Page 140 - Physics - XI

Activities
Activities

ACTIVITY - 1

Aim
To observe change of state and plot a cooling curve for molten wax.

Apparatus and Materials Required

A hard glass test tube, a cork having two holes, a thermometer, wire gauze, a stirrer, burner, stand, wax,water,
beaker, tripod stand, clamp stand, and stopwatch
Stirrer
Principle/Theory Thermometer

There are three states of matter namely solid, liquid, and gas. While Cork
heating a solid, it changes into liquid state and its temperature increases.
The process of conversion of a solid into a liquid state is known as Test tube
fusion or melting. The temperature at which melting takes place is
called melting point. During the process of melting, the temperature
of the solid-liquid remains constant till the whole of the solid changes Water
into liquid. On cooling a liquid, it freezes to a solid state at the same Beaker
temperature as its melting point. Wax
We can fi nd the melting point of wax by plotting a cooling curve. Wire
gauze
Procedure Burner

1. Note the least count and range of the thermometer.
2. Fill about two third of the test tube with the molten wax. Put a
thermometer and stirrer in it. Pass the thermometer and stirrer
through the cork. Check that thermometer should not touch the Fig. 1.1: Apparatus for cooling
curve for molten wax

sides of the test tube.
3. Fix the test tube in a clamp stand and suspend it in water bath heated by a burner. Let the whole of wax
melt and its temperature is about 10°C above its melting point.

4. Now, turn off the burner and allow the water and wax to cool. Go on stirring the molten wax and note
the temperature after every half minute. Keep on stirring as long as it is possible.
5. Continue cooling and record the temperature till whole of wax has solidifi ed.

6. Note all the observations in the observation table.

Observations
Least count of the thermometer = ______ °C

Range of the thermometer = ______ °C to ______ °C

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