Page 141 - Physics - XI

Room temperature = ______ °C

Least count of stopwatch = ______ s

Table for cooling curve of molten wax

S. No. Time (minute) Temperature (°C)
1.
2.

3.
4.

5.

Graph and Calculations
Plot a graph between time and temperature of the wax, taking time on X-axis and temperature on Y-axis.

From the graph, fi nd the temperature (T) corresponding to fl at portion BC of the graph. This gives the
melting point of the molten wax.

Result Y
1. The cooling curve of molten wax is shown in Fig. 1.2. A

2. From the cooling curve, the melting point of the wax is Scale use on
X-axis: 1 cm = ....min.
______°C. Y-axis: 1 cm =.... °C

Precautions T B

1. Thermometer should not touch the wall of the beaker. Temperature (in °C) C
2. The molten wax should be well stirred till it starts freezing.

3. The test tube should be suffi ciently dipped in the water.
D
Sources of Error Time (in minutes) X

1. Thermometer may be inaccurate. Fig. 1.2: Cooling curve of molten wax
2. Impurities in the wax change its freezing or melting point.

ACTIVITY - 2

Aim
To observe and explain the eff ect of heating on a bi-metallic strip.

Apparatus and Materials Required

A bi-metallic strip of iron and brass or two thin identical strips of iron and brass each about 1 cm × 20 cm,
working facility for riveting the strips, heating arrangement, and clamp stand

Making the bi-metallic strip: For this we need identical metal strips of iron and brass of the size
about 1 cm × 20 cm. Cover one of the strips with the other one and fi x rivets on them at the length intervals

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