Physical Science Classes VI-X for School Assistants and TET Paper 2A · Chapter 9

Metals, Non-metals, Metallurgy and Carbon Compounds

What to remember

Metals are lustrous, malleable, ductile conductors that form basic oxides and positive ions; non-metals are brittle, poor conductors that form acidic oxides. Metals are extracted from ores by a method chosen from their position in the reactivity series.
Carbon has four valence electrons and forms covalent bonds; tetravalency and catenation give the huge number of carbon compounds, grouped in homologous series by functional groups.
Key reactions to know: combustion, oxidation of ethanol, esterification, saponification, addition (hydrogenation) and substitution.

Metals and non-metals: properties

Property	Metals	Non-metals
Lustre	Shiny	Dull (iodine and graphite are shiny)
Hardness	Hard (Na, K are soft)	Soft (diamond is hardest)
Malleable and ductile	Yes	No, brittle
Conductivity	Good conductors of heat and electricity	Poor (graphite conducts)
Melting point	Usually high (Ga, Cs low)	Usually low
Oxides	Basic or amphoteric	Acidic or neutral
State	Solid (mercury is liquid)	Solid, liquid (bromine) or gas

Amphoteric oxides react with both acids and bases: Al2O3, ZnO.
Silver is the best conductor of electricity; lead and mercury are poor conductors among metals. Gold and platinum are very unreactive.
Reactions of metals:
With oxygen: metal + O2 gives metal oxide (4Na + O2 gives 2Na2O). Sodium and potassium are stored under kerosene because they react vigorously with air.
With water: 2Na + 2H2O gives 2NaOH + H2. Magnesium reacts with hot water; aluminium, iron and zinc react with steam to give oxide and hydrogen.
With dilute acid: Zn + 2HCl gives ZnCl2 + H2. Copper, silver and gold do not release hydrogen from dilute acids.
Displacement: a more reactive metal displaces a less reactive one from solution (Fe + CuSO4 gives FeSO4 + Cu).
Reactivity series (high to low): K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au.
Aqua regia: 3 parts concentrated HCl to 1 part concentrated HNO3; dissolves gold and platinum.
Ionic compounds form between metals and non-metals; they have high melting points and conduct when molten or dissolved.

Metallurgy

Terms: mineral (natural compound of a metal), ore (mineral from which a metal can be extracted profitably), gangue (earthy impurities in an ore), flux (substance added to remove gangue as slag; e.g. limestone for silica), slag (flux + gangue).

Metal	Main ore	Formula
Sodium	Rock salt	NaCl
Aluminium	Bauxite	Al2O3·2H2O
Iron	Haematite	Fe2O3
Copper	Copper pyrites	CuFeS2
Zinc	Zinc blende	ZnS
Mercury	Cinnabar	HgS
Lead	Galena	PbS

Steps of extraction:

1. Concentration (ore dressing): hydraulic washing (heavy ores), magnetic separation (magnetic ore from non-magnetic), froth flotation (sulphide ores), leaching (chemical dissolving, used for bauxite).
2. Conversion to oxide: *calcination* is heating a carbonate ore in limited or no air (ZnCO3 gives ZnO + CO2). *Roasting* is heating a sulphide ore in excess air (2ZnS + 3O2 gives 2ZnO + 2SO2).
3. Reduction: by carbon (coke) for metals in the middle of the series (ZnO + C gives Zn + CO). Highly reactive metals (Na, Ca, Mg, Al) are obtained by electrolysis of molten compounds. Mercury and copper can be got by simply heating their sulphides in air.
4. Refining: electrolytic refining is the most common. Impure metal is the anode, pure metal is the cathode and a salt solution of the metal is the electrolyte (copper is refined this way).
By position: top metals (K to Al) by electrolysis of molten salts; middle metals (Zn, Fe, Pb) by reducing the oxide with carbon; bottom metals (Hg, Ag, Au) by heating or occur free.
Thermite reaction: Fe2O3 + 2Al gives Al2O3 + 2Fe with a large release of heat (molten iron used to weld rail tracks).
Alumina is electrolysed in molten cryolite (Hall-Heroult process); the cathode is graphite and aluminium collects at the bottom.
Blast furnace: iron ore, coke and limestone. Iron oxide is reduced by carbon monoxide.
Corrosion: slow attack on metals by air and moisture. Rusting of iron needs both oxygen and water (rust is hydrated iron(III) oxide, Fe2O3·xH2O). Copper turns green (basic copper carbonate) and silver turns black (silver sulphide).
Prevention: painting, oiling, galvanisation (zinc coating), tin plating, chrome plating, anodising (aluminium) and alloying.
Alloys: homogeneous mixtures of metals (or a metal and non-metal). Brass = Cu + Zn; bronze = Cu + Sn; solder = Pb + Sn (low melting point); stainless steel = Fe + Cr + Ni + C; amalgam is an alloy with mercury.

