General Science Supplement for Forest Beat Officer · Chapter 5

Metals, Non-metals and Natural Resources

What to remember

Metals lose electrons and form positive ions; non-metals gain electrons and form negative ions. Metals are shiny, malleable, ductile and good conductors. Non-metals are mostly brittle and poor conductors (graphite is the main exception).
The reactivity series decides how a metal is extracted: very reactive metals by electrolysis, middle metals by reduction of oxides with carbon, and the least reactive metals occur free or are reduced by heating.
Fossil fuels (coal, petroleum, natural gas) are exhaustible natural resources; saving them and using alternatives is a basic part of resource management.

Physical and chemical properties

Metals are lustrous, hard (except sodium and potassium, which can be cut with a knife), sonorous and have high melting points. Gallium and caesium melt at very low temperatures. Mercury is the only metal that is liquid at room temperature; bromine is the only liquid non-metal. Silver is the best conductor of heat and electricity, followed by copper. Lead and mercury are poor conductors among metals. Gold and silver are the most malleable and ductile.

Non-metals such as carbon (diamond), sulphur and phosphorus are brittle and dull. Diamond is the hardest natural substance and does not conduct electricity. Graphite conducts electricity because it has free electrons. Iodine is a lustrous non-metal.

Chemical behaviour of metals:

Metal + oxygen gives a metal oxide. Metal oxides are basic. Some oxides such as aluminium oxide and zinc oxide react with both acids and bases. They are called amphoteric oxides.
Metal + water: sodium and potassium react violently with cold water and give hydrogen. Calcium reacts less violently. Magnesium reacts with hot water. Aluminium, zinc and iron react with steam. Copper, silver and gold do not react.
Metal + dilute acid gives a salt and hydrogen gas. Copper does not release hydrogen from dilute acid.
A more reactive metal displaces a less reactive metal from its salt solution. For example, iron displaces copper from copper sulphate solution.

Non-metal oxides are acidic (for example CO₂, SO₂) or neutral (for example CO, water, N₂O). Non-metals do not react with water or dilute acids to give hydrogen.

Reactivity series

From most to least reactive: K, Na, Ca, Mg, Al, Zn, Fe, Pb, [H], Cu, Hg, Ag, Au. Hydrogen is placed in the series for comparison only. Metals above hydrogen displace hydrogen from dilute acids.

Ionic compounds are formed by the transfer of electrons from a metal to a non-metal. They are hard solids, have high melting and boiling points, dissolve in water and conduct electricity in the molten state or in solution, but not as solids.

Group	Metals	Method of extraction
Highly reactive	K, Na, Ca, Mg, Al	Electrolysis of the molten chloride or oxide
Moderately reactive	Zn, Fe, Pb	Reduction of the oxide with carbon (coke) or carbon monoxide
Low reactivity	Cu, Hg, Ag, Au	Heating the ore, or found free in nature

Extraction of metals

A mineral is a natural substance containing a metal. An ore is a mineral from which the metal can be extracted profitably. The earthy impurities in an ore are called gangue.

Steps: concentration of the ore, conversion to the oxide, reduction to the metal, and refining.

Roasting: heating a sulphide ore strongly in excess air to give the oxide. Example: 2ZnS + 3O₂ → 2ZnO + 2SO₂.
Calcination: heating a carbonate ore in limited air to give the oxide. Example: ZnCO₃ → ZnO + CO₂.
Reduction: ZnO + C → Zn + CO.
Thermite reaction: aluminium reduces iron oxide with a huge amount of heat, giving molten iron used to weld railway tracks. Fe₂O₃ + 2Al → 2Fe + Al₂O₃.
Electrolytic refining: the impure metal is the anode and a thin strip of pure metal is the cathode. Pure metal collects on the cathode. Impurities settle below the anode as anode mud.
Aluminium is obtained from bauxite (purified to alumina, then electrolysed in molten cryolite). Sodium is obtained from molten sodium chloride.

