Metals & Non-metals - Class 10th Science
NCERT In Text Solution
Question: 1. Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
Answer:
(i) Mercury
Explanation: Mercury is only metal which is liquid at room temperature
(ii) Sodium
Explanation: Metals are generally hard, but some metals are so soft that can be cut using a knife. Sodium is an example of such metal.
(iii) Silver
Explanation:
All metals are conductor of heat and electricity. Among which copper, gold, silver, and aluminium are very good conductor of heat and electricity.
But, Silver is the best conductor of heat and electricity.
This is the cause that electric wires are made of copper and aluminium. Electric wires are made of copper and aluminium and not of silver, because silver is very costly metal.
(iv) Lead
Explanation: Lead is the poor conductor of heat.
Question: 2. Explain the meanings of malleable and ductile.
Answer:
Malleable : Substances which can be beaten or hammered into thin sheets are called malleable. Metals are malleable because metals can be hammered into thin sheets.
Ductile : Ductility is a property of metals which enable them to drawn into thin wires. So, metals are called ductile.
This is the cause that aluminium and copper are used for making electric wires. Although conductivity is also necessary for making of electric wires, metals are good conductor of heat and electricity.
Question: 3. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is very much reactive metal. Sodium reacts vigorously with water. Sodium is so reactive that it reacts with moisture present in air. Thus, to prevent sodium getting reacted with moisture present in air, sodium is kept immersed in kerosene oil.
Question: 4. Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water
Answer:
(i) Equation for reaction of Iron with steam
(ii) Equation for reaction of calcium with water
Calcium metal reacts with water vigorously and produces calcium hydroxide and hydrogen gas.
Equation for reaction of potassium with water
Potassium metal reacts vigorously with water and produces potassium hydroxide and hydrogen.
Reaction of potassium and water is highly exothermic. In this reaction also evolved hydrogen gas catches fire immediately.
Question: 5. 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.
(i) Which is the most reactive metal?
(ii) What would you observe if B is added to a solution of Copper(II) sulphate?
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer:
(i) B is the most reactive metal
(ii) If B is added to the solution of Copper (II) sulphate, B displaces copper.
(iii) B > A > C > D
Question: 6. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Answer: Hydrogen gas is produced, when dilute hydrochloric acid is added to a reactive metal.
Example:
When zinc is added to hydrochloric acid hydrogen gas is formed along with zinc sulphate.
Chemical reaction for reaction of iron with dilute sulphuric acid
When iron reacts with dilute sulphuric acid, hydrogen gas is formed.
Question: 7. What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Answer: When zinc is added to the solution of iron (II) sulphate, zinc displaces iron and forms zinc sulphate. This happens because zinc is more reactive than iron. This is an example of displacement reaction.
