What is fire foam?

Answer

**Step-by-Step Text Solution:**

1. **Definition of Fire Foam**: Fire foam is a type of fire extinguishing agent that is created by mixing certain chemicals to produce a foam that can smother flames.

2. **Chemical Composition**: The primary component used to create fire foam is sodium bicarbonate (NaHCO3), commonly known as baking soda. When sodium bicarbonate is combined with alum (potassium aluminum sulfate), a chemical reaction occurs.

3. **Formation of Carbon Dioxide**: The reaction between sodium bicarbonate and alum produces carbon dioxide (CO2) gas. This gas is what forms the foam.

4. **Purpose of Fire Foam**: The foam produced serves two main purposes:
- It cools down the fire, reducing the temperature of the burning material.
- It coats the fuel, creating a barrier that prevents the fuel from coming into contact with oxygen, which is necessary for combustion.

5. **Stabilization of Foam**: To ensure that the foam remains stable and effective, protective colloids such as glue or dextrin are added. These substances help maintain the structure of the foam, preventing it from collapsing too quickly.

6. **Historical Context**: Fire foam was invented in Russia, and it has since been used in various fire extinguishing applications due to its effectiveness.