Reactions with water
Introduction:
Water reactions help show how easily an element loses or gains electrons.
Highly reactive metals (like sodium, potassium) react vigorously with cold water, producing alkaline solutions (hydroxides) and hydrogen gas, often releasing heat.
Moderately reactive metals (like calcium, magnesium) react more slowly; some need hot water or steam.
Less reactive metals (like iron, zinc) react only with steam, forming metal oxides + hydrogen.
Unreactive metals (like gold, silver) do not react with water.
Some non-metals react with water to form acids, but many show little or no reaction.
Structure of water molecule:
• 1 oxygen atom bonded to 2 hydrogen atom makes up a water molecule.
• Polar covalent bonds (oxygen is more electronegative)
• The oxygen atom carries a partial negative charge and hydrogen carries a partial positive charge.
• This polarity makes water able to interact with charged particles and accept electrons.
The process:
Step-by-step process (Grade 10–11 level):
1. Contact between metal and water
When a reactive metal touches water:
Water molecules (H₂O) surround the metal surface
Because water is polar, it can interact with charged particles
2. Metal loses electrons (oxidation)
Metal atoms at the surface release electrons:
M \rightarrow M^+ + e^-
These electrons don’t just float away—they are immediately taken by nearby water molecules
3. Water gains electrons and splits (reduction)
Water molecules use those electrons to break their bonds:
2H_2O + 2e^- \rightarrow H_2 + 2OH^-
Hydrogen atoms join → form H₂ gas (bubbles)
The rest becomes hydroxide ions (OH⁻)
4. Formation of solution
Now you have:
M^+ (metal ions)
OH^- (hydroxide ions)
They stay dissolved:
M^+ + OH^- \rightarrow MOH
→ This makes the solution alkaline (basic)
5. What you would observe
Fizzing → hydrogen gas forming
Heat → energy released
Metal disappears (gets used up)
Solution becomes slippery/basic
6. What drives the whole process
Metals want to lose electrons (low ionization energy)
Water can accept electrons and split
New bonds formed are more stable, so energy is released
Final core idea
At the atomic level, it’s a continuous cycle:
Metal → gives electrons
Water → takes electrons and breaks
Products form → system becomes more stable