Common ores: bauxite (aluminium), haematite and magnetite (iron), cinnabar (mercury), galena (lead), zinc blende (zinc), copper pyrites (copper), rock salt (sodium chloride).

Alloys and corrosion

An alloy is a homogeneous mixture of a metal with other metals or non-metals. Alloys are harder, stronger and more resistant to corrosion than the pure metal.

Alloy	Main components	Use
Brass	Copper + zinc	Utensils, instruments
Bronze	Copper + tin	Statues, medals
Stainless steel	Iron + chromium + nickel + carbon	Cutlery, surgical tools
Solder	Lead + tin	Joining wires
Amalgam	Mercury + another metal	Dental fillings

Pure gold is 24 carat. 22 carat gold is an alloy that is about 91.6 percent gold. Iron becomes steel when a small, controlled amount of carbon is added.

Corrosion is the slow attack on a metal by air, moisture or chemicals. Rusting needs both oxygen and water. Rust is hydrated iron(III) oxide, Fe₂O₃·xH₂O. Silver turns black (silver sulphide), copper turns green (basic copper carbonate), and aluminium forms a protective oxide layer.

Prevention: painting, oiling, galvanisation (coating iron with zinc), tin plating, chrome plating, alloying and sacrificial protection (a more reactive metal such as magnesium or zinc is attached to iron and corrodes instead of it).

Important non-metals

Carbon: allotropes are diamond, graphite and fullerene (for example C₆₀). Graphite is soft, slippery and used in pencil leads and as a lubricant.
Sulphur: yellow solid used for sulphuric acid, gunpowder and vulcanisation of rubber.
Phosphorus: white phosphorus is very reactive and stored under water. Red phosphorus is stable and used on matchboxes.
Nitrogen: about 78 percent of air by volume. Oxygen is about 21 percent. Argon is the most abundant noble gas in air.
Halogens: fluorine, chlorine, bromine, iodine. Chlorine is used to disinfect drinking water.
Noble gases: helium, neon, argon, krypton, xenon. They are inert. Helium is used in balloons and neon in advertising lights.

Natural resources

Natural resources are renewable (forests, water, sunlight, wind) or non-renewable (coal, petroleum, natural gas, minerals).

Coal is formed from buried plant matter over millions of years. Ranks by carbon content, lowest to highest: peat, lignite, bituminous, anthracite. Anthracite has the highest carbon content and heating value.
Petroleum is a mixture of hydrocarbons. It is separated by fractional distillation into petroleum gas, petrol, kerosene, diesel, lubricating oil and bitumen. The lightest fraction rises highest in the column.
Natural gas is mostly methane. It is used as CNG (compressed natural gas) for vehicles and as PNG (piped natural gas) for homes. LPG is mainly butane and propane.
Mica, bauxite, coal, iron ore, limestone and barytes are important minerals of India. Andhra Pradesh has a coastline, rivers, forests and mineral deposits, so mining must follow forest and environment rules.
Good practice: reduce, reuse, recycle, use public transport, and prefer solar and wind energy.

Exam traps

1. Mercury is the only liquid metal; bromine is the only liquid non-metal.
2. Silver conducts best, not copper; but copper is used in wires because it is cheaper.
3. Graphite conducts electricity; diamond does not, though both are pure carbon.
4. Roasting uses sulphide ores in excess air; calcination uses carbonate ores in limited air.
5. Ore and mineral are not the same: every ore is a mineral, but not every mineral is an ore.
6. Brass is copper and zinc; bronze is copper and tin.
7. Rusting needs both air and water; iron in dry air or in boiled water without air does not rust.
8. Galvanisation uses zinc, not tin.

