Give an example of a metal which
(a) Is a liquid at room temperature.
Answer: Metals are genrally available as solid at room temperature. But mercury is an exception. Mercury is available as liquid at room temperature.
(b) Can be easily cut with a knife.
Answer: We know that metals are hard. But sodium and gallium are metals which are soft enough to be cut by knife.
(c) Is the best conductor of heat.
Answer: Silver is the best conductor of heat and electricity.
(d) Is a poor conductor of heat.
Answer: All metals are good conductor of heat and electricity. But lead is a poor conductor of heat.
Explain the meanings of malleable and ductile.
Answer: Malleable: Metals can be beaten into thin sheets and hence they are called malleable.
Ductile: Metals can be drawn into thin wires and hence they are called ductile.
A malleable metal is also ductile and these properties are present in almost all the metals. Metals can be given desired shape just by applying physical factor, i.e. force. This makes them ideal and user-friendly for making various useful items, right from a needle to a huge ship.
Why is sodium kept immersed in kerosene oil?
Answer: Sodium is a highly reactive metal and it reacts vigorously with water even at room temperature. Sodium is so reactive that it can even react with the atmospheric moisture. This reaction is highly exothermic which produces fire as well. Sodium is kept immersed in kerosene oil to prevent its reaction with water and to prevent accidental fire.
Write equations for the reactions of
(a) iron with steam
Answer: 3Fe + 4H2O ⇨ Fe3O4 + 4H2
(b) calcium and potassium with water
Answer: Ca + 2H2O ⇨ Ca(OH)2 + H2
2K + 2H2O ⇨ 2K(OH)2 + H2
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
| Metal | Iron(II) sulphate | Copper(II) sulphate | Zinc sulphate | Silver nitrate |
|---|---|---|---|---|
| A | No reaction | displacement | ||
| B | Displacement | No reaction | ||
| C | No reaction | No reaction | No reaction | Displacement |
| D | No reaction | No reaction | No reaction | No reaction |
Use the Table above to answer the following questions about metals A, B, C and D.
(a) Which is the most reactive metal?
Answer: B is the most reactive metal
(b) What would you observe if B is added to a solution of Copper(II) sulphate?
Answer: When B is added to copper (II) sulphate solution, it displaces copper.
(c) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer: B > A > C > D
Explanation: Metal A is less reactive than iron but more reactive than copper because it is displacing copper from copper sulphate. If you will refer to reactivity series, you will find that this metal shall be less reactive than zinc and more reactive than silver. So, no reaction takes place with zinc sulphate solution and displacement reaction takes place with silver nitrate solution.
Metal B displaces iron so it will also displace copper and silver from respective solutions. This means that metal B causes displacement reaction in three cases. So it is the most reactive one, followed by A, C and D in that order.
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