Chemical Equations

What Is a Chemical Equation?

Chemical equations are like recipes that show what goes into a chemical reaction and what comes out.

• A chemical reaction is when substances change into something new (like baking a cake).
• A chemical equation shows this change using chemical formulas and symbols.
• Example: H2​+O2​→H2​O  (hydrogen + oxygen = water.)
  • The arrow (→) means “yields” or “produces.” 

• • The small numbers written after chemical symbols are called subscripts.

• • They show how many atoms of each element are in a molecule.

Why Do We Balance Equations?

Balancing chemical equations follows the rule that matter can’t be created or destroyed — just rearranged.

• Every atom on the left (reactants) must appear on the right (products).

• That’s why we balance chemical equations: to show the Law of Conservation of Mass.

• Example: H2​+ ½ ​O2​ → H2​O or 2H2​ + O2​→ 2H2​O
• Coefficients (big numbers in front) are used to balance equations, not subscripts!

Fun Facts

Here are some interesting facts about chemical equations:

• Antoine Lavoisier, the “father of modern chemistry,” helped create the rules for balancing equations.
• Different metal salts in the equations create colors, like strontium for red and copper for blue.
• Your body runs thousands of tiny chemical equations every second to keep you alive.
• Photosynthesis is a chemical equation that plants use to convert sunlight into energy!

          6CO2​ + 6H2​O + light energy → C6​H12​O6 ​+ 6O2​

Review

Let’s quickly recap what we learned about chemical equations:

• What does a chemical equation describe? A Chemical Reaction
• What law must we follow when balancing chemical equations? Law of Conservation of Mass
• What symbol separates reactants from products? An Arrow
• What do we use to balance equations? Coefficients