One-liners

1. Sodium and potassium are stored under kerosene.
2. The most abundant metal in the Earth's crust is aluminium.
3. The most abundant element in the crust is oxygen.
4. Haematite is an ore of iron; bauxite is an ore of aluminium.
5. Cinnabar is an ore of mercury.
6. Thermite welding uses aluminium and iron oxide.
7. Anthracite is the best quality coal.
8. Rust is hydrated iron oxide.
9. Brass contains copper and zinc.
10. CNG is mainly methane.
11. White phosphorus is stored under water.
12. Aluminium oxide is an amphoteric oxide.

Worked examples

1. Percentage of iron in Fe₂O₃ (Fe = 56, O = 16): molar mass = 2 × 56 + 3 × 16 = 160. Iron = 112/160 = 70 percent.
2. Mass of aluminium oxide formed from 54 g of aluminium (Al = 27, Al₂O₃ = 102): 4Al + 3O₂ → 2Al₂O₃. 108 g Al gives 204 g oxide, so 54 g gives 102 g.
3. Mass of CO₂ from heating 100 g of calcium carbonate (CaCO₃ = 100, CO₂ = 44): CaCO₃ → CaO + CO₂. 100 g gives 44 g CO₂.
4. Mass of copper deposited when iron displaces it from copper sulphate: Fe + CuSO₄ → FeSO₄ + Cu. 56 g of iron gives 63.5 g of copper.

