Expansion of liquid due to heat in Temperature and its Measurements – Class 7 Science Experiment

Chapter Name: Temperature and its Measurements

Activity Name: Expansion of liquid due to heat in Temperature and its Measurements

Activity Description:

Required Items:

1. Flat-bottomed flask
2. Colored water
3. Cork with a capillary tube
4. Metal trough
5. Boiling hot water

Step by Step Procedure:

1. Take a flat-bottomed flask and fill it with colored water.
2. Fix a cork with a capillary tube in the mouth of the flask, ensuring that the level of water in the capillary tube is visible (Fig 9).
3. Place the flask in a metal trough.
4. Carefully pour boiling hot water into the metal trough until the water level in the trough is at least as high as the water level inside the flask.
5. Observe the level of colored water in the capillary tube. Record any changes in the water level due to the expansion of the liquid as it is heated.

Experiment Observations:

• As boiling hot water is poured into the metal trough, the colored water in the capillary tube rises, indicating expansion due to heat.

6. Remove the flask from the metal trough and place it outside or on a cool surface.
7. Observe the colored water level in the capillary tube after the flask has been outside for some time.
8. Record any changes in the water level due to the contraction of the liquid as it cools down.

• After taking the flask out of the trough and keeping it outside, the colored water level in the capillary tube decreases, indicating contraction due to cooling.

Precautions:

1. Handle the boiling hot water with care to avoid any burns or accidents.
2. Use a flat-bottomed flask to ensure stability during the experiment.
3. Make sure the cork with the capillary tube is securely fixed to prevent any leaks.
4. The metal trough should be of an appropriate size to hold the flask securely and to contain enough hot water for observation.
5. Avoid any sudden movements or disturbances during the experiment to obtain accurate observations.

Lesson Learnt from Experiment:

The experiment demonstrates that liquids like water and mercury expand when heated and contract when cooled. This principle is used in thermometers to indicate temperature changes. The expansion and contraction of liquids are utilized to measure and quantify temperature variations accurately.