Required practical 8: Water

Question 1

What is the method on how do we establish if a sample of water is pure?

Answer 1

1) First, put a small amount of water onto a piece of universal indicator paper to check the pH if the pH is not 7 then the water is not pure but if it is 7 it sill does not mean the water is pure as the water could still contain dissolved solids and now we need to test for them.
2) Now we use a balance to weigh an empty evaporating basin to record the mass.
3) Now we fill the evaporating basin with our water sample and place this on a tripod and gauze.
4) Now use a Bunsen burned to gently heat the water until it has all evaporated.
5) At this point, we allow the evaporating basin to cool and then weigh it again and if the water sample contained any dissolved solids then the mass of the empty evaporating basin will have increased because the water has evaporated but the dissolved solids will have formed crystals on the surface of the evaporating basin meaning the water was not pure but if the mass didn’t increase the water could be pure.

Question 2

How do we purify water by distillation?

Answer 2

1) Get a conical flask with our water sample inside and put it on a tripod and gauze and attach a delivery tube to the top of the conical flask pointed into a test tube sitting in a beaker containing ice and water.
2) Now gently heat the water using a Bunsen burner.
3) At this point the water will evaporate and form water vapour.
4) The water vapour now travels along the collecting tube.
5) When the water vapour enters the cold test tube it condenses back into liquid water (Distilled water).