1

Changes In States

2

Melting To explain the movement of particles in the process of _____________.

 Melting

 (a)   Melting: ___________ state __________

state.

 

melting

solid liquid

solid liquid

3

Explanation using KPT

When a solid is heated, the solid particles will ________ the heat and gain ________ to ___________ more vigorously.

When enough heat is applied, the solid particles vibrates so vigorously that they are able to ___________ the_______________________ holding the solid particles.

When this happen, the solid has turned into a _________; ________ has taken place.

energy

vibrate

melting

overcome

absorb

liquid

forces of attraction

4

Reading a Melting CurveNote: This curve is only true for a pure compound An experiment can be carried out and the result of the melting can be plotted as

shown:

Temperature (ºC)

Melting starts

Temperature remains constant

Melting completes

Time from start (min)

Melting point (69°C)

SOLID

SOLID + LIQUID

LIQUID

A

BC D

5

Reading the melting curveGraph shows how temperature of substance changes with time

during

melting when it is heated steadily.

 

1. AB - the substance is completely ______________.

2. Point B - ____________ begins at _________.

( The first drop of ________ appears).

3. BC - ________ continues to take place. The substance

exists as a ________ of _____ and __________.

4. Point C – The last drop of _________ is formed.

5. CD – The substance is completely __________

( ) 

690Cmelting

solid liquid

liquid

molten

liquid

liquid

mixture

solid

melting

6

Think……Why does the temperature remain constant between B and C even though heat is continuously supplied?

Ans: The heat is used to overcome the forces of attraction holding the solid particles instead of causing the temperature to rise.

7

Boiling To explain the movement of particles in the process of _____________.

Boiling

 (a)   Melting: ___________ state __________

state.

 

boiling

liquid gaseous

liquid gaseous

8

Explanation using KPT When a liquid is heated, the liquid particles will ________ the heat and gain ________ to ___________ more vigorously.

When enough heat is applied, the liquid particles vibrates so vigorously that they are able to ___________ the_______________________ holding the liquid particles.

When this happen, the liquid has turned into a _________; ________ has taken place.

absorbenerg

y vibrate

overcomeforces of

attraction gasboiling

9

Reading a Boiling CurveNote: This curve is only true for a pure compound An experiment can be carried out and the result of the melting can be plotted as

shown:

temperature (ºC)

time from start (min)

X Y

0

74ºC

W

10

Reading the boiling curveGraph shows how temperature of substance changes with time

during

melting when it is heated steadily.

 

1. WX - the substance is completely ______________.

2. Point X - ____________ begins at _________.

( The first drop of ________ appears).

3. XY - ________ continues to take place. The substance

exists as a ________ of _____ and __________.

4. Point Y – The last drop of ________change into

_________ state.

5. Beyond Y – The substance is completely __________

liquid

boiling 740Cgas

boilingmixture gas liquid

liquidgaseous

gaseous

11

Exercise: Combination of melting &

boiling curve

Time from start / min

Tempt / 0C

40

60

120

completely solid

completely liquid

completely gas

Mixture of solid & liquid

Mixture of liquid & gas

melting point, 60oC

boiling point, 120oC