Carbon and its compounds

Bonding: carbon forms four covalent bonds. It cannot easily gain or lose four electrons, so it shares them.
Catenation: carbon atoms link to each other in long chains, branched chains and rings. Tetravalency: carbon bonds with H, O, N, S and halogens.
Allotropes: diamond (each C bonded to four others, hardest natural substance, non-conductor, sp3), graphite (layers of hexagons, slippery, conducts electricity, sp2, used as lubricant and in pencils), fullerene (C60 football-shaped molecule).
Properties of covalent compounds: low melting/boiling points, poor conductivity, often soluble in organic solvents.
Hydrocarbons: saturated (alkanes, single bonds, CnH2n+2), unsaturated (alkenes CnH2n with a double bond; alkynes CnH2n-2 with a triple bond).
Homologous series: a family of compounds with the same functional group and general formula; successive members differ by CH2 (14 mass units). Properties vary gradually.

Carbons	Alkane	Alkene	Alkyne
1	Methane CH4	-	-
2	Ethane C2H6	Ethene C2H4	Ethyne C2H2
3	Propane C3H8	Propene C3H6	Propyne C3H4
4	Butane C4H10	Butene C4H8	Butyne C4H6

Prefixes: 1 meth, 2 eth, 3 prop, 4 but, 5 pent, 6 hex.

Functional groups: alcohol -OH (suffix -ol), aldehyde -CHO (-al), ketone >C=O (-one), carboxylic acid -COOH (-oic acid), halo group -Cl/-Br.
Isomerism: compounds with the same molecular formula but different structures. Butane (C4H10) has two isomers: n-butane and isobutane.
Worked example: an alkane with 8 carbons is C8H18 (2n + 2 = 18). Molar mass of ethanol C2H5OH = 24 + 6 + 16 = 46 g/mol. The alkane with molar mass 44 is propane (36 + 8).

Important reactions

Combustion: CH4 + 2O2 gives CO2 + 2H2O + heat. Saturated hydrocarbons burn with a clean blue flame; unsaturated ones burn with a yellow sooty flame.
Oxidation: ethanol with alkaline KMnO4 or acidified potassium dichromate gives ethanoic acid.
Addition (hydrogenation): unsaturated hydrocarbon + H2 with nickel catalyst gives saturated (vegetable oil to vanaspati ghee).
Substitution: alkane + Cl2 in sunlight replaces H with Cl (CH4 + Cl2 gives CH3Cl + HCl).
Ethanol: a colourless liquid; dehydrated by conc. H2SO4 at 443 K to give ethene. Ethanol reacts with sodium to give sodium ethoxide and hydrogen. Ethanol is toxic as methylated spirit; "denatured alcohol" has methanol or a dye added. Drinking methanol can cause blindness.
Ethanoic acid (acetic acid): pure form freezes at about 290 K and is called glacial acetic acid; vinegar is 5 to 8 percent acetic acid in water. It turns blue litmus red and releases CO2 with sodium carbonate and sodium hydrogencarbonate.
Esterification: acid + alcohol with conc. H2SO4 gives ester + water (sweet fruity smell). CH3COOH + C2H5OH gives CH3COOC2H5 + H2O.
Saponification: ester + NaOH gives alcohol + sodium salt of the acid (soap).
Soaps and detergents: soap is the sodium or potassium salt of a long-chain fatty acid. A soap molecule has a hydrophilic head and hydrophobic tail and forms micelles that trap oil. Soap forms scum with hard water (Ca and Mg ions); synthetic detergents (sulphonates) do not.

