1. Freezing….Boiling…. Sublimation…. Condensation……Evaporation
Changes in States
Freezing….Boiling….
Sublimation….
Condensation……Evaporation

2. Freezing
To explain the movement of particles in the process of _____________.
Freezing
 (a)   Freezing : ___________ state  __________
state.
freezing
liquid
solid
Liquid particles
Solid particles

3. Explanation using KPT drops until its freezing point is reached.
When a liquid is cooled, the temperature ________
until its freezing point is reached.
During freezing, the liquid particles will lose the
heat energy to the surroundings as they
____________ to take up ________
and________ positions in the solid.
Note: For all pure substances, the freezing point is the same as the melting point.
Slows down
fixed
orderly

4. Reading a Graph on Freezing
temperature remains constant
freezing completes
freezing starts
freezing point (=melting point)
SOLID
LIQUID + SOLID
LIQUID
temperature (ºC)
time from start (min)

5. Reading a graph on freezing
Graph shows how temperature of substance changes with time during
melting when it is heated steadily.
1. PQ the substance is completely ______________.
2. Point Q - ____________ begins at _________.
( The ______ drop of liquid begins to form a ______).
3. QR ________ continues to take place. The substance
exists as a ________ of _____ and __________.
4. Point R – The last drop of _________ will change into a ______
5. RS – The substance is completely __________
liquid
freezing
690C
solid
first
freezing
mixture
solid
liquid
liquid
solid
solid

6. Think……..
Why does the temperature remain constant between QR even though the substance is continuously cooled?
Ans:
During cooling heat is given out by particles as they take up fixed positions is equal to heat loss from the surround during cooling.

7. Sublimation
solid
It is a process where a _________ when heated changes directly into a ________ without going through a _________ state.
During sublimation, heat energy is _________ to _______________________.
Examples of substance that sublimes:
gas
liquid
absorbed
forces of attraction
Dry ice
Iodine (crystals to purple vapour)
Moth balls
Ammonium chloride, NH4Cl

8. Condensation
Gas
It is a process where a _________ is changed into a ______ or _______.
During condensation, heat energy is _________ to form back the _________________________.
solid
liquid
given out
forces of attraction

9. Evaporation
gas
It is a process where a _______ is changed into a ______ but it occurs _____ the boiling point of the liquid.
During evaporation, heat energy is ___________ to ____________________________.
liquid
below
absorbed
break the forces of attraction

10. Differences between evaporation and boiling
1. Occurs at the surface of liquid
1. Occurs in the whole liquid
2. Occurs over a range of temperature
2. Occur at fixed temperature e,g water boils at 100 degree celsius
3. No bubbles are formed
3. Bubbles are formed within
the liquid
Some liquids whose boiling points are not far from the room temperature tends to evaporate easily. Such liquid are called _________ liquids. E.g nail polish remover ; perfumes
volatile

11. Summary (2) (4) (3) (5) Melting ; Heat energy is _______

12. Predicting states Example: What would be the state of substance X
at room temperature given the mp is 400C
and bp is 1090C.
Ans: Everyone look on board!