CLASS 9 CHEMISTRY 

AIM To determine the melting point of ice 

MATERIALS REQUIRED
Ice cubes, filter paper, beaker, wire gauze, tripod stand, burner, thermometer, stirrer, clamp stand.

THEORY
Ice is the solid form of H₂0. Its melting point is 0 °C i.e., the forces of interaction between the molecules in the solid form of H₂0 can be broken down at 0 °C and solid H₂0 gets converted into liquid water.

PROCEDURE

1. Take some ice cubes. Dry them using the filter paper and put them quickly in a beaker.
2. Place the beaker on a wire gauze kept over a tripod stand.
3. Suspend a thermometer, into the ice cubes, with the help of a clamp stand.
   
4. Heat the ice cubes and stir continuously for uniform heating.
5. Note the temperature (t₁) when ice starts melting.
6. Heat continuously till ice melts completely. Note this temperature (t₂).
7. Record your observations in the table.

OBSERVATIONS
Observation Table

Mean value of temperatures =  t1+t22
Boiling point of water = ……………..°C.

RESULT
The melting point of ice =………… °C.

PRECAUTIONS

1. Ice should be dry before using for melting point determination.
2. The bulb of the thermometer should be dipped in ice and should be surrounded on all sides with ice.
3. Maintain a uniform temperature, by continuous stirring.
4. Temperature should be measured by keeping eyes in line with the level of mercury.

EXPERIMENT-2

AIM- To determine the boiling point of water.

MATERIALS REQUIRED
Distilled water, boiling tube, rubber cork with two bores, delivery tube, clamp stand, pieces of pumice stone/ porcelain pieces, beaker, thermometer, burner.

THEORY
H₂0 exists in three different physical states-solid ice, liquid water and water vapour. In the liquid state, the forces of interaction are less and therefore, water exists as a liquid at room temperature. The boiling point of water is 100 °C, i.e. the vapour pressure of water becomes equal to atmospheric pressure at 100 °C at sea level.

PROCEDURE

1. Take about 50 ml distilled water in a boiling tube, and add few pieces of pumice stone/porcelain to it.
2. Fix a cork with two bores in the mouth of the boiling tube and fix a thermometer in one bore and delivery tube in the other.
3. Clamp the tube to the stand.
   
4. Place a beaker below the open end of the delivery tube to collect condensed water.
5. Heat the boiling tube by preferably rotating the flame for uniform heating.
6. Note the temperature (t₁) when water starts boiling.
7. Heat continuously till the temperature becomes constant, and water keeps on boiling. Note this temperature (t₂)
8. Record your observations in the table.

OBSERVATIONS
Observation Table

Mean value of temperatures =  t1+t22
Boiling point of water = ……………..°C.

RESULT
The boiling poin of water = ……….. °C

PRECAUTIONS

1. Use distilled water only. Impure water and hard water have boiling point greater than 100°C.
2. The bulb of the thermometer should be slightly above the liquid.
3. Add porcelain pieces before heating to avoid bumping.
4. Heat water by rotating the flame.
5. Note the temperature by keeping the eyes in line with the level of mercury.