When fat comes in contact with sodium hydroxide, it produces soap and glycerin. Determine whether this is a physical change or a chemical change. Explain your answer.

Answer 1

The reaction between fat and sodium hydroxide, which produces soap and glycerin, is a chemical change. This can be determined by several factors:

1. New Substances Formation: In a chemical change, the original substances undergo a transformation that results in the formation of new substances with different properties. When fat (which is primarily composed of triglycerides) reacts with sodium hydroxide (a strong base), it undergoes saponification, leading to the formation of soap (which consists of fatty acid salts) and glycerin (a polyol). Both of these products possess different chemical compositions and physical properties compared to the original fat and sodium hydroxide.

2. Energy Change: Chemical reactions often involve energy changes, such as heat absorbed or released. The process of saponification can be exothermic, releasing heat as the reaction occurs.

3. Irreversibility: While some physical changes (such as state changes) can be reversible, chemical changes are often more difficult to reverse. The formation of soap and glycerin from fat and sodium hydroxide typically cannot be easily reverted back to the original reactants.

Given these factors, the interaction between fat and sodium hydroxide is clearly a chemical change due to the formation of new products and changes in the structure and properties of the original substances.