Using materials

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Corrosion and Rusting

Corrosion is the destruction of materials by chemical substances in their environment over time.
Most metals corrode in the presence of oxygen to form the corresponding metal oxide.
Rusting is the specific corrosion of iron in the presence of both water and oxygen from the air.
The word equation for rusting is: iron + water + oxygen → hydrated iron(III) oxide.
Rust is a soft solid that flakes off, exposing fresh iron underneath, so corrosion continues and weakens the structure.
Corrosion is a redox process: the metal loses electrons and is oxidised, while oxygen gains electrons and is reduced.

Investigating Rusting

Both air (oxygen) and water must be present for iron to rust.
A simple experiment uses three test tubes: one with nail in water, one with nail in boiled water covered with oil, and one with nail in dry air (using calcium chloride).
Boiled water removes dissolved oxygen; a layer of oil prevents oxygen from dissolving back in.
Calcium chloride is a drying agent that absorbs water vapour, keeping the air dry.
The nail in ordinary water rusts; the nail in boiled water with oil does not rust; the nail in dry air does not rust.
These results show that both air and water are necessary for rusting.

Preventing Rusting: Barrier Methods

Barrier methods stop rusting by coating the iron to prevent contact with water and oxygen.
Common barrier methods include painting, oiling, greasing, and electroplating.
If the coating is scratched or washed away, the iron is exposed and rusting can start again.
Rust is porous, so once rusting begins, air and water can reach fresh metal underneath a damaged coating, and corrosion continues internally.
Electroplating coats one metal with a layer of a different metal, often to improve corrosion resistance or appearance.
In electroplating, the anode is the pure metal used for coating, the cathode is the object to be plated, and the electrolyte is a solution of a salt of the coating metal.

Sacrificial Protection and Galvanising

Sacrificial protection uses a more reactive metal attached to a less reactive metal; the more reactive metal corrodes first, protecting the other.
Galvanising is coating iron with a layer of zinc, either by dipping in molten zinc or by electroplating.
Zinc forms a protective layer of zinc carbonate (ZnCO₃) with oxygen and carbon dioxide in the air, acting as a barrier.
If the zinc coating is scratched, the iron is still protected because zinc is more reactive than iron and corrodes preferentially.
Zinc loses electrons more readily than iron: Zn → Zn²⁺ + 2e⁻. The electrons are accepted by iron, keeping it reduced and preventing it from oxidising.
The electrons donated by zinc can also react with hydrogen ions in water to produce hydrogen gas: 2H⁺ + 2e⁻ → H₂.
Ships' hulls may have blocks of magnesium or magnesium alloys attached; these corrode instead of the iron hull, providing sacrificial protection.
For continued protection, the sacrificial metal (e.g., zinc bars) must be replaced before it completely corrodes.

Aluminium and its Oxide Layer

Aluminium has a natural oxide coating that protects the metal from further corrosion.
The oxide layer acts as a barrier, preventing contact with water and oxygen.
This is why aluminium is resistant to corrosion despite being a reactive metal.

Alloys: Structure and Properties

An alloy is a mixture of two or more metals, or a metal with a non-metal such as carbon; the components are not chemically combined.
Alloys often have different properties from the pure metals, such as greater strength, hardness, or resistance to corrosion or extreme temperatures.
Alloys are harder than pure metals because the atoms of different sizes distort the regular arrangement of atoms.
This distortion makes it more difficult for the layers of atoms to slide over each other, so the alloy is less malleable.
In particle diagrams, an alloy is shown with uneven sized particles and distorted layers.

