NCERT Solutions Class 10 Science Chapter 3 – Metals and Non-metals
NCERT Solutions for Class 10 Science Chapter 3: Metals and Non-metals
This chapter is one of the most important chapters in Class 10 Science, carrying significant weightage in board exams. Understanding the properties of metals and non-metals, their reactions, and extraction processes is crucial for scoring well.
In-text Questions and Answers
Page 40 Questions
Q1. 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 (Hg) is the only metal that is liquid at room temperature
- (ii) Sodium (Na) and Potassium (K) are soft metals that can be easily cut with a knife
- (iii) Silver (Ag) is the best conductor of heat, followed by Copper (Cu)
- (iv) Lead (Pb) and Mercury (Hg) are poor conductors of heat
Q2. Explain the meanings of malleable and ductile.
Answer:
- Malleable: The property of metals by which they can be beaten into thin sheets. Example: Gold and Silver are highly malleable. Aluminum foil is made by beating aluminum.
- Ductile: The property of metals by which they can be drawn into thin wires. Example: Copper and Aluminum are highly ductile and used for making electrical wires.
Page 46 Questions
Q1. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is a highly reactive metal. It reacts vigorously with oxygen and water present in air. The reaction with water is so violent that it can cause fire. To prevent this dangerous reaction and keep sodium safe, it is stored immersed in kerosene oil, which does not react with sodium.
Q2. Write equations for the reactions of (i) iron with steam (ii) calcium and potassium with water.
Answer:
(i) Iron with steam:
3Fe + 4H₂O → Fe₃O₄ + 4H₂
(Iron reacts with steam to form iron(II,III) oxide and hydrogen gas)
(ii) Calcium with water:
Ca + 2H₂O → Ca(OH)₂ + H₂
(Calcium reacts with cold water to form calcium hydroxide and hydrogen gas)
Potassium with water:
2K + 2H₂O → 2KOH + H₂
(Potassium reacts violently with cold water to form potassium hydroxide and hydrogen gas. The reaction is so exothermic that hydrogen gas catches fire.)
Exercise Questions
Q1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal
Answer: (d) AgNO₃ solution and copper metal
Explanation: A more reactive metal displaces a less reactive metal from its salt solution. According to the reactivity series: Cu > Ag, therefore copper can displace silver from silver nitrate solution.
Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
Q2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease (b) Applying paint (c) Applying a coating of zinc (d) All of the above
Answer: (d) All of the above
Explanation: All three methods prevent the contact of iron with air and moisture, thus preventing rusting. However, for cooking utensils, applying a coating of zinc (galvanization) or seasoning with oil is most practical.
Q3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
(a) Calcium (b) Carbon (c) Silicon (d) Iron
Answer: (a) Calcium
Explanation: Calcium reacts with oxygen to form calcium oxide (CaO), also known as quickite. CaO has a high melting point (2572°C) and dissolves in water to form calcium hydroxide Ca(OH)₂. Carbon and silicon form covalent oxides with low melting points, and iron oxide is insoluble in water.
Important Concepts Summary
| Property | Metals | Non-metals |
|---|---|---|
| Physical State | Solid (except Mercury) | Solid, Liquid, or Gas |
| Lustre | Shiny | Dull (except Iodine, Diamond) |
| Malleability | Malleable | Non-malleable (Brittle) |
| Ductility | Ductile | Non-ductile |
| Conductivity | Good conductors | Poor conductors (except Graphite) |
| Oxides | Basic oxides | Acidic oxides |
Reactivity Series of Metals
The arrangement of metals in decreasing order of their reactivity:
K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Hg > Ag > Au > Pt
Memory Tip: “King Nathan Caught Many Ants Zipping Fast, Now Silly People Have Copper Mercury Silver And Gold Platinum”
Key Takeaways
- Metals are lustrous, malleable, ductile, and good conductors of heat and electricity
- Non-metals are generally brittle and poor conductors
- Metals react with oxygen to form basic oxides; non-metals form acidic oxides
- More reactive metals displace less reactive metals from their salt solutions
- Metals are extracted from ores by reduction processes
- Corrosion can be prevented by galvanization, painting, or oiling
- Alloys are homogeneous mixtures of metals that have improved properties
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