IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

# Density of Water at Different Temperatures

## Introduction

This is a simple experiment which can be given to students of middle school level to get a feel of variation of density of water with temperature. The experiment simply consists of measuring the mass and volume of the liquid and calculating the density.

## Apparatus

A beaker with a mark to fix a volume of 40 ml, hot and cold water, an electronic balance, syringe.

## Procedure

1. Look at the electronic balance and get familiar with it.
2. Put the beaker on the balance and TARE it.
3. Remove the beaker from the balance. Panel reading will become negative. Fill cold water in it up to the mark at the volume 40 ml. You can take help of the syringe to put or remove small amounts of water. Do it carefully, look at the mark only after bringing it at the same horizontal level as the eye. Make sure that the whole water surface is horizontal. One way is to ask help from your partner and look at the mark from opposite sides.
4. Put the beaker back on the balance. Note the reading. This is the mass of the water.
5. Calculate the density of water.
6. Measure the temperature of the water in the beaker. Write the density and temperature in the table.
7. Do the same for warm water.
8. Calculate the average fractional change $$\Delta\rho/\rho$$ in density per degree change in temperature for water.

## Discussion

Why does density decrease with increasing temperature? This is due to the asymmetry in the molecular potential as a function as a function of separation between.

## Note

figure and table to be made