Structure of an alloy

Common Alloys and Their Uses

Bronze is an alloy of copper and tin; it is harder than copper and is used for ornaments and medals.
Brass is an alloy of copper and zinc (often about 70% copper, 30% zinc); it is decorative, corrosion resistant, and used for plumbing and carpentry fittings.
Steel is an alloy of iron and carbon. High carbon steel is strong but brittle (used for cutting tools); low carbon steel is softer and more easily shaped (used for building frames, car bodies).
Stainless steel contains iron, chromium, and nickel; it is hard and resistant to corrosion, used for cutlery and cookware.
Magnalium is an alloy of aluminium and magnesium; it is stronger, lighter, and more corrosion resistant than pure aluminium, used in aircraft and car construction.
Magnalium with about 50% magnesium is used in fireworks because it is more stable than pure magnesium but still burns brightly.
Gold alloys are made with silver, copper, and zinc to add strength and toughness; pure gold is 24 carat, and 18 carat gold is 75% gold by mass.
Carats express the purity of gold: 24 carat = 100% gold, 12 carat = 50% gold.

Transition Metals: Properties and Uses

Transition metals are hard, strong, lustrous, and good conductors of heat and electricity.
They have high densities and very high melting points.
Transition metals can form ions with different charges (multiple oxidation states) and their compounds are often coloured.
Transition metals are used as catalysts; for example, iron in the Haber process, vanadium pentoxide in the Contact process, and nickel in hydrogenation of alkenes.
They are used in medicine and surgery, such as titanium for bone and joint replacements due to its biocompatibility.
They are also used in dyes, paints, stained glass, and jewellery.

Ceramics, Polymers, and Composites

Ceramics are non-metal solids with high melting points, used in construction and domestic appliances.
Soda-lime glass is made by heating a mixture of sand, sodium carbonate, and limestone; borosilicate glass is made from sand and boron trioxide and has a higher melting point.
Clay ceramics are made by shaping wet clay and firing it at high temperatures; they are strong and used for bricks.
Polymers have properties that depend on the monomers used and the conditions of polymerisation; ethene can form low density (LD) or high density (HD) poly(ethene).
Thermosoftening polymers have tangled chains with no cross-links, melt when heated, and can be remoulded; used for packaging and bottles.
Thermosetting polymers have strong cross-links between chains, do not melt when heated, and are rigid; used in electrical plugs.
A composite is made of two distinct materials: a reinforcement (fibres or fragments) embedded in a matrix (binder).
Examples of composites include fibreglass (glass fibres in polymer resin), concrete (aggregate in cement), carbon fibre (carbon fibres in polymer resin), and wood (cellulose fibres in organic polymer).

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1.What is the general name for the destruction of materials by chemical reactions with substances in the environment?
Easy
- ACorrosion
- BRusting
- CGalvanising
- DSacrificial protection
2.Which two substances are both needed for iron to rust?
Easy
- AWater and oxygen
- BWater and nitrogen
- COxygen and nitrogen
- DOxygen and carbon dioxide
3.All corrosion is rusting.
Easy
True or false?
4.Which method of preventing rusting works by coating the iron with a more reactive metal?
Easy
- AGalvanising
- BPainting
- CGreasing
- DElectroplating with tin
5.What is an alloy?
Easy
- AA mixture of two or more metals or a metal with a non-metal
- BA chemical compound of two metals
- CA pure metal with no other elements
- DA composite of a metal and a ceramic
6.Alloys are usually harder than the pure metals they contain.
Easy
True or false?
7.Which alloy is a mixture of copper and zinc?
Medium
- ABrass
- BBronze
- CSteel
- DMagnalium
8.Which alloy is used for cutlery because it is hard and resistant to corrosion?
Medium
- AStainless steel
- BHigh carbon steel
- CBronze
- DBrass

