Question

What could be the observation for cleaning of soap in hard and soft water class 10 science practical manual

Answer 1

Water is used for washing along with the soap. The effectiveness and cleansing action of soap depends on the type of water.

> Soft water: The type of water which produces lather with the soap is called soft water. Washing of clothes is very effective and easy in soft water.

> Hard water: The type of water which does not produce lather with the soap is called hard water. It contains dissolved salts in it. The soap forms scum with hard water and not fit for laundry purpose.

Answer 2

Answer:

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$\large\bf\pink{AIM}$

To study the comparative cleaning capacity of a sample of soap in soft and hard water.

$\large\bf\red{MATERIALS \:REQUIRED}$

Tap water, distilled water,

calcium hydrogen carbonate (0.5 g),

calcium chloride (0.5 g),

calcium sulphate (0.5 g),

soap sample (1 g),

spatula,

physical balance,

weight box,

five test tubes,

three beakers (100 ml),

four glass rods,

measuring cylinder,

a measuring scale and three droppers

$\large\bf\blue{THEORY}$

Water that does not contain a significant amount of dissolved minerals such as compounds of calcium and magnesium is soft water. It produces lather with a little amount of soap. Hard water is water that has high mineral content, it has high concentrations of Ca2+ and Mg2+ ions. Calcium and magnesium hydrogen carbonates, chlorides and sulphates in water render it hard. When soap is added to hard water, it does not form lather. The calcium and magnesium salts in hard water react with soap and form scum, which is insoluble and floats on top of water. Due to the formation of scum, which is calcium or magnesium salt of soap (soap is sodium or potassium salt of fatty acids), soap becomes ineffective in solution and no cleansing occurs. The equations involved in the formation of scum are as follows:

See in above attachment

$\large\bf\blue{PROCEDURE}$

1. Take three beakers (100 ml) and label them as ‘A’, ‘B’ and ‘C

2. Prepare 30 ml soap solution by adding 1 g soap to water in beaker ‘C’.

3. Pour 20 ml tap water in beaker ‘A’ and 50 ml distilled water in beaker ‘B’.

4. Place five test tubes, labelled A, B, C, D and E, in a test tube stand.

5. Using a dropper pour 5 ml of tap water in test tube A, and 5 ml distilled water in the other test tubes labelled as B, C, D and E.

6. To test tube C, D and E add a pinch of calcium hydrogencarbonate, calcium chloride and calcium sulphate respectively using a spatula.

7. Mix the solution well using a glass rod.

8. Using a dropper, add 3 ml of soap solution to the test tube A. Measure the length of the solution present in the test tube A and record this in table.

9. Shake test tube A, ten times by placing thumb on its mouth.

10. Observe whether foam is formed by shaking the test tube and record your observations.

11. Measure the length of content (foam and solution) present in the test tube immediately with the help of a measuring scale.

12. Repeat steps 8 to 11 with the remaining water samples (B, C, D and E) and record your observations.

$\large\bf\blue{OBSERVATION}$

Volume of water samples taken in test tube = 5 ml.

Volume of soap solution added to each test tube = 3 ml.

cbse-class-10-science-practical-skills-cleaning-capacity-of-soap-in-hard-and-soft-water-6

$\large\bf\blue{RESULTS}$

Maximum length of foam is produced in water sample(s) …………………………………

Scum is formed in water sample(s) ……………………………

The water sample most suitable for washing purpose is …………………………..

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