Classroom angle

Show conductivity of graphite vs diamond with a simple battery-bulb circuit; show displacement with an iron nail in copper sulphate; let students rust nails in four test tubes (dry air, water without air, water with air, oil) to prove both air and water are needed.

Exam traps

Calcination is for carbonate ores in no or little air; roasting is for sulphide ores in excess air.
Mercury is a liquid metal; bromine is a liquid non-metal.
Graphite is a non-metal that conducts; diamond does not.
Alkenes have CnH2n; alkynes have CnH2n-2.
Brass is Cu + Zn; bronze is Cu + Sn.
Rusting needs both oxygen and water; galvanisation uses zinc.
Aluminium and zinc oxides are amphoteric, not basic.
Hydrogenation needs a nickel catalyst; esterification needs conc. H2SO4.
Saponification gives soap plus an alcohol (glycerol for fats).
Soap does not lather well in hard water; detergents do.

One-liners

1. Sodium and potassium are stored under kerosene.
2. Silver is the best electrical conductor.
3. Haematite is an iron ore (Fe2O3); bauxite is an aluminium ore.
4. Cinnabar is the ore of mercury.
5. Aqua regia dissolves gold and platinum.
6. Thermite uses aluminium to reduce iron oxide.
7. Solder is an alloy of lead and tin.
8. Diamond is the hardest natural substance; graphite is slippery.
9. C60 is called buckminsterfullerene.
10. Methane is the simplest alkane; ethyne the simplest alkyne.
11. Glacial acetic acid freezes near 290 K.
12. Soaps are sodium or potassium salts of fatty acids.