Soal lainnya

9.Which type of steel is strong but brittle?
Medium
- AHigh carbon steel
- BLow carbon steel
- CStainless steel
- DCast iron
10.Soda-lime glass is made by heating a mixture of which three substances?
Medium
- ASand, sodium carbonate and limestone
- BSand, boron trioxide and limestone
- CClay, sand and limestone
- DSand, sodium carbonate and boron trioxide
11.Borosilicate glass melts at a higher temperature than soda-lime glass.
Easy
True or false?
12.Which statement about thermosetting polymers is correct?
Medium
- AThey have strong cross-links between chains and do not melt when heated
- BThey have no cross-links and can be remelted and reshaped
- CThey are made only from ethene monomers
- DThey have low melting points and are used for packaging
13.Which polymer is made at high pressure and moderate temperature and is used for bags and bottles where flexibility is needed?
Medium
- ALow density poly(ethene)
- BHigh density poly(ethene)
- CThermosetting polymer
- DBorosilicate polymer
14.Thermosoftening polymers consist of individual tangled chains with no cross-links between them.
Medium
True or false?
15.In a composite, what is the matrix?
Medium
- AThe material that surrounds and binds the reinforcement together
- BThe fibres or fragments that are embedded in the material
- CThe chemical bond between two metals
- DThe polymer that melts when heated
16.Which of the following is an example of a composite?
Medium
- AFibreglass
- BBrass
- CBronze
- DSoda-lime glass
17.Alloys are uniform mixtures of metals, whereas composites have two or more distinguishable materials.
Medium
True or false?
18.Why is aluminium used for aircraft bodies?
Medium
- AIt has a low density and its oxide coating resists corrosion
- BIt is a pure metal with a high density
- CIt is more reactive than iron and corrodes easily
- DIt is a composite material that is very strong
19.Which property makes clay ceramics suitable for making bricks?
Medium
- AThey are very strong and can withstand high pressures and weights
- BThey are flexible and can be melted and remoulded
- CThey are low density and good electrical conductors
- DThey are transparent and insulate against heat
20.Which of the following are barrier methods for preventing rusting? (select all that apply)
Medium
- APainting
- BGreasing
- CCoating with plastic
- DGalvanising
- EAttaching a zinc block
21.Which of the following are properties of transition metals? (select all that apply)
Medium
- AThey are good conductors of heat and electricity
- BThey have high melting points
- CThey form coloured compounds
- DThey are soft and have low densities
- EThey form colourless compounds
22.Match each alloy to its composition.
Medium
- Brass
- Bronze
- Stainless steel
- Magnalium
- Copper and zinc
- Copper and tin
- Iron, chromium and nickel
- Aluminium and magnesium
23.Arrange the steps in the correct order to describe how galvanising protects iron from rusting.
Medium
- Iron is coated with a layer of zinc
- Zinc reacts with oxygen and carbon dioxide to form zinc carbonate
- The zinc carbonate layer acts as a barrier
- If the coating is scratched, zinc corrodes preferentially
- The iron remains protected by sacrificial protection
24.What is the brown deposit?
Easy
- AHydrated iron(III) oxide
- BIron oxide only
- CZinc carbonate
- DHydrated copper(II) oxide
25.The nail would still rust if the water was boiled and covered with a layer of oil.
Easy
True or false?
26.Arrange the steps to show how zinc protects iron by sacrificial protection when the zinc coating is scratched.
Medium
- Zinc loses electrons and is oxidised to Zn²⁺ ions
- The electrons are transferred to the iron
- Iron remains in the reduced state and does not form iron(III) ions
- The iron does not rust
27.Which of the following statements about galvanising are correct? (select all that apply)
Medium
- AGalvanising coats iron with a layer of zinc.
- BThe zinc layer acts as a barrier to water and oxygen.
- CIf the zinc layer is scratched, the iron rusts immediately.
- DZinc is more reactive than iron, so it corrodes preferentially.
- EGalvanising works only by sacrificial protection, not as a barrier.
28.Sacrificial protection works because the more reactive metal corrodes instead of the less reactive metal.
Easy
True or false?
29.Which property of aluminium makes it suitable for aircraft bodies?
Medium
- AIt has a low density.
- BIt is a good conductor of electricity.
- CIt has a high melting point.
- DIt is magnetic.
30.Which statement correctly describes the structure of a thermosetting polymer?
Medium
- AIt consists of individual tangled chains with no cross-links.
- BIt has strong cross-links between polymer chains.
- CIt is made of small molecules that slide over each other.
- DIt melts easily when heated.
31.Which of the following are examples of composites? (select all that apply)
Medium
- AFibreglass
- BConcrete
- CCarbon fibre
- DBrass
- EWood
32.A manufacturer wants to make a batch of gold jewellery that is 18 carat. The gold used is alloyed with silver, copper and zinc. Which of the following statements about this alloy are correct? (select all that apply)
Medium
- AThe alloy contains 75% gold by mass.
- BThe alloy contains 18% gold by mass.
- CThe alloy is a mixture, not a compound.
- DThe alloy is 24 carat gold with 18 parts of other metals added.
- EThe alloy is pure gold.
33.A sample of solder is made by mixing 22.5 g of lead with 15.0 g of tin. What is the percentage by mass of tin in the solder?
Hard
- A40.0%
- B60.0%
- C66.7%
- D15.0%
34.A bicycle chain is made of steel and is lubricated with oil. How does this prevent corrosion of the chain?
Medium
