Melting point of ice and boiling point of water


Posted Date:     Total Responses: 0    Posted By: C.N.Anantharaman   Member Level: Gold   Points/Cash: 6   


Objective:-

(1)To determine the melting point of ice.

Materials required:-
Ice cubes,blotting paper,250 ml beakers,wire gauze,tripod stand,burner,thermometer,stirer,clamp stand,etc.

Theory:-
Ice is the solid state of water.For ice, the melting point is 0*C.

Melting point: The constant temperature at which a solid changes into a liquid is called melting point of the solid.The melting point of a solid is an indication of the strength of the force of attraction between its particles.

During melting,Seperation of molecules incrases by large amount.Whole of the supplied heat energy is consumed in increasing potential energy of the molecules.The kinetic energy does not increase further.The temperature does not increase so long as the melting continues.

The quantity of heat required to completely change 1 kg of ice into water without any change in temperature is known as the latent heat of fusion(melting) of ice.This amount of heat is 335-kJ

Procedure:-

Take some ice cubes or ice pieces.Dry them with filter paper and quickly put in a beaker.Place the beaker over a wire gauze kept over a tripod stand.Suspend a thermometer with the help of clamp stand so that its bulb remains in the middle of the ice cubes.The cubes are moderately heated by a gas burner and stirred continously to keep a uniform temperature throughout.Note the temperature(t2) of water when oce is completely melted.Record your observations in tabular form.Repeat the experiment three times.

Observations:-

Observation table

S.no Starts melting completely melted
(t1) (t2)

(1) 0*C 0*C

(2) 0*C 0*C

(3) 0*C 0*C

Mean value of t1+t2/2 = 0+0/2= 0/2=0

Melting point of ice is 0*C.
______

Inference:-


Melting point of ice is 0*C.
______
Precautions:-

(1)The bulb of the thermometer should be kept sorrounded with ice cubes.

(2)Ice should be stirred regularly to keep a uniform temperature throughout.

(3)Note the temperature by keeping your eyes in line with the level of mercury.

Objective:-
(2)To determine the boiling point of water.

Materials required:-

Distilled water,hard test tube(boiling testtube),rubber cork with two bores,delivery tube,iron stand with clamp,pieces of pumic stones,250 ml beaker,thermometer

Theory:-
When a liquid(such as water) is heated,its molecules gain energy and their kineti energy increases.On continuous heating a particular temperature is reached when these molecules leave the surface )in the form of vapour) to produce a pressure above the liquid equal to atmospheric pressure.At this stage,the temperature remains stationary(constant) even on heating fur5ther.The stationar6y temperature at which the pressure of the vapours leaving the surface of the liquid equals the atmospheric pressure is called the boiling point of a liquid.Due to the ionic bond,ionic compounds have higher boiling point than covalent compound.

(1)Most of the covalent compounds have low boiling points.

(2)Ionic compounds have high boiling points.

(3)Addition of salt in water rises its boiling point.

Procedure:-

(1)Take about 70 to 100 ml of fresh (distilled) water(not hard water,which contains extra salts) in a hard test tube and add 2-3 small pieces of pumice stone.

(2)Fix a cork with two bores in the mouth of the boiling tube and clamp it with the stand.

(3)Introduce a thermometer in one bore of the rubber cork of the boiling tube and a delivery tube in the second bore.Keep the bulb of the thermometer above about 3-5 cm from the surface of the water.

(4)Place the beaker below the second end of the delivery tube to collect the condensed water.

(5)Heat the tube gently, preferably by rotating the flame. Note the temperature when boiling of water starts.Continue to heat the water remains boiling.Note the constant temperature.

(6)Record your observations in tabular form.

(7)repeat the experiment three times.

Observations:-

(1)Record your observations in a table as given below:-

S.no of readings Starts boliling Continues to boil
t1 t2

(1) 100*C 100*C

(2) 100*C 100*C

(3) 100*C 100*C

Mean value of t1+t2/2=100+100/2 = 200/2 =100*C

i.e. The boiling point of water is 100*C

Inference:-

(1)The boiling point of water is 100*C

Precaution:-

(1)The bulb of the thermometer should be kept about 4-5 cm above the surface of the liquid(water).

(2)Pieces of pumice stone should be added to water before heating to avoid bumping.

(3)Heating of water should be done by rotating the flame.

(4)Note temperature by keeping your eyes in line with the level of mercury.




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