Lesson 7 of 12

⚖ Chemical Reactions

🎯 Grades 6–8 ⏱ ~35 minutes 🟡 Intermediate

What You'll Learn

What happens during a chemical reaction (bonds broken and formed)
How to read and balance a chemical equation
Signs that a chemical reaction has occurred
Exothermic vs endothermic reactions

⚖ Reaction Simulator

Select a reaction type to see a visual simulation and the balanced equation.

⚖ Equation Balancer Checker

Balance the equation by entering coefficients. Check if atom counts match on both sides.

What Is a Chemical Reaction?

In a chemical reaction, atoms rearrange — old bonds break and new bonds form — creating new substances (products) from starting substances (reactants). Atoms are never created or destroyed, just rearranged.

Signs of a reaction: color change, gas produced (bubbles), temperature change, precipitate (solid) forms, light emitted.

Balanced Equations

The Law of Conservation of Mass: atoms in = atoms out. Balanced equation for water formation: 2H₂ + O₂ → 2H₂O. Coefficients (big numbers) multiply all atoms in that molecule.

Exothermic — releases energy (heat/light). Combustion, explosions. Endothermic — absorbs energy. Photosynthesis, cold packs.

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Fire Is a Chemical Reaction

Fire is the rapid oxidation of fuel — a combustion reaction. The bright glow comes from hot carbon particles. A candle flame burns at ~1,000°C. Without oxygen (like in space), fire cannot burn — which is why you can blow out a candle!

❓ Check Your Understanding

← Atoms & Periodic Table Forces & Newton's Laws →