Explore Water Topics

The Composition of Water

Water is an amazing substance made from two different elements: Hydrogen (H) and Oxygen (O).

  • The chemical formula for water is H₂O. This means each tiny particle (molecule) of water has:
    • Two Hydrogen atoms
    • One Oxygen atom
  • These atoms are chemically bonded together to form a water molecule.
Evidence: Electrolysis of Water

Scientists can prove water's composition using an experiment called electrolysis. This is like carefully "splitting" water back into Hydrogen and Oxygen using electricity.

In electrolysis (2H₂O → 2H₂ + O₂):

  • Water (H₂O) is broken down.
  • Hydrogen gas (H₂) is produced at one electrode (the negative one, cathode).
  • Oxygen gas (O₂) is produced at the other electrode (the positive one, anode).
  • Importantly, twice as much Hydrogen gas is collected compared to Oxygen gas (by volume). This 2:1 ratio matches the H₂O formula!

This experiment also demonstrates the Law of Conservation of Mass: the total mass of hydrogen and oxygen gases produced equals the mass of water decomposed.

Visualizing Water's Makeup

H₂O Molecule
OHH

A single water molecule: one oxygen atom bonded to two hydrogen atoms.

Electrolysis (2H₂O → 2H₂ + O₂)
-ve+veH₂ GasO₂ Gas

Electricity splits water. More H₂ bubbles form than O₂ bubbles (2:1 ratio).

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