- AThe oil acts as a barrier, preventing water and oxygen from reaching the steel surface.
- BThe oil reacts with the steel to form a protective oxide layer.
- CThe oil is more reactive than iron and corrodes instead of the steel.
- DThe oil lowers the temperature of the steel so it cannot rust.
35.An iron bucket is coated in zinc. Over many years the zinc coating is scratched, exposing some iron, and the bucket is left outside in the rain. The exposed iron does not rust. Which statement explains this?
Medium
- AZinc is more reactive than iron, so it corrodes preferentially and protects the iron by sacrificial protection.
- BZinc is less reactive than iron, so it acts only as a physical barrier.
- CZinc reacts with iron to form an alloy that does not rust.
- DZinc prevents water from reaching the iron by absorbing it.
36.Match each material to its correct description.
Medium
- Soda-lime glass
- Borosilicate glass
- Clay ceramic
- Thermosetting polymer
- Thermosoftening polymer
- Made by heating sand, sodium carbonate and limestone
- Made from sand and boron trioxide; melts at a higher temperature
- Made by shaping wet clay and firing it in a furnace
- Has strong cross-links between chains and does not melt when heated
- Has tangled chains with no cross-links and can be remelted and reshaped
37.A student sets up three test tubes to investigate rusting. Tube 1: nail in tap water. Tube 2: nail in boiled water covered with a layer of oil. Tube 3: nail in dry air with calcium chloride. Which tube(s) will show rust after one week?
Medium
- ATube 1 only
- BTubes 1 and 2 only
- CTubes 2 and 3 only
- DAll three tubes
38.In an experiment to show that both air and water are needed for iron to rust, why is the water in one test tube boiled before the nail is added?
Easy
- ATo remove dissolved oxygen from the water
- BTo sterilise the water so bacteria cannot grow
- CTo increase the rate of rusting
- DTo remove any dissolved salts from the water
39.Which of the following are reasons why electroplating is carried out on metal objects? (select all that apply)
Medium
- ATo improve the appearance of the metal
- BTo make the metal more resistant to corrosion
- CTo make the metal softer and more malleable
- DTo increase the density of the metal
- ETo make the metal a better electrical conductor
40.A student investigates rusting by wrapping magnesium ribbon around an iron rod and placing it in a boiling tube with water. A second identical iron rod with no magnesium is placed in another boiling tube with water. After a few days, the first rod is unchanged but the magnesium has started to disappear, while the second rod has a brown deposit. Which statement best explains these results?
Medium
- AMagnesium is more reactive than iron, so it corrodes instead of the iron (sacrificial protection).
- BMagnesium is less reactive than iron, so it acts as a barrier preventing water from reaching the iron.
- CMagnesium dissolves in water to form an acid that stops rusting.
- DMagnesium reacts with the brown deposit to remove it from the iron.
41.Complete the sentence about rusting.
Easy
Rusting is the corrosion of iron in the presence of water and ____ from the air.
42.A sample of magnalium contains 3.15 g of magnesium in a total mass of 63.0 g. Calculate the percentage by mass of magnesium in the magnalium.
Medium
43.A sample of solder contains 15.0 g of tin in a total mass of 37.5 g. Calculate the percentage of tin in the solder.
Medium
44.A small iron bucket has a surface area of 0.68 m². Calculate the mass of zinc required to coat the surface with a layer of zinc of 200 g m⁻².
Medium
45.18 carat gold contains 75% gold. Calculate the mass of gold in 2 kg of 18 carat gold.
Medium
46.Complete the sentence about galvanising.
Medium
Galvanising involves coating iron with a layer of ____.
47.Complete the sentence about alloys.
Medium
An alloy is a ____ of two or more metals or a metal with a non-metal.
48.What is the name of the alloy made from copper and tin?
Medium
49.What is the name of the process where iron is coated with a layer of zinc to prevent rusting?
Medium
50.Name the other substance, besides water, that is needed for the nail to rust.
Medium
51.Complete the sentence about the conditions needed for iron to rust.
Easy
Iron rusts when it is in contact with both ____ and ____.
52.A sample of brass contains 70% copper and 30% zinc. Calculate the mass of copper in 250 g of this brass.
Medium
53.Explain why alloys are harder than pure metals.
Medium
54.Explain how sacrificial protection prevents iron from rusting, using zinc as an example.
Hard
55.Compare the structure and behaviour of thermosoftening and thermosetting polymers when heated.
Hard
56.Describe how you would investigate the conditions needed for iron to rust.
Medium
57.Explain, in terms of structure and bonding, why metals have high melting points.
Medium
58.A sample of magnalium contains 3.15 g of magnesium in a total mass of 63.0 g. Calculate the percentage by mass of magnesium in the magnalium.
Medium
- A5 %
- B6 %
- C7 %
- D4 %
59.A sample of solder contains 15.0 g of tin in a total mass of 37.5 g. Calculate the percentage of tin in the solder.
Medium
- A40 %
- B44 %
- C48 %
- D36 %
60.A small iron bucket has a surface area of 0.68 m². Calculate the mass of zinc required to coat the surface with a layer of zinc of 200 g m⁻².
Medium
- A136 g
- B150 g
- C164 g
- D122 g
61.18 carat gold contains 75% gold. Calculate the mass of gold in 2 kg of 18 carat gold.
Medium
- A2.5 kg
- B0.5 kg
- C1.5 kg
- D3.5 kg
62.A sample of brass contains 70% copper and 30% zinc. Calculate the mass of copper in 250 g of this brass.
Medium
- A157 g
- B193 g
- C211 g
- D175 g

