This MCQ module is based on: Physical and Chemical Properties of Metals and Non-metals
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Physical and Chemical Properties of Metals and Non-metals
🎓 Class 10
Science
CBSE
Theory
Ch 3 — Metals and Non-metals
⏱ ~23 min
🌐 Language: [gtranslate]
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[myaischool_lt_science_assessment grade_level="class_10" science_domain="chemistry" difficulty="intermediate"]
Introduction: The Variety of Elements
Out of the 118 elements that chemists have discovered so far, each element is placed into one of three broad families based on how it behaves physically and chemically: metals, non-metals, and metalloids. In this chapter we explore how the first two groups differ in their physical appearance, how they react with oxygen, water, acids and salt solutions, and how chemists put this knowledge to work in everyday life.
3.1 Physical Properties
Physical Properties of Metals
- Metallic lustre: Freshly cut metal surfaces shine.
- Hardness: Most metals are hard, but sodium and potassium are so soft they can be cut with a knife.
- Malleability: They can be hammered into thin sheets (gold and silver are the most malleable).
- Ductility: They can be drawn into thin wires (1 g of gold yields about 2 km of wire!).
- Good conductors of heat and electricity: Silver and copper top the list; mercury and lead are poor among metals.
- Sonorous: Produce a ringing sound when struck (reason school bells are made of metal).
- High melting/boiling points.
- Exceptions: Mercury is the only metal that is liquid at room temperature; gallium and caesium melt just above room temperature (gallium melts in your palm at 30°C).
Physical Properties of Non-metals
- No lustre: Generally dull (iodine is the lustrous exception).
- Brittle in the solid state.
- Poor conductors of heat and electricity (graphite, a form of carbon, is the conducting exception).
- Low melting/boiling points (diamond, an allotrope of carbon, is the exception with a very high melting point).
- Exist in all three states: solids (S, P, C), liquid (Br) and gases (H2, O2, N2, Cl2).
3.2 Chemical Properties of Metals
3.2.1 Reaction with Oxygen — Formation of Basic Oxides
Most metals combine with oxygen on heating to give a corresponding oxide:
Metal + O2 → Metal oxide
\(4\text{Na}(s) + \text{O}_2(g) \rightarrow 2\text{Na}_2\text{O}(s)\)
\(2\text{Mg}(s) + \text{O}_2(g) \xrightarrow{\Delta} 2\text{MgO}(s)\) (dazzling white flame)
\(2\text{Cu}(s) + \text{O}_2(g) \xrightarrow{\Delta} 2\text{CuO}(s)\) (black copper(II) oxide)
\(4\text{Al}(s) + 3\text{O}_2(g) \rightarrow 2\text{Al}_2\text{O}_3(s)\)
Sodium is so reactive towards atmospheric oxygen that it spontaneously catches fire in air — which is why it is stored submerged under kerosene oil.
Most metallic oxides are basic. However, some — notably aluminium oxide (Al2O3) and zinc oxide (ZnO) — react with both acids and bases, behaving as amphoteric oxides:
\(\text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O}\)
\(\text{Al}_2\text{O}_3 + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + \text{H}_2\text{O}\)
Anodising: Aluminium naturally forms a thin Al2O3 layer on its surface which resists further corrosion. In anodising, this protective layer is made artificially thick by electrolysis, using Al as anode in dilute H2SO4. The thick oxide coat can be dyed and is used on window frames and aircraft bodies.
Activity 3.9 — Is Magnesium Oxide Acidic or Basic?L3 Apply
Predict: When the white ash of burnt magnesium is dissolved in water, will the solution turn blue litmus red or red litmus blue?
- Clean a piece of magnesium ribbon with sandpaper and ignite it using tongs.
- Collect the white ash (MgO) on a watch glass.
- Add a few drops of water and stir — Mg(OH)2 solution forms.
- Dip both blue and red litmus papers.
Observation: Red litmus turns blue — the solution is basic.
\(\text{MgO}(s) + \text{H}_2\text{O}(l) \rightarrow \text{Mg(OH)}_2(aq)\)
Conclusion: Metal oxides are typically basic in nature.
3.2.2 Reaction with Water
Metals differ enormously in how they react (or refuse to react) with water. The more reactive the metal, the more violently it displaces hydrogen from water.
| Metal | Reacts with | Equation |
|---|---|---|
| Potassium (K) | Cold water — violently, catches fire | \(2\text{K}+2\text{H}_2\text{O}\rightarrow 2\text{KOH}+\text{H}_2+\text{heat}\) |
| Sodium (Na) | Cold water — vigorous | \(2\text{Na}+2\text{H}_2\text{O}\rightarrow 2\text{NaOH}+\text{H}_2\) |
| Calcium (Ca) | Cold water — floats on H2 bubbles | \(\text{Ca}+2\text{H}_2\text{O}\rightarrow \text{Ca(OH)}_2+\text{H}_2\) |
| Magnesium (Mg) | Hot water only | \(\text{Mg}+2\text{H}_2\text{O}\rightarrow \text{Mg(OH)}_2+\text{H}_2\) |
| Iron (Fe) | Steam only, reversible | \(3\text{Fe}+4\text{H}_2\text{O}\rightarrow \text{Fe}_3\text{O}_4+4\text{H}_2\) |
| Al, Zn | Steam | \(2\text{Al}+3\text{H}_2\text{O}\rightarrow \text{Al}_2\text{O}_3+3\text{H}_2\) |
| Cu, Ag, Au | No reaction | — |
Why Ca floats but Na doesn't catch fire: Ca reacts less violently than Na, so the heat liberated is insufficient to ignite the hydrogen. The H2 bubbles stick to the metal surface and lift it to the water's surface.
