# To find Melting Point of Ice and Boiling Point of Water

## Theory

Melting poin is the temperature at which a solid melts to form a liquid. A pure solid always has a fixed melting point. When a solid is heated, at its melting point the temperature becomes constant and it remains constant till whole of the solid melts.

## Materials Required

Beaker, glass funnel, 1/2°C thermometer, stop watch, crushed ice or ice cubes made from pure water, stand etc.

## Procedure

• Take a glass funnel and fix it in a stand as shown in the figure.
• Place a beaker below the funnel.
• Put some crushed ice or ice cubes in the funnel.
• Take the thermometer and find its least count. Also find the least count of the stop watch.
• Fix the thermometer in such a way that bulb of the thermometer is well inside the crushed ice.
• Start the stop watch and note the reading on the thermometer at the same time.
• Continue to take the readings on the thermometer after every 1 minute till it becomes constant.
• This constant temperature is the melting point of ice.

## Observations and calculations

Least count of thermometer = ………………… °C
Least count of stop watch = ………………… s.

## Result and Discussion

Melting poin of ice = Constant temperature attained
= ………………… °C

## Precautions

• Ice used for finding the melting point should be obtained by freezing pure or distilled water.
• When crushing or handling ice, see to it that it is not contaminated.
• Bulb of the thermometer should be well inside the crushed ice.
• Thermometer should not touch the funnel.
• The temperature reading should be taken by keeping the eye parallel to the mercury level.
• Recording of temperature and time should be done simultaneously.

## Theory

Boiling point is a temperature at which a liqudi boils. A pure liquid has a fixed boiling point. At its boiling point, the temperature of a liquid becomes constant till whole of it is converted into vapours.
When a liquid is heated the temperature at which its vapour pressure becomes equal to the external pressure is called its boiling point.
During the determination of boiling point of water, the bulb of the thermometer is kept in steam, just above the level of water in the flask. In this way accurate determination of boiling point of water is possible even when the water used for the experiment is not pure.

## Materials Required

500 ml round bottomed flask, cork with two holes for the flask, delivery tube bent at right angle, wire gauze, stop watch, Bunsen burner, stand, 1/2°C thermometer and some pieces of pumice stone.

## Procedure

• Take a round bottomed flask and fill it half with water. Add some small pieces of pumice stone to avoid bumping.
• Fix the flask in a stand as shown in the fig.
• Take the thermometer and find its least count (take 1/2°C thermometer). Also find the least count of the stop watch.
• Fix the thermometer and a delivery tube in the neck of the flask with the help of a cork. The bulb of the thermometer should not dip in the water. It should be just above the level of water in the flask.
• Put a wire gauge below the flask and start heating it.
• When the water starts boiling vigourously, start the stop watch and note the reading on the thermometer simultaneously.
• Continue taking the readings on the thermometer till it becomes constant.
• This consatnt temperature is the boiling point of water.

## Observations And Calculations

Least count of thermometer = ………………. °C
Least count of stop watch = ……………….. s.

## Result And Discussion

Boiling point of water = Constant temperature attained
= ……………… °C

## Precautions

• The bulb of the thermometer should not dip water. It should be just above the level of water in the flask.
• Continue taking the thermometer readings till it becomes constant.
• Use only a round bottomed flask.
• Use a wire gauze to heat the flask.
• Recording of temperature and time should be done simultaneously.