With air, water and acid
Sodium moves fast across cold water. Copper stays in it and does nothing.
- Sodium, iron and copper stand in the same water.
- Sodium moves fast. Iron needs steam. Copper stays still.
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The rule
The reactivity series is a list of metals, most reactive first. For example: sodium, magnesium, zinc, iron, copper. Hydrogen is also placed in it, between iron and copper. Above hydrogen means higher than hydrogen in that list. Dilute means mixed with a lot of water.
Metals react with oxygen to give metal oxides. Some metals react with water, and some only with steam. Metals above hydrogen react with dilute acid. They give a salt and hydrogen.
Sodium and potassium react very fast. Real labs keep them under kerosene. Kerosene is an oil. It keeps air and water away. Only a teacher may show them.
| Metal and reagent | Equation |
|---|---|
| Magnesium burns in air | 2Mg + O₂ → 2MgO |
| Sodium and cold water | 2Na + 2H₂O → 2NaOH + H₂ |
| Magnesium and dilute acid | Mg + 2HCl → MgCl₂ + H₂ |
Worked example
Sodium, magnesium, zinc, iron and copper are each tried with dilute acid. Sodium is far too fast to try. Of the rest, magnesium fizzes fastest, then zinc, then iron. To fizz is to give off bubbles of hydrogen. Copper gives no bubbles, because it is below hydrogen.
Hydrogen burns with a pop sound. With nitric acid, hydrogen is not usually released. Magnesium and manganese release it with very dilute nitric acid.
Watch out!
Copper does not fizz with dilute acid. It still reacts with oxygen when heated.