Practice questions

Which is the only metal that is liquid at room temperature?
1. Sodium
2. Gallium
3. Lead
4. Mercury
Answer
D. Mercury
Mercury is the only common metal that is liquid at room temperature.
Which metal is the best conductor of electricity?
1. Aluminium
2. Copper
3. Iron
4. Silver
Answer
D. Silver
Silver conducts best; copper is next but cheaper.
Thermite reaction is used for welding railway tracks. Which substance reduces iron oxide in it?
1. Aluminium
2. Carbon
3. Zinc
4. Hydrogen
Answer
A. Aluminium
Aluminium is more reactive than iron and displaces it from Fe2O3.
Which is the ore of aluminium?
1. Bauxite
2. Galena
3. Cinnabar
4. Haematite
Answer
A. Bauxite
Bauxite (hydrated aluminium oxide) is the main ore of aluminium.
Heating a sulphide ore strongly in excess air to convert it to oxide is called
1. smelting by electrolysis
2. calcination
3. distillation
4. roasting
Answer
D. roasting
Roasting uses excess air on sulphide ores; calcination uses limited air on carbonates.
Which alloy is made of copper and zinc?
1. Solder
2. Stainless steel
3. Brass
4. Bronze
Answer
C. Brass
Brass is copper plus zinc; bronze is copper plus tin.
Coating iron with a thin layer of zinc to prevent rusting is called
1. galvanisation
2. vulcanisation
3. calcination
4. anodising
Answer
A. galvanisation
Galvanisation uses zinc; zinc is more reactive and protects iron sacrificially.
Which allotrope of carbon conducts electricity?
1. Phosphorus
2. Diamond
3. Sulphur
4. Graphite
Answer
D. Graphite
Graphite has free electrons between its layers; diamond has none.
Which is the best quality coal with the highest carbon content?
1. Peat
2. Lignite
3. Bituminous
4. Anthracite
Answer
D. Anthracite
Carbon content rises: peat, lignite, bituminous, anthracite.
Rust is chemically
1. iron sulphide
2. hydrated iron(III) oxide
3. iron carbonate only
4. iron chloride
Answer
B. hydrated iron(III) oxide
Rust is Fe2O3.xH2O, formed in presence of air and water.
Which metal is stored under kerosene because it reacts vigorously with air and water?
1. Sodium
2. Gold
3. Copper
4. Silver
Answer
A. Sodium
Sodium and potassium are very reactive and are kept under kerosene.
Aluminium oxide reacts with both acids and bases. Such oxides are called
1. basic oxides
2. neutral oxides
3. amphoteric oxides
4. acidic oxides
Answer
C. amphoteric oxides
Al2O3 and ZnO show both acidic and basic behaviour.
Which metal is placed between zinc and lead in the reactivity series?
1. Silver
2. Iron
3. Copper
4. Sodium
Answer
B. Iron
Order: Zn, Fe, Pb, H, Cu.
In electrolytic refining of copper, the pure copper is deposited at the
1. anode
2. electrolyte surface
3. cathode
4. anode mud
Answer
C. cathode
Impure metal is the anode; pure metal deposits on the cathode and impurities form anode mud.
Which gas is released when a reactive metal such as zinc reacts with dilute hydrochloric acid?
1. Hydrogen
2. Carbon dioxide
3. Chlorine
4. Oxygen
Answer
A. Hydrogen
Metal + dilute acid gives a salt and hydrogen.
The more reactive metals such as sodium and aluminium are extracted from their ores by
1. heating in air
2. reduction with carbon
3. simple roasting
4. electrolysis of molten compounds
Answer
D. electrolysis of molten compounds
Carbon cannot reduce these oxides; electrolysis is used.
Which of these is not a fossil fuel?
1. Biogas
2. Natural gas
3. Petroleum
4. Coal
Answer
A. Biogas
Biogas is made from recent organic waste, not from ancient fossils.
The main component of CNG is
1. butane
2. methane
3. ethane only
4. propane
Answer
B. methane
CNG is mainly methane; LPG is butane and propane.
Which fraction of petroleum rises to the top of the fractionating column?
1. Diesel
2. Bitumen
3. Lubricating oil
4. Petroleum gas
Answer
D. Petroleum gas
The lightest fraction with lowest boiling point rises highest.
Which non-metal is the only one that is a liquid at room temperature?
1. Sulphur
2. Iodine
3. Bromine
4. Phosphorus
Answer
C. Bromine
Bromine is a red-brown liquid; iodine, sulphur and phosphorus are solids.
White phosphorus is stored under water because it
1. reacts with nitrogen
2. dissolves in air
3. is radioactive
4. catches fire in air
Answer
D. catches fire in air
It is very reactive and ignites in air.
What is the percentage of iron in Fe2O3? (Fe = 56, O = 16)
1. 56
2. 60
3. 70
4. 80
Answer
C. 70
Molar mass 160; iron 112; 112/160 = 70 percent.
How many grams of CO2 are produced by complete decomposition of 200 g of CaCO3? (CaCO3 = 100, CO2 = 44)
1. 44 g
2. 88 g
3. 100 g
4. 176 g
Answer
B. 88 g
CaCO3 gives CaO + CO2; 100 g gives 44 g, so 200 g gives 88 g.
What mass of aluminium oxide (Al2O3 = 102) is formed from 27 g of aluminium (Al = 27) in 4Al + 3O2 -> 2Al2O3?
1. 51 g
2. 27 g
3. 204 g
4. 102 g
Answer
A. 51 g
4 x 27 = 108 g Al gives 204 g; 27 g gives 51 g.
The molar mass of ZnO is 81 (Zn = 65, O = 16). What mass of zinc is obtained from 81 g of ZnO by complete reduction with carbon?
