(a) Compare the physical properties of metals and non-metals under the following heads: (i) physical state at room temperature, (ii) malleability and ductility, (iii) electrical conductivity.
(b) When magnesium burns in air, the ash formed dissolves in water to give a solution that turns red litmus blue. When sulphur burns and the fumes dissolve in water, the solution turns blue litmus red. What does this indicate about the general nature of metal and non-metal oxides? Write the equations for the formation of these oxides.
(c) Name one metal and one non-metal that are exceptions to these general rules for electrical conductivity.
Generated by claude-sonnet-4-6 · 2026-06-26 01:06 · grounding rag
Model Answer
(a)
| Property | Metals | Non-metals |
|---|---|---|
| Physical state | Mostly solids at room temperature (except mercury, which is liquid) | Solids or gases (except bromine, which is liquid) |
| Malleability & Ductility | Malleable (beaten into sheets) and ductile (drawn into wires) | Neither malleable nor ductile; they are brittle |
| Electrical conductivity | Good conductors of electricity | Bad conductors (insulators) |
(b)
When magnesium burns, it forms magnesium oxide (MgO), a basic oxide — its solution turns red litmus blue. When sulphur burns, it forms sulphur dioxide (SO₂), an acidic oxide — its solution turns blue litmus red.
This indicates that metal oxides are basic in nature and non-metal oxides are acidic in nature.
Equations:
$$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$
$$\text{S} + \text{O}_2 \rightarrow \text{SO}_2$$
(c)
- Exception in metals (poor conductor): Mercury (or lead)
- Exception in non-metals (good conductor): Graphite (an allotrope of carbon)
Source: Chapter 3, Sections 3.1 and 3.2.1
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Explanation
- For part (a), the table format earns full marks efficiently — state, malleability/ductility, and conductivity are the three specific heads asked.
- For part (b), examiners expect you to explicitly state the conclusion: metal oxides = basic; non-metal oxides = acidic. The two balanced equations are mandatory.
- For part (c), graphite (not just "carbon") is the expected answer for the non-metal exception, as stated in the textbook. Mercury is the most common metal exception for conductivity (though lead is also acceptable). The textbook specifically names graphite as the non-metal exception.