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Conservation of matter

HOW DOES IT WORK?

During any chemical reaction no particles are created or destroyed: the atoms are simply rearranged from the reactants to the end products. The products may have different properties to the reactants however mass is never lost or gained in chemical reactions. Mass is always conserved. This implies that the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.

The French chemist, Antoine Lavoisier (1743 – 1794) was the first person to discover that when a chemical reaction takes place in a closed container, the mass of the products after the reaction is completed is exactly the same as the mass of the reactants.

Lavoisier who is also seen as the father of modern chemistry named the discovery the law of conservation of mass.

Time Allocation: 45 Min
Experiment 1:

Observe the conservation of mass in the reaction between Cal-C-Vita and water.

Experiment 2:

Observe the conservation of mass in the reaction between potassium iodide solution and lead (II) nitrate solution.

Experiment 3:

Observe the conservation of mass in the reaction between a hydrochloric acid solution and a sodium hydroxide solution.

Experiment 1:

Observe the conservation of mass in the reaction between Cal-C-Vita and water.

Time Allocation: 45 Min

AIM: 

To observe the law of conservation of mass in the reaction between Cal-C-Vita and water.

APPARATUS:

  • Cal-C-Vita tablet
  • Water
  • Clear plastic bags (2)
  • Elastic band
  • 250 ml measuring cylinder
  • Electronic balance

METHOD:

  1. Fold one of the plastic bags in such a way that it can fit in the second one and stay upright.
  2. Place the tablet in the first bag.
  3. Use the measuring cylinder to measure 200 ml of water and fill the second bag with the water.
  4. Put the first bag in the bag with water, but do not allow the tablet to come in contact with the water.
  5. After pushing the air out of the bags, the outer bag must be sealed with the elastic band.
  6. Measure the combined mass of the bags and their content.
  7. Turn the bags in such a way that the tablet comes in contact with the water.
  8. Write down all the observations that can be made.
  9. Measure the combined mass of the bags again of the reaction has reached completion.

OBSERVATIONS:

Draw a table to record your observations before and after the reaction

Experiment 2:

Observe the conservation of mass in the reaction between potassium iodide solution and lead (II) nitrate solution.     

    Time Allocation: 45 Min

AIM: 

To observe the law of conservation of mass in the reaction between potassium iodide solution and lead (II) nitrate solution.

APPARATUS:

  • Electronic balance
  • 5L Distilled water
  • 2 x 1000 ml volumetric flasks
  • Spatula
  • 250 ml Erlenmeyer flask with rubber stopper
  • Small test tube
  • Potassium Iodide (KI(s))
  • Lead (II) nitrate (Pb(NO3)2(s))
  • Distilled water

METHOD:

  1. Weigh 3, 3 g of potassium iodide and lead (II) nitrate and transfer into two different 1000 ml volumetric flasks.
  2. Dissolve the solids in distilled water and fill to the 1000 ml mark.
  3. Use the measuring cylinder to measure 15 ml of KI (aq) and transfer into Erlenmeyer flask.
  4. Use another measuring cylinder and transfer 5 ml Pb(NO3)2(aq) to the small test tube.
  5. Place the test tube in the conical flask and close tightly with the rubber stopper.
  6. Measure the mass of the flask and its contents.
  7. Turn the flask upside down and allow the content of the test tube and flask to react.
  8. Note all the observations.
  9. Measure the mass of the flask again.

OBSERVATIONS:

Draw a table to record your observations before and after the reactions.

EXPERIMENT 3:

Observe the conservation of mass in the reaction between a hydrochloric acid solution and a sodium hydroxide solution.

AIM: 

To observe the law of conservation of mass in the reaction between a hydrochloric acid solution and a sodium hydroxide solution.

APPARATUS:

  • 2 X 50 ml beakers
  • 0,1 mol∙dm-3 Sodium Hydroxide solution (NaOH(aq))
  • 0,1 mol∙dm-3 Hydrochloric acid solution (HC (aq))
  • Solution of Bromothymol blue
  • electronic mass meter

METHOD:

  1. Determine and note the masses of two small 50 ml beakers.
  2. Measure 15 ml of hydrochloric acid solution with measuring cylinder and pour into one beaker.
  3. Determine the mass of the beaker and its contents. Calculate the mass of the solution.
  4. Measure 15 ml of sodium hydroxide solution and pour into the second beaker.
  5. Add a few drops of Bromothymol blue and determine the mass of the beaker and its content. Calculate the mass of the solution.
  6. Add the HC (aq) to the NaOH(aq).
  7. Note all observations.
  8. Determine the mass of the beaker and its content.
  9. Calculate the mass of the product.

OBSERVATIONS:

Draw a table to record your observations and compare it to your calculated one: (show all calculations)