3. Prepare crystals of alum.
Answer:
The preparation of alum crystals is described below:
Aim: To prepare alum crystals.
Materials Required: Beaker,water, dilute sulphuric acid, alum powder.
Procedure:
(i) Fill the beaker with a cupful of water and carefully add a few drops of dilute sulphuric acid.
(ii) Heat the water until it boils.
(iii) Add alum powder slowly while continuously stirring the mixture to help the powder dissolve. Continue until no more powder can be dissolved.
(iv) Filter the solution and allow it to cool without any disturbance.
(v) Wait until colourless alum crystals appear at the bottom of the beaker.
(vi) Filter-separate them from the solution to obtain dry crystals.
Observation:
After some time colourless crystals of alum will begin to appear in the solution. The colourless alum crystals, both in the solution and after separation using filter paper, are shown below:
Conclusions:
Formation of crystals of alum from solution is an example of a physical change.
“Prepare crystals of alum.” – Solved.
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Solution to Extended Learning – Activities and Projects Question 1
Solution to Extended Learning – Activities and Projects Question 2
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Solution to Activity 5.1
Solution to Activity 5.2
Solution to Activity 5.3
Solution to Activity 5.4
Solution to Activity 5.5
Solution to Activity 5.6
Solution to Activity 5.7
Solution to Activity 5.8
Solutions to Chapter 5 Physical and Chemical Changes
