Question

in an experiment to determine the boiling point of water , mention 2 important precautions to be taken.

Answer 1

Take about 25ml of distilled water in a boiling tube and add 2-3 small pieces of pumice stone.

Close the mouth of the boiling tube with a rubber cork that has two bores and clamp it with the stand.

Introduce a thermometer (temperature range -10 to 110°C) in one bore of the cork of the boiling tube. Keep the bulb of the thermometer  about 3-5 cm above the surface of the water.

Then introduce one end of a delivery tube in the second bore of the cork.

Place a 250ml beaker below the second end of the delivery tube to collect the condensed water.

Heat the boiling tube gently, preferably by rotating the flame.

Note the temperature (t1) when the water starts boiling.

Continue to heat the water till the temperature becomes constant, and the water remains boiling. Note the constant temperature (t2).

Record your observations in tabular form

Precautions:

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

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

Heating of water should be done by rotating the flame.

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

Answer 2

1. Few pieces of pumice stone should be added to the water to prevent bumping on boiling
2. In case of highly flammable liquids,the heating should not be done on direct flame.