How does Liquid Plumber work?
(Q&A by Jamie Mattson)

There are two ways to get a clogged drain cleaned. You could spend an arm and a leg for a plumber to clean the pipes for you. You could also do it yourself at a very affordable price with a product like Liquid Plumber.
A clogged drain is usually the result of solidified grease and hair stuck in the pipe. Simple water won’t rinse away the grease. This is because grease doesn’t dissolve in water. Liquid Plumber dissolves grease in a way water can’t. When Liquid Plumber is poured down your drain, it comes in contact with the clogged area and creates a reaction. This reaction, which is called an exothermic reaction, creates heat. As the grease warms up, it liquefies and starts to move down the drain taking the other debris with it.

Source: Merrill Chemistry by: Smoot, Smith, Price; Glencoe, 1998.