Page 240 - Chemistry ICSE Class IX

7 Soaps and Detergents

BASIC CONCEPTS

Soap

Sodium or potassium salt of a long chain fatty acid is called a soap. For example, sodium stearate is a soap.
Soaps do not perform well in hard water.
C H COONa C H COONa
35
15
17
31
sodium stearate (soap) sodium palmitate (soap)
Detergent
A surface-active agent which cleans a dirty surface by lowering the surface
tension of water is called detergent. Generally, the term detergent is used for
synthetic detergents only. 5QFKWO n-dodecylbenzene sulphonate is a typical
detergent. Detergents can be used even in hard water. Detergents cause pollution of water in waterbodies,
such as rivers and ponds.

EXPERIMENT 7.1

Objective
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Apparatus Required

Beakers, Test tubes

Material Required
Soap solution (1%), Detergent solution (1%), Sample of hard water

Procedure

Proceed through the following steps:

y Take two test tubes. Label these as A and B.
y Pour about 5 mL of hard water in each test tube.
y Add 1 mL of soap solution to test tube A, and 1 mL of detergent solution to test tube B. Shake the test
tubes vigorously.

y Observe, if lather is formed in the solutions.