Change in mass in Atoms And Molecules – Class 9 Science Experiment

Chapter Name: Atoms And Molecules

Activity Name: Change in mass in Atoms And Molecules

Activity Description:

Required Items:

• Lead nitrate
• Potassium iodide
• Distilled water
• Conical flask (250ml)
• Test tube
• Spring balance
• Stand
• Rubber cork
• Thread

Step by Step Procedure:

1. Dissolve approximately 2 grams of lead nitrate in 100 ml of distilled water to prepare a lead nitrate solution.
2. Dissolve approximately 2 grams of potassium iodide in 100 ml of water to prepare a potassium iodide solution.
3. Take 100ml of the lead nitrate solution in a 250ml conical flask.
4. Take 4ml of the potassium iodide solution in a test tube.
5. Hang the test tube carefully in the flask without mixing the solutions. Cover the flask with a rubber cork. (Refer to figure 1 for setup)
6. Carefully weigh the flask with its contents using a spring balance.
7. Tilt and swirl the flask to mix the two solutions (Refer to figure 2).
8. Weigh the flask again using the same spring balance as shown in figure 3.
9. Record your observations:
   • Weight of flask and contents before mixing =
   • Weight of flask and contents after mixing =

Experiment Observations:

• The initial weight of the flask and its contents before mixing the solutions.
• The final weight of the flask and its contents after the chemical reaction occurs.

Precautions:

• Handle lead nitrate and potassium iodide with care, as they may be hazardous if mishandled.
• Ensure that the test tube is securely hung in the flask and properly covered with the rubber cork.
• Use a clean and dry spring balance for accurate weight measurements.
• Follow proper laboratory safety guidelines while conducting the experiment.

Lesson Learnt from Experiment:

The experiment helps in understanding the concept of conservation of mass during a chemical reaction. The total mass of the substances before the reaction is equal to the total mass after the reaction.