CBSE Class 10 Answered

Importance and difference between soaps and detergents is as follows:

• Soap is a triacylglyceride derviative (fat) while detergents are often produced synthetically.
• The head-group of soap a molecule is usually a carboxylate anion while common detergents often use phosphate or sulfate head-groups (ie Sodium dodecyl sulfate).
• Soap's effectiveness is greatly affected by the presence of certain minerals in solution such as those typically associated with hard water. Detergents are usually not affected by minerals in solution. 
• Soaps are the sodium salts of long chain carboxylic acids
• Detergents are sodium salts of long chain benzene sulphonic acids
• Soaps are biodegradable while some of the detergents are non-biodegradable.
• Soaps have relatively weak cleansing action whereas; detergents have a strong cleansing action.
• A detergent is a sodium salt of alkyl benzene sulphonate or of a fatty alcohol sulphate. A soap is a sodium or potassium salt of higher fatty acids.
• A detergent is more effective in hard water. Soaps are less effective in hard water.