CLASS.X-Experiment No.9-To study the cleaning action of soap in hard and normal water

Experiment No.9

To study the cleaning action of soap in hard and normal water

Aim:

The aim of this experiment – Studying the comparative cleaning capacity of a sample of soap in soft and hard water.

Materials required:

1. Test tube (2)
2. Measuring cylinder
3. Test tube stand

Theory:

Soap is the potassium or sodium salt of long chain carboxylic acid. The basic structure consists of a long hydrophobic hydrocarbon end and a hydrophilic anionic end. The hydrophobic end is the tail whereas the hydrophilic end is the head. Emulsion in water is formed when the ionic end of soap molecule is towards water and the non ionic end of soap molecule is towards oil.

What is soft water?

The water which has no salt in it is called soft water. When soap is used in soft water it generates foam which is a cleansing property and removes dirt particles from clothes. Therefore, this water is suitable for washing.

What is hard water?

The water which has dissolved salts such as calcium or magnesium in it is called hard water. When soap is used in soft water it does not generate foam. Therefore, this water is unsuitable for washing.

Experimental Setup:

Procedure 1:

1. Take a test tube and mark it as X.
2. Add 10 mL of soft water in it.
3. Take another test tube and mark it Y.
4. Add 10 mL of hard water in the test tube Y.
5. Add a few drops of soap solution in both the test tubes.
6. Shake test tube X and Y strongly for equal amount of time.
7. Place both the test tubes in the test tube stand.
8. Observe and record the results.

Observation and results:

Test tube	Observation
X	Forms lather
Y	White precipitate is formed

Results:

• The test tube which is marked X forms foam when mixed with soap solution.
• The test tube which is marked Y does not form foam but forms a white precipitate when mixed with soap solution.

Precautions to be taken during the experiment:

• Make sufficient amount of soap solution so that the same solution is used for soft water as well as hard water.
• Add equal amount of soap solution to both the test tubes.
• Take equal concentration test tubes.
• Mix the soap solution added to the test tubes in a similar pattern and for equal period of time.

Procedure 2:

1. Take a test tube and mark it as P.
2. Add 10 mL of soft water in it.
3. Add one drop of cooking oil.
4. Take a test tube and mark it as Q.
5. Add 10 mL of hard water in it.
6. Add one drop of cooking oil.
7. Add a few drops of soap solution to P and Q.
8. Shake test tube P and Q strongly for equal amount of time.
9. Place both the test tubes in the test tube stand.
10. Observe and record the results.

Observation and results:

Test tube	Observation
P	Oil emulsifies
Q	No emulsification

Results:

• The test tube which is marked P emulsifies due to the presence of soap solution.
• The test tube which is marked Q does not emulsify due to the presence of soap solution.

Precautions to be taken during the experiment:

• Make sufficient amount of soap solution so that the same solution is used for soft water as well as hard water.
• Add equal amount of soap solution to both the test tubes.
• Take equal concentration test tubes.
• Mix the soap solution added to the test tubes in a similar pattern and for equal period of time.
• Use same cooking oil in both the test tubes.

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