LAB ACTIVITY CLASS 9

 Law of conservation of mass

Aim: To find out the change in the mass before and after a chemical reaction.

Material required: Lead nitrate, potassium iodide, distilled water, conical flask, spring balance, small test tube, retort stand, rubber cork, thread etc.,

Procedure:

1. Prepare a solution of lead nitrate by dissolving approximately 2 grams of lead nitrate in 100 ml of water in a 250 ml. conical flask.

2. Prepare a potassium iodide solution by dissolving approximately 2 gm of potassium iodide in 100 water in another conical flask.

3. Take 4 ml solution of potassium iodide in a small test tube from the above prepared solutions.

4. Hand the test tube containing 4 ml of potassium iodide solution in the conical flask containing lead nitrate solution carefully, without mixing the solutions close the flask with a cork.

5. Weight the flask with its contents carefully using spring balance.

6. Now tilt and swirl the flask, so that the two solutions mix.

7. Weight the flask again using the same spring balance.

8. Record the observations.

Observations:

1. Weight of flask and contents before mixing =

2. Weight of flask and contents after mixing = 

3. We observe yellow colour precipitate in the conical flask.

4. I think that a chemical reaction has taken place in the flask.

5. The weights of the flask and its contents doesn’t change during the activity.

6. I conclude that the weight of flask and contents before mixing is equal to after mixing.

Result: A chemical reaction takes place and the mass remains same before and after the chemical reaction. Therefore, mass is neither created nor destroyed in the chemical reaction.