1. 65 g
2. 130 g
3. 81 g
4. 16 g
Answer
A. 65 g
One mole of ZnO gives one mole of Zn, which weighs 65 g.
The percentage of oxygen in Al2O3 (Al = 27, O = 16) is closest to
1. 16
2. 47
3. 27
4. 53
Answer
B. 47
Mass of 3 O = 48; molar mass 102; 48/102 is about 47 percent.
How many moles of aluminium are needed to reduce 1 mole of Fe2O3 in the thermite reaction Fe2O3 + 2Al -> 2Fe + Al2O3?
1. 1
2. 3
3. 2
4. 4
Answer
C. 2
The equation shows 2 mol Al per 1 mol Fe2O3.
If 56 g of iron displaces copper completely from copper sulphate solution (Cu = 63.5), the mass of copper formed is
1. 32 g
2. 56 g
3. 127 g
4. 63.5 g
Answer
D. 63.5 g
Fe + CuSO4 gives FeSO4 + Cu; one mole to one mole.
A sample of 22 carat gold contains about how much gold by mass?
1. 91.6 percent
2. 75 percent
3. 50 percent
4. 99.9 percent
Answer
A. 91.6 percent
22/24 = 0.916.
The mass of carbon dioxide formed when 12 g of carbon burns completely in oxygen (C = 12, CO2 = 44) is
1. 32 g
2. 12 g
3. 44 g
4. 22 g
Answer
C. 44 g
C + O2 gives CO2; 1 mole C gives 1 mole CO2 = 44 g.
Calculate the mass percentage of sulphur in SO2 (S = 32, O = 16).
1. 66.7
2. 50
3. 32
4. 25
Answer
B. 50
Molar mass 64; sulphur 32; 32/64 = 50 percent.
Which one is correct about the copper that turns green when exposed to moist air?
1. It forms copper sulphide
2. It forms copper nitrate
3. It forms copper oxide only
4. It forms basic copper carbonate
Answer
D. It forms basic copper carbonate
The green coating on copper is basic copper carbonate.
Which method protects iron by attaching a more reactive metal such as magnesium to it?
1. Sacrificial protection
2. Tin plating
3. Oiling
4. Painting
Answer
A. Sacrificial protection
The more reactive metal corrodes in place of iron.
Match the metal with its alloy partner: Bronze is made of copper and
1. zinc
2. tin
3. nickel
4. lead
Answer
B. tin
Bronze is copper plus tin.
Which of the following is the most abundant metal in the Earth's crust?
1. Calcium
2. Copper
3. Aluminium
4. Iron
Answer
C. Aluminium
Aluminium is the most abundant metal in the crust; oxygen is the most abundant element.
Which of the following is not a physical property typical of non-metals?
1. Dull appearance
2. Poor conduction of heat
3. Brittleness
4. High malleability
Answer
D. High malleability
Malleability is a metal property; non-metal solids are brittle.
Which statement about metals in the reactivity series is correct?
1. Metals above hydrogen displace hydrogen from dilute acids
2. Gold is more reactive than sodium
3. Silver is above iron
4. Copper displaces hydrogen from dilute acids
Answer
A. Metals above hydrogen displace hydrogen from dilute acids
Only metals above hydrogen can release hydrogen from dilute acid.
Consider the statements. 1. Carbonate ores are converted to oxides by calcination. 2. Calcination is done in excess of air. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Calcination is heating in limited air or no air, so only statement 1 is correct.
Consider the statements. 1. Rusting of iron needs both air and water. 2. Rust is formed by the action of dry air alone. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Rusting needs oxygen and moisture; dry air alone does not rust iron.
Consider the statements. 1. Graphite is a good conductor of electricity. 2. Diamond is a good conductor of electricity. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Graphite has free electrons; diamond has none.
Consider the statements. 1. Anthracite has higher carbon content than lignite. 2. Natural gas is mostly methane. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are standard facts about coal and natural gas.
Consider the statements. 1. Alloys are generally harder than pure metals. 2. Stainless steel contains no iron. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Stainless steel is mainly iron with chromium, nickel and carbon.
Consider the statements. 1. Sodium is extracted by reducing its oxide with carbon. 2. Highly reactive metals are extracted by electrolysis. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Sodium is obtained by electrolysis of molten sodium chloride.
Consider the statements. 1. Mercury is liquid at room temperature. 2. All non-metals are poor conductors of electricity. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Graphite is a non-metal that conducts electricity, so statement 2 is false.
Consider the statements. 1. Zinc is more reactive than copper. 2. Copper can displace zinc from zinc sulphate solution. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
A more reactive metal displaces a less reactive one, not the reverse.

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Chapter quiz · 10 questions

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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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