Metals vs Water
Watch sodium and zinc react with water.
What this lesson covers
Why it matters
Sodium reacts violently with cold water — skidding, hissing and sometimes catching fire — while zinc needs steam before it reacts at all.
The idea in plain words
Balance the swap: 2Na + 2H₂O → 2NaOH + H₂. Notice sodium takes the place of hydrogen.
Predict first
Why does sodium react violently with cold water, but zinc needs steam?
Reactivity series ranks metals by their eagerness to lose electrons. Sodium is far more reactive than zinc, so it attacks cold water instantly.
- Sodium is softer than zinc
- Sodium is higher in the reactivity series than zinc — correct
- Zinc is too heavy to react
- Water is not hot enough for sodium
What you do
First, drop sodium into cold water. Then, pass steam over heated zinc. Compare the violence and the products.
Check yourself
What gas is produced in both reactions?
Both equations show H₂ as the gaseous product. Metals displace hydrogen from water.
How do you test for the gas produced by sodium?
Hydrogen is flammable. The observation data notes it is 'vigorous, may catch fire'.
What is the solid product when zinc reacts with steam?
The equation is Zn + H₂O → ZnO + H₂. Zinc oxide is the solid residue.
What is the color of the zinc oxide product?
ZnO is a thermochromic pigment: yellow when hot, white when cold.
- Oxygen
- Hydrogen — correct
- Nitrogen
- Carbon dioxide
- It turns lime water milky
- It relights a glowing splinter
- It catches fire or pops with a burning splinter — correct
- It has no effect on a splinter
- Zinc hydroxide
- Zinc oxide (ZnO) — correct
- Zinc sulphate
- Zinc chloride
- Yellow when hot, white when cold — correct
- White when hot, yellow when cold
- Always black
- Always blue