation point
Liquid Gas
Boiling
Condensation
Boiling point = Condensation point
Ex: For water both are100oC.
(Liquid water boils at 100oC and
steam condenses at 100oC).

5. Is the process by which the substance changes from solid to gas.
Phase Changes:
Sublimation:
Is the process by which
the substance changes
from solid to gas.
Deposition:
Is the process by which the
substance changes from
gas to solid.

6. Sublimation point = Deposition point
Solid Gas
Sublimation
Deposition
Sublimation point = Deposition point
Ex: For CO2 both are-78oC.
(Solid CO2 sublimes at -78oC and
gas CO2 deposits at -78oC).

7. Melting Boiling Sublimation
Phase Changes:
Melting
Boiling
Sublimation
Absorb energy (endothermic processes)
Freezing
Condensation
Deposition
Release energy
(exothermic processes)

8. Gas Liquid Solid Sublimation Condensation Deposition Vaporization
Melting
Solid
Liquid
Freezing

9. Heating Curve of Water:
A – B -----
Kinetic
(Temperature increases)
Thermal Energy
Is converted
into
Temperature
B – C -----
Potential
(Temp. doesn’t change)
Phase
change
C – D -----
Kinetic
D – E -----
Potential
(Temp. doesn’t change)
E – F -----
Kinetic F
Vapor
Boiling
Point
Vaporization (Boiling) D E
Liquid
Melting
Point
Liquid & Vapor B
Melting C
Solid &
Liquid
Solid A 20
100
200
740
Heat Added (kcal)

10. Vaporization Boiling Evaporation
The conversion occurs in the entire mass of a liquid, this process require more thermal energy than evaporation.
When the conversion occurs at the surface of a liquid at room temperature.

11. evaporation is a cooling process.
As evaporation occurs, the particles with the highest kinetic energy tend to escape first.
As evaporation takes place, the liquid’s temperature decreases because the particles take the energy from its surrounding to become to gas, then
evaporation is a cooling process.

12. You can observe the effects of evaporative cooling on hot days.
When you perspire, water molecules in your perspiration absorb heat from your body and evaporate from the skin’s surface.
This evaporation leaves the remaining perspiration cooler.
* The perspiration that remains cools you further by absorbing more body heat.