A substance reacts rapidly with oxygen, releasing heat and light. Complete combustion produces CO₂ and H₂O. Incomplete combustion can produce carbon monoxide.
An acid (H⁺ donor) reacts with a base (OH⁻ donor) to produce a salt and water. The pH moves toward 7 (neutral). Used in antacids and industrial processes.
Plants convert carbon dioxide and water into glucose (sugar) using sunlight. This is the foundation of almost all food on Earth.
→ Every breath of oxygen you take came from this reaction
🏃 Cellular Respiration
Combustion
C₆H₁₂O₆+6O₂
→
6CO₂+6H₂O+ ATP
The reverse of photosynthesis — cells break down glucose with oxygen to release energy (ATP) for all bodily functions.
→ Happens in every cell of your body right now
🔥 Burning Methane
Combustion
CH₄+2O₂
→
CO₂+2H₂O
Natural gas (methane) burns completely in oxygen, releasing heat and light. Used in cookers, boilers, and power stations worldwide.
→ One of the cleanest-burning fossil fuels
🌊 Electrolysis of Water
Decomposition
2H₂O+ energy
→
2H₂+O₂
Passing electricity through water splits it into hydrogen and oxygen gas. Used to produce green hydrogen fuel from renewable energy.
→ The future of clean energy storage
🦷 Rusting Iron
Synthesis / Redox
4Fe+3O₂+water
→
2Fe₂O₃
Iron atoms lose electrons to oxygen in the presence of water. The reddish-brown iron(III) oxide (Fe₂O₃) forms on the surface as rust.
→ Costs the global economy ~$2.5 trillion per year
🧁 Baking Soda + Vinegar
Acid-Base
NaHCO₃+CH₃COOH
→
CO₂↑+H₂O+NaCH₃COO
Baking soda (a base) reacts with acetic acid in vinegar. The CO₂ gas produced causes the fizzing. The same reaction leavens cakes and bread.
→ You can try this safely at home right now
💡 Haber Process
Synthesis
N₂+3H₂
⇌
2NH₃
Nitrogen and hydrogen react under high pressure and temperature with an iron catalyst to make ammonia — the basis of all synthetic fertilisers.
→ Feeds roughly half of all people alive today
🔋 Zinc-Carbon Battery
Redox
Zn
→
Zn²⁺+2e⁻
In a battery, zinc is oxidised (loses electrons) at the anode. The electrons flow through the external circuit as electric current, powering devices.
→ The same principle powers lithium-ion phone batteries
In a balanced chemical equation, the number of atoms of each element must be the same on both sides. Use the + / − buttons to adjust the coefficients (the numbers in front of each compound) until all atoms are balanced.
Adjust coefficients to balance the equation
What is this?
Chemical reactions are processes where atoms rearrange to form new substances. The Chemistry lab lets you explore reaction types, see famous reactions, and practice balancing equations.
Why does it matter?
Every medicine, material, fuel, and food involves chemistry. Understanding reactions helps you understand life, industry, and the physical world from cooking to climate change.
Key terms
Reactants — substances that enter a chemical reaction (left side of equation)Products — new substances formed during a reaction (right side)Coefficient — the number in front of a formula showing how many molecules are involvedBalanced equation — equal number of each type of atom on both sidesConservation of mass — atoms are never created or destroyed in a reactionCatalyst — speeds up a reaction without being consumed (e.g. iron in Haber process)
🎯 Try this challenge
Go to Balance It! and balance the combustion of methane (CH₄ + O₂ → CO₂ + H₂O). Once done, count the total atoms on each side to confirm the law of conservation of mass holds.
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