Cleaning Capacity of Soap in Soft & Hard Water: Comparative Study

Cleaning capacity of soap in hard water is reduced a lot when compared to that of soft water. Water can be classified as hard water and soft water based on the presence or absence of salts like Calcium and Magnesium in the water. The presence of Calcium and Magnesium salts in water reduces the solubility of the soap in water thus reducing its cleaning capability and foaming capacity. Hence, hard water isn't suitable for cleaning clothes.The hardness in water can also damage our homes. One might often find a film of residue on dishes or spots on clothes if one is using hard water. However, soft water doesn't contain any dissolved salts like Calcium and Magnesium and is suitable for cleaning purposes owing to its foaming capability.

Key Terms: Hard water, soft water, soap, calcium, magnesium,solution, salts.

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Difference Between Hard and Soft Water

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The differences between hard and soft water are as follows:

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Procedure 1

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Objective of the Experiment:

To test the comparative cleaning capacity of soap in hard and soft water.

Apparatus Used:

1. Two test tubes
2. Test tube Stand
3. Measuring Cylinder
4. Soap Solution

Process:

1. Take two test tubes and label them as ‘A’ and ‘B’.
2. Pour 10 ml of soft water in test tube ‘A’ and 10 ml of hard water in test tube ‘B’.
3. Add a few drops of soap solution in test tube ‘A’ and test tube ‘B’.
4. Shake the two test tubes rigorously for the same amount of time and place them in the test tube stand.
5. Observe the result and record it.

Observation:

Conclusion:

• Test tube A contains soft water which when mixed with soap, results in the formation of lather or foam. 
• Test tube B contains hard water which when mixed with soap does not result in the formation of foam or lather.

Precautions:

1. The amount of soap solution prepared should be sufficient for both soft water and hard water.
2. An equal amount of soap solution should be added to both the test tubes.
3. The test tubes should be shaken with the same force for the same amount of time.

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Procedure 2

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Objective of the Experiment:

To test the emulsification of oil in hard water and soft water when soap is added.

Apparatus Used:

1. Two Test tubes
2. Test Tube Stand
3. Measuring Cylinder
4. Oil
5. Soap Solution

Process:

1. Take two test tubes and label them ‘A’ and ‘B’.
2. Add 10 ml of soft water in test tube ‘A’ and 10 ml of hard water in test tube ‘B’.
3. Add 1 drop of oil in test tube A and test tube B.
4. Add a few drops of soap solution to both test tubes.
5. Now, shake the test tubes rigorously for an equal amount of time.
6. Place the test tubes in the test tube stand and observe the changes.
7. Record the result.

Observation:

Conclusion:

• The solution in test tube A emulsifies when soap solution is added. Hence oil emulsifies in soft water.
• The solution in test tube B does not emulsify when soap solution is added. Hence oil does not emulsify in hard water.

Precautions:

• Soap solution should be sufficient for both hard water and soft water.
• An equal amount of soap solution should be added to the test tubes.
• Both the test tubes should be shaken with the same force for the same amount of time.
• The same oil should be used in both the test tubes.

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Things to Remember

• Soap is a cleaning agent that is used for washing clothes, utensils, and for bathing purposes.
• Soft water has no salts and forms foam easily.
• Hard water has salts like Calcium and Magnesium and does not form foam.
• When soap solution is added to both soft water and hard water and mixed well, lather is formed for soft water and it is not formed for hard water.
• When soap solution is added to both soft water and hard water along with oil, it is observed that oil emulsifies with soft water and does not emulsify with hard water.

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