Metals
Properties of metals
Physical properties
- They are malleable which means they can be hammered into any shape without breaking
- They are ductile which means they can be drawn out into wires
- They are sonorous which means they make a ringing noise when you strike them
- They shine when polished
- They are good conductors of electricity and heat
- They have high melting and boiling points. (They are all solid at room temperature, except mercury.)
Chemical properties
- They react with oxygen to form oxides which are basic. For example, magnesium burns in air to form magnesium oxide.
- They form positive ions when they react. For example, magnesium
forms magnesium ions (Mg2+) when it reacts with oxygen.
No mattern how simillar the properties of metals appear to be, they also differ in other ways. E.g.
- Sodium is soft and reacts violently with both air and water.
- Iron also reacts with air and water but much more slowly, forming rust.
- Gold remains totally unchanged after many hundreds of years.
Sodium is therefore said to be more reactive than iron and, in
turn, iron is said to be more reactive than gold.
Reactions of metals with air
Many metals such as sodium, potassium, calcium and magnesium react directly with oxygen to form oxides. For example, magnesium burns brightly in oxygen to form the white powder magnesium oxide.
Magnesium + oxygen → magnesium oxide
2Mg(s) + O2(g) → 2MgO(s)
Magnesium metal
Magnesium oxide
Unoxidised copper wire (left), oxidised copper wire (right)Reactions of metals with water
Reactive metals such as potassium, sodium and calcium react with cold water to produce the metal hydroxide and hydrogen gas. For example, the reaction of sodium with water produces sodium hydroxide and hydrogen.
Sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
The less reactive metals such as magnesium, zinc and iron react slowly with water at room temperature. They will, however, react more rapidly with steam. In their reaction with steam, the metal oxide and hydrogen are formed. For example, zinc produces zinc oxide and hydrogen gas.
Zinc + steam → zinc oxide + hydrogen
Zn(s) + H2O(g) → ZnO(s) + H2(g)
Zinc oxide is yellow when hot, white when cold.
Reactions of metals with dilute acids
Most metals react with dilute acids to produce a salt and hydrogen. For example magnesium reacts with dilute hydrochloric acid to produce magnesium chloride and hydrogen gas.
Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Question
A student investigates the rate of reaction of four metals, calcium, iron, magnesium and zinc, with dilute hydrochloric acid. She uses pieces of metal which are all of the same size.
A gas is produced when the metals react. She uses the apparatus shown below.
The student determines the rate of the reaction between each metal and the dilute acid.
- Describe the two measurements that the student records for each reaction.
- ……………………………………………………….
- …………………………………………………………………[2]
- Place calcium, iron, magnesium and zinc, in order of rate of reaction, from highest to lowest.
- Describe the two measurements that the student records for each reaction.
…………….highest
…………….
…………….
…………….lowest [1]
Solution
- Time taken by the reaction
- Volume of the gas produced
- calcium / Ca
magnesium / Mg
zinc / Zn
iron / Fe
| Reactivity series | Reaction with dilute acid | Reaction with air/oxygen | Reaction with water |
|---|---|---|---|
| Potassium (K) | Reacts to produce salt and hydrogen gas | Burn very brightly and vigorously to produce an oxide | Reacts with cold water to produce hydrogen |
| Sodium (Na) | |||
| Calcium (Ca) | |||
| Magnesium (Mg) | Reacts with steam to produce hydrogen gas | ||
| Aluminium (Al) | Burn to form an oxide with less vigour | ||
| Zinc (Zn) | |||
| Iron (Fe) | |||
| Lead (Pb) | React slowly to form the oxide | No reaction with water or steam | |
| Copper (Cu) | No reaction with dilute acids | ||
| Silver (Ag) | Does not react | ||
| Gold (Au) | |||
| Platinum (Pt) |