3.2.3 Reaction with Dilute Acids
Metals more reactive than hydrogen displace it from dilute HCl or H2SO4:
Metal + dilute acid → Salt + H2↑
\(\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2\uparrow\)
\(\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2\uparrow\)
\(\text{Fe} + 2\text{HCl} \rightarrow \text{FeCl}_2 + \text{H}_2\uparrow\)
Cu + HCl → No reaction (Cu lies below H in the activity series)
The evolved gas gives the familiar pop test with a burning match.
Why HNO3 usually does NOT give H2: Nitric acid is a strong oxidising agent — it oxidises the hydrogen produced to water and itself gets reduced to NO2, NO, N2O or NH4NO3 depending on concentration. Exception: Very dilute HNO3 reacts with Mg and Mn to liberate H2.
3.2.4 How Metals React with Salt Solutions
A more reactive metal displaces a less reactive metal from its salt solution. This is the principle of displacement reactions:
\(\text{Fe}(s) + \text{CuSO}_4(aq) \rightarrow \text{FeSO}_4(aq) + \text{Cu}(s)\)
Blue copper sulphate solution gradually turns pale green as iron sulphate is formed, and a brown copper deposit collects on the iron nail.
\(\text{Zn}(s) + \text{CuSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Cu}(s)\)
Cu + FeSO4 → No reaction (Cu less reactive than Fe)
Worked Examples
Example 1 — Balance the reaction of aluminium with dilute sulphuric acid.
Solution: Unbalanced: Al + H2SO4 → Al2(SO4)3 + H2.
Balance Al: place 2 before Al. Balance SO4: place 3 before H2SO4 (giving 6 H). Balance H: place 3 before H2.
\(2\text{Al} + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{H}_2\)
Example 2 — Why is sodium stored under kerosene oil?
Solution: Sodium is so reactive that it ignites spontaneously when exposed to air (reacting with O2 and moisture). Kerosene seals it from air and moisture, preventing the dangerous exothermic reaction.
Example 3 — Predict whether Cu can displace Ag from AgNO3.
Solution: Copper lies above silver in the reactivity series, so it does displace silver. The blue colour of Cu2+ appears and shiny silver metal deposits on the copper wire.
\(\text{Cu}(s) + 2\text{AgNO}_3(aq) \rightarrow \text{Cu(NO}_3)_2(aq) + 2\text{Ag}(s)\)
Example 4 — Write the equation for potassium with water and explain the observation.
Solution: \(2\text{K}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{KOH}(aq) + \text{H}_2(g) + \text{heat}\). The reaction is so exothermic that the hydrogen bursts into a lilac-coloured flame; the solution becomes strongly alkaline (turns red litmus blue).
Example 5 — Complete: Fe + CuSO4 → ? Describe what you would see.
Solution: \(\text{Fe}+\text{CuSO}_4\rightarrow \text{FeSO}_4+\text{Cu}\). The blue colour of CuSO4 slowly fades to pale green (FeSO4) and a brownish-red deposit of Cu forms on the nail, since Fe is more reactive than Cu.
Interactive: Will It React? L3 Apply
Pick a metal and a reagent. Click to see whether they react, and the equation.
Competency-Based Questions
A student takes four test tubes containing dilute HCl and drops a small piece of Mg, Zn, Fe and Cu (one metal per tube). She observes the speed of bubbling.
Q1. L2 Understand In which test tube will she NOT see any bubbles of gas? (1 mark)
Answer: D. Cu. Copper is less reactive than hydrogen, so it cannot displace H2 from dilute HCl.
Q2. L3 Apply Write the balanced equations for the reaction of Mg and Zn with dilute HCl. (2 marks)
\(\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2\uparrow\)
\(\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2\uparrow\)
\(\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2\uparrow\)
Q3. L4 Analyse Why does the magnesium ribbon's reaction produce bubbles faster than the iron filing's? (2 marks)
Magnesium is considerably more reactive than iron. It lies much higher in the activity series, so it loses electrons more readily and reacts with H+ ions in acid at a much faster rate than iron does.
Q4. L5 Evaluate A student claims that since Cu does not react with dilute HCl, it also cannot react with any acid. Is this correct? Justify. (3 marks)
The claim is incorrect. Cu does react with concentrated HNO3 and concentrated H2SO4 (which act as oxidising agents), producing NO2/SO2 respectively. The reaction of Cu with dilute non-oxidising acids is prevented because Cu cannot displace H2, not because it reacts with no acid at all.
Q5. L3 Apply State two exceptions to the rule that "metals are solids at room temperature." (1 mark)
Mercury (Hg) is liquid at room temperature. Gallium (Ga) and caesium (Cs) melt just above room temperature — gallium melts in the palm of a hand.
Assertion-Reason Questions
Assertion (A): Sodium is kept immersed in kerosene oil.
Reason (R): Sodium reacts vigorously with oxygen and moisture of air, catching fire.
A. Both true, and R correctly explains A.
Assertion (A): Aluminium oxide is an amphoteric oxide.
Reason (R): It reacts only with acids and not with bases.
C. A is true (Al2O3 is amphoteric). R is false — it reacts with both acids and bases.
Assertion (A): Nitric acid with Mg gives hydrogen gas.
Reason (R): HNO3 is a strong oxidising agent and normally oxidises the H2 produced.
B. Both statements are true individually — very dilute HNO3 reacts with Mg (and Mn) giving H2. However, R describes the general behaviour of HNO3, which is why A is considered an exception, not the rule. Hence R does not explain A.
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