4 Types of Chemical Reactions

6th Grade Science

Physical Changes and Chemical Reactions:

Physical Change

Physical changes are about energy and states of matter.

Melting an Ice-Cube

Chemical Reaction

Chemical changes happen on a molecular level when you have two or more molecules that interact and create a new molecule or two.

Physical or Chemical?

Crushing a canMelting an Ice

Cube

Physical or Chemical?

A Rusty NailThe Statue of

Liberty

4 types of Chemical Reactions

1. Synthesis Reaction

A + B AB

Reactants A and B combine chemically to form a more complex molecule, AB. AB then stores energy in its bonds.

4 Types of Chemical Reactions

2. Decomposition Reactions

AB A + B

The molecules AB is chemically broken down to smaller molecules, and in doing so, energy is released.

4 Types of Chemical Reactions

3. Exchange Reactions

AB + CD AD + CB

These reactions involve both synthesis and decomposition reactions. The reactants exchange parts to yield new chemical compounds.

4 Types of Chemical Reactions

4. Reversible Reactions

A + B AB

Chemical bonds can be made and they can be broken depending on the requirements of the body.

Example: Glycogen molecules can be synthesized from glucose molecules for storage in liver cells, and glycogen can be decomposed to glucose by the liver during periods of low blood sugar.