To prepare a true solution of common salt, sugar and alum- Class 9th Science Lab Work

To prepare a true solution of common salt, sugar and alum and distinguish between these on the basis of:
(i) transparency
(ii) filtration criterion
(iii) stability

A true solution is a homogeneous mixture of two or more substances which cannot be separated by the method of filtration. The component that is present in a larger amount is called the solvent. The component present in a smaller quantity is called the solute. A true solution is transparent and stable.

Materials Required
Beakers, Common salt (Sodium chloride), Sugar, Alum, Test tubes, Glass Rod, Water

Step 1: Three beakers are taken and 100 ml of water is added in each of them and labelled them as A, B and C respectively.
Step 2: 10g of finely powdered common salt, sugar and alum is added in each beaker separately.
Step 3: Solution is stirred with the help of glass rod.
Step: Put the solutions in test tubes and labelled them as A, B and C.
Observation Table
Property Experimental Procedure Observation Inference
Transparency Small strip of cellophane paper is pasted on each test tubes and the coloured paper of each test tube is observed from other side of test tube. Colour spot is clearly seen on test tubes as seen from other side. A true solution is transparent.
Filtrate Contents of test tubes labelled as A, B and C are filtrated. No residue is observed on filter paper and clear filtrate is obtained. Solid particles cannot be separated from true solution by filtration.
Stability Leave the test tubes without disturbance for 20-25 minutes. No change in the solutions are observed. The true solutions are stable and do not show deposition of components.

Results and Discussion
True solutions are transparent. They pass through filter paper leaving no residue on the filter paper. The filtrate is also transparent.

(i) Handle the materials and solutions with care.
(ii) While filtering a solution drop the contents along a glass rod into the funnel.
(iii) Keep the sample undisturbed while checking stability.

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