How do soaps work, chemically speaking? Describe their chemical properties and give an example (including chemical formula) of a particular soap.

Soaps work by a process called saponification, in which an alkali (such as sodium hydroxide, NaOH) reacts with a fatty acid (such as stearic acid, C18H36O2) to form a salt of that acid (such as sodium stearate, C18H35NaO2) and glycerol (a byproduct). The resulting salt is hydrophilic (attracted to water) on one end (the head) and hydrophobic (repelled by water) on the other end (the tail). This allows the soap molecules to form micelles, which are clusters of molecules with the hydrophobic tails towards the center and the hydrophilic heads on the outside. When these micelles encounter dirt or oil on a surface, the hydrophobic tails attach to the dirt or oil, while the hydrophilic heads remain in contact with the water, allowing the dirt or oil to be washed away. An example of a particular soap is sodium stearate, which has the chemical formula C18H35NaO2. This can be made by reacting stearic acid (C18H36O2) with sodium hydroxide (NaOH), as described earlier. Sodium stearate is commonly used in soap bars and as a surfactant in various cleaning products.