* Atoms: The fundamental building blocks of matter, they remain the same throughout the chemical change. For example, a carbon atom in a piece of wood will still be a carbon atom after the wood burns.
* Bonds: The forces that hold atoms together to form molecules. These bonds are broken and reformed during chemical changes. This rearrangement of bonds leads to the creation of new substances with different properties.
Here's a simple analogy:
Imagine you have a set of building blocks. You can rearrange them to create different structures like a house, a tower, or a car. The building blocks themselves remain the same, but the way they are connected and arranged changes, resulting in different structures.
In a chemical change:
* Reactants: The substances that are present at the beginning of the reaction.
* Products: The new substances that are formed after the chemical reaction.
The atoms from the reactants rearrange their bonds and form new bonds to create the products. This process results in the formation of new substances with different properties.
Examples:
* Burning wood: The wood reacts with oxygen to produce carbon dioxide, water, and ash. The carbon, oxygen, and hydrogen atoms in the wood rearrange their bonds to form new molecules.
* Rusting iron: Iron reacts with oxygen to form iron oxide (rust). The iron and oxygen atoms rearrange their bonds to form a new compound with different properties.
Key point: The key difference between a physical change and a chemical change is that in a physical change, the substance's appearance may change but its chemical composition remains the same. In a chemical change, the chemical composition of the substance changes, leading to the formation of new substances.
