Chemical Reactions & Equations

Chemical reactions have four key features that make them different from simple physical changes. Compounds get broken apart or new ones form, at least one completely new substance appears, there's always a measurable energy change (like heat or light), and crucially - no atoms are ever created or destroyed in the process.

Chemical equations are like recipes that show exactly what's happening during a reaction. The reactants (starting materials) go on the left side, whilst the products (what you end up with) appear on the right side after an arrow.

You can write equations in two ways. Word equations use everyday language - for example: Sodium + oxygen → Sodium Oxide. Symbol equations use chemical symbols and must be balanced, meaning you need the same number of each type of atom on both sides.

💡 Remember: Balancing equations is like making sure you have the same number of Lego bricks before and after building - atoms can't just disappear or appear from nowhere!

The balanced symbol equation 4Na + O₂ → 2Na₂O shows that four sodium atoms plus one oxygen molecule create two sodium oxide compounds. This follows the golden rule that atoms are simply rearranged, never lost or gained.