The substance made when alkalis react with oils is soap.

This reaction is called saponification.

Here's a breakdown:

* Alkali: A strong base, typically sodium hydroxide (NaOH) or potassium hydroxide (KOH).

* Oil: A triglyceride, which is a type of fat containing glycerol and three fatty acids.

* Reaction: The alkali breaks down the triglyceride, releasing glycerol and fatty acids. The alkali then reacts with the fatty acids to form soap molecules.

So, the chemical process of soap making involves the following steps:

1. Hydrolysis: The alkali breaks down the triglyceride molecules in the oil.

2. Salt Formation: The alkali reacts with the fatty acids to form salts, which are the soap molecules.

This is how soap is made traditionally, and even today, some soapmakers still follow this process.