Practice questions

The only metal that is liquid at room temperature is
1. sodium
2. lead
3. gallium
4. mercury
Answer
D. mercury
Mercury melts at about -39 °C. (Gallium melts just above room temperature.)
The best conductor of electricity among metals is
1. copper
2. gold
3. silver
4. aluminium
Answer
C. silver
Silver has the highest electrical conductivity.
The chief ore of aluminium is
1. cinnabar
2. bauxite
3. galena
4. haematite
Answer
B. bauxite
Bauxite is Al2O3·2H2O.
Cinnabar is an ore of
1. zinc
2. mercury
3. copper
4. lead
Answer
B. mercury
Cinnabar is mercury sulphide, HgS.
Brass is an alloy of
1. copper and tin
2. lead and tin
3. iron and carbon
4. copper and zinc
Answer
D. copper and zinc
Brass = Cu + Zn; bronze = Cu + Sn.
Solder is an alloy of
1. tin and copper
2. iron and nickel
3. lead and tin
4. copper and zinc
Answer
C. lead and tin
Solder has a low melting point and is used to join wires.
The hardest natural substance is
1. diamond
2. quartz
3. graphite
4. fullerene
Answer
A. diamond
Each carbon in diamond is bonded to four others in a rigid network.
The functional group of alcohols is
1. -COOH
2. -CHO
3. -Cl
4. -OH
Answer
D. -OH
Alcohols contain the hydroxyl group.
The molecular formula of ethyne is
1. C3H4
2. C2H2
3. C2H4
4. C2H6
Answer
B. C2H2
Ethyne is the simplest alkyne, CnH2n-2 with n = 2.
Aqua regia, which dissolves gold, is a mixture of conc. HCl and conc. HNO3 in the ratio
1. 1 : 1
2. 2 : 1
3. 3 : 1
4. 1 : 3
Answer
C. 3 : 1
Three parts HCl to one part HNO3.
Sodium and potassium are stored under kerosene because they
1. are radioactive
2. are non-metals
3. react vigorously with air and moisture
4. are heavier than water
Answer
C. react vigorously with air and moisture
They would catch fire in air.
The catalyst commonly used for hydrogenation of vegetable oils is
1. nickel
2. iron
3. platinum wire only
4. copper oxide
Answer
A. nickel
Finely divided nickel adds H2 across the C=C bonds.
Roasting is the process of heating a
1. carbonate ore in limited air
2. sulphide ore in excess air
3. metal in nitrogen
4. oxide ore with carbon
Answer
B. sulphide ore in excess air
2ZnS + 3O2 gives 2ZnO + 2SO2.
Calcination is the heating of
1. a metal with a salt solution
2. an oxide ore with aluminium
3. a sulphide ore in excess air
4. a carbonate ore in limited or no air
Answer
D. a carbonate ore in limited or no air
ZnCO3 gives ZnO + CO2.
Sodium is extracted by electrolysis of its molten salt because it
1. is a poor conductor
2. has a very high melting point
3. is a non-metal
4. is a highly reactive metal high in the reactivity series
Answer
D. is a highly reactive metal high in the reactivity series
Carbon cannot reduce the oxides of highly reactive metals.
Graphite conducts electricity because
1. it contains water
2. each carbon has a free (delocalised) electron in its layer
3. it has ionic bonds
4. it is a metal
Answer
B. each carbon has a free (delocalised) electron in its layer
sp2 carbons leave one electron free to move.
Rusting of iron requires
1. only oxygen
2. only water
3. both oxygen and water
4. only carbon dioxide
Answer
C. both oxygen and water
Iron in dry air or in boiled water without air does not rust.
Galvanisation is the coating of iron with
1. zinc
2. chromium
3. tin
4. copper
Answer
A. zinc
Zinc protects iron even if the coating is scratched.
Soap does not lather well in hard water because
1. it forms insoluble scum with calcium and magnesium ions
2. hard water is basic
3. it becomes acidic
4. it dissolves completely
Answer
A. it forms insoluble scum with calcium and magnesium ions
Detergents do not form scum.
Unsaturated hydrocarbons burn with a sooty yellow flame because
1. they contain oxygen
2. they are metals
3. they contain nitrogen
4. their carbon percentage is high and burning is incomplete
Answer
D. their carbon percentage is high and burning is incomplete
More carbon needs more air than is available.
In the thermite reaction the reducing agent is
1. zinc
2. carbon
3. aluminium
4. hydrogen
Answer
C. aluminium
Fe2O3 + 2Al gives Al2O3 + 2Fe.
An amphoteric oxide is
1. CaO
2. Al2O3
3. Na2O
4. CO2
Answer
B. Al2O3
Aluminium oxide reacts with both acids and bases.
Heating a fat with sodium hydroxide to make soap is called
1. esterification
2. saponification
3. fermentation
4. hydrogenation
Answer
B. saponification
Fat + NaOH gives soap + glycerol.
The general formula of alkenes is
1. CnH2n
2. CnH2n-2
3. CnHn
4. CnH2n+2
Answer
A. CnH2n
One double bond lowers hydrogen count by two from the alkane.
The molecular formula of the alkane with 6 carbon atoms is
1. C6H12
2. C6H10
3. C6H14
4. C6H16
Answer
C. C6H14
2n + 2 = 14.
The molecular formula of the alkyne with 4 carbon atoms is
1. C4H8
2. C4H4
3. C4H10
4. C4H6
