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AimThe objective of this experiment is to examine and compare the cleaning effectiveness of a soap sample in soft and hard water.
Apparatus Required 2 beakers
Soap sample
Distilled water
Calcium chloride (hard water sample)
Test cloth or swatch
Measuring cylinder
TheorySoap is composed of the potassium or sodium salt of long chain carboxylic acid, which has a hydrophobic hydrocarbon end and a hydrophilic anionic end. In the presence of water, soap molecules arrange themselves in a way that the hydrophilic end is directed towards the water while the hydrophobic end is directed towards oil, forming an emulsion. Soft water is free from dissolved salts, while hard water contains dissolved salts such as calcium or magnesium. When soap is used in soft water, it generates foam that helps remove dirt particles from clothes, making it suitable for washing. On the other hand, soap used in hard water does not produce foam, making it unsuitable for washing.
ProsedureTake two beakers and label them as ‘soft water’ and ‘hard water.’
Pour 100 mL of distilled water in the ‘soft water’ beaker and 100 mL of water containing 1% calcium chloride in the ‘hard water’ beaker.
Cut a small piece of test cloth or swatch and stain it with any organic matter, such as oil or dirt.
Wash the stained test cloth with the soap sample in the ‘soft water’ beaker.
Repeat the washing process with the same soap sample in the ‘hard water’ beaker.
Rinse the test cloth thoroughly with distilled water and allow it to air dry.
Observe and compare the cleaning capacity of the soap in soft and hard water by examining the test cloth.
Observation and ResultObservations:
The soap lathers more easily in soft water, producing more foam and bubbles.
In hard water, the soap does not lather well and forms a scum or precipitate.
The test cloth washed in soft water appears to be cleaner, with less visible stains than the test cloth washed in hard water.
Result: The cleaning capacity of the soap is higher in soft water as compared to hard water. This is because hard water contains a high concentration of calcium and magnesium ions, which reacts with soap to form scum, making it less effective in cleaning. Therefore, it is recommended to use soft water for washing clothes and personal hygiene to obtain better cleaning results.