In a chemical reaction, the type of change that occurs is a change in the arrangement and bonding of atoms within molecules. This results in the formation of new substances with different chemical properties compared to the original substances.

Here's a breakdown:

* Rearrangement of Atoms: The atoms within the reactants (starting materials) break their existing bonds and rearrange to form new bonds, creating products (the resulting substances).

* Formation of New Substances: The products have a different chemical composition and structure than the reactants, leading to different physical and chemical properties.

* Energy Changes: Chemical reactions can either release energy (exothermic) or require energy input (endothermic) to occur.

Examples:

* Burning wood: Wood (cellulose) reacts with oxygen to produce carbon dioxide, water, and heat.

* Baking a cake: Flour, sugar, eggs, and other ingredients react to form a cake, a completely new substance with a different texture and flavor.

* Rusting of iron: Iron reacts with oxygen and water to form iron oxide (rust), a different substance with a different color and structure.

Important Note: Chemical changes are irreversible, meaning they cannot be undone easily by simple physical means. You need another chemical reaction to convert the products back into the original reactants.