Answer
D. C4H6
2n - 2 = 6.
The molar mass of ethanol (C2H5OH; C = 12, H = 1, O = 16) is
1. 44 g/mol
2. 32 g/mol
3. 60 g/mol
4. 46 g/mol
Answer
D. 46 g/mol
24 + 6 + 16 = 46.
A hydrocarbon of the alkene family has 10 hydrogen atoms. Its formula is
1. C5H10
2. C4H10
3. C10H10
4. C5H12
Answer
A. C5H10
CnH2n with 2n = 10 gives n = 5.
The difference in molecular mass between successive members of a homologous series is
1. 28 u
2. 14 u
3. 12 u
4. 16 u
Answer
B. 14 u
Each member differs by a CH2 unit: 12 + 2 = 14.
The mass of 2 moles of methane (C = 12, H = 1) is
1. 64 g
2. 16 g
3. 32 g
4. 18 g
Answer
C. 32 g
Molar mass is 16 g, so 2 mol = 32 g.
The percentage of carbon by mass in methane (C = 12, H = 1) is
1. 75%
2. 50%
3. 80%
4. 25%
Answer
A. 75%
12/16 × 100 = 75.
The volume of oxygen needed for complete combustion of 5 L of methane at the same temperature and pressure is
1. 2.5 L
2. 10 L
3. 15 L
4. 5 L
Answer
B. 10 L
CH4 + 2O2 gives CO2 + 2H2O; volume ratio 1 : 2.
The moles of CO2 formed by complete combustion of 1 mol of ethane are
1. 1
2. 3
3. 2
4. 4
Answer
C. 2
C2H6 has two carbon atoms, each giving one CO2.
Which of the statements is/are correct? 1. Calcination is done for carbonate ores in limited air. 2. Roasting is done for sulphide ores in excess air.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are correct.
Which of the statements is/are correct? 1. Graphite conducts electricity. 2. Diamond conducts electricity.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Diamond has no free electrons.
Which of the statements is/are correct? 1. Brass is an alloy of copper and tin. 2. Bronze is an alloy of copper and zinc.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
D. Neither 1 nor 2
Brass is Cu + Zn and bronze is Cu + Sn.
Which of the statements is/are correct? 1. Ionic compounds conduct electricity in the solid state. 2. Ionic compounds have high melting points.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Ionic solids do not conduct because ions cannot move.
Which of the statements is/are correct? 1. Saturated hydrocarbons burn with a clean flame. 2. Unsaturated hydrocarbons burn with a sooty flame.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are correct.
Which of the statements is/are correct? 1. In electrolytic refining the impure metal is the anode. 2. The pure metal collects at the anode.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Pure metal deposits at the cathode.
Which of the statements is/are correct? 1. Soaps are sodium or potassium salts of fatty acids. 2. Detergents form scum with hard water.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Detergents do not form scum.
Which of the statements is/are correct? 1. Ethanol reacts with sodium to give hydrogen. 2. Ethanoic acid does not react with sodium carbonate.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Ethanoic acid gives CO2 with carbonates.
Which of the statements is/are correct? 1. Mercury is a metal that is liquid at room temperature. 2. Bromine is a non-metal that is liquid at room temperature.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are correct.
Which of the statements is/are correct? 1. Copper reacts with dilute HCl to release hydrogen. 2. A more reactive metal displaces a less reactive one from its salt solution.
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Copper is below hydrogen in the series and does not release H2.
Match the ore with the metal: (a) bauxite (b) galena (c) zinc blende (d) cinnabar; (i) Zn (ii) Hg (iii) Al (iv) Pb
1. a-iii, b-iv, c-ii, d-i
2. a-i, b-iv, c-iii, d-ii
3. a-iv, b-iii, c-i, d-ii
4. a-iii, b-iv, c-i, d-ii
Answer
D. a-iii, b-iv, c-i, d-ii
Bauxite-Al, galena-Pb, zinc blende-Zn, cinnabar-Hg.
Match the functional group with the name of the family: (a) -CHO (b) -COOH (c) -OH (d) >C=O; (i) ketone (ii) alcohol (iii) aldehyde (iv) carboxylic acid
1. a-iv, b-iii, c-ii, d-i
2. a-ii, b-iv, c-iii, d-i
3. a-iii, b-iv, c-i, d-ii
4. a-iii, b-iv, c-ii, d-i
Answer
D. a-iii, b-iv, c-ii, d-i
-CHO aldehyde, -COOH acid, -OH alcohol, >C=O ketone.

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1.The correct order of reactivity of the following metals is: K, Mg, Al, Zn
2.The element of a heater is made of-
3.The filament of an electric bulb is made of tungsten because it:
4.The filament of a light bulb is made up of tungsten, because of its ______.
5.The element, tellurium is a -
6.The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?
7.The extraction of metals from their ores is known as which of the following?
8.Substances that are broken down by biological processes are said to be:
9.Solder is an alloy of-
10.Solder is an alloy of ______.

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