Final answer:
Soaps are salts of fatty acids traditionally made by reacting animal fats with a base, and they form insoluble compounds in hard water. Detergents, typically derived from petrochemicals, are more effective in hard water due to their sulfate or sulfonate groups that do not form insoluble minerals.
Step-by-step explanation:
Soaps and detergents both serve as cleansing agents and are considered types of salts, but they have distinct chemical properties and behaviors in water, especially hard water. Soaps are salts of fatty acids, typically made historically by boiling animal fats with a strongly basic solution like potassium carbonate or sodium hydroxide.
This reaction yields glycerol and the salts of fatty acids, known as soaps. An example is the sodium salt of stearic acid, sodium stearate, which has a long nonpolar hydrocarbon chain that is hydrophobic, and an ionic carboxylate group that is hydrophilic, making the molecule amphiphilic.
In contrast, detergents are often synthesized from petrochemicals and have a similar amphiphilic structure but with different ionic groups that make them more effective in hard water. Detergents may contain sulfonate or sulfate groups, as in alkylbenzene sulfonates, which are more soluble in hard water and do not form insoluble compounds with calcium and magnesium ions, as opposed to soap.