Kartu flash

What is corrosion?

The destruction of materials by chemical substances in their environment acting on them over time. Most metals corrode in the presence of oxygen to form the corresponding metal oxide.

What is rusting?

The specific corrosion of iron in the presence of water and oxygen from the air, forming hydrated iron(III) oxide.

Give the word equation for the rusting of iron.

iron + water + oxygen → hydrated iron(III) oxide

Which two substances are needed for iron to rust?

Both water and oxygen (from the air) must be present.

Why does rusting eventually weaken iron structures?

Rust is a soft, porous solid that flakes off easily, exposing fresh iron underneath, so the iron corrodes internally until all of it has rusted.

In the rusting experiment, why is boiled water used in one test tube?

Boiling removes dissolved oxygen from the water, so the nail has water but no oxygen and does not rust.

In the rusting experiment, why is a layer of oil placed on top of the boiled water?

The oil acts as a barrier, preventing oxygen from the air diffusing back into the water.

In the rusting experiment, what is the role of calcium chloride?

It is a drying agent that absorbs water molecules, so the nail has air but no water and does not rust.

What do the results of the rusting experiment show?

Only the nail in contact with both air and water rusts, showing that both oxygen and water are needed for rusting.

What is a barrier method of preventing rusting?

Coating iron so that water and oxygen cannot reach it, for example with paint, oil, grease, plastic or electroplating.

Why does a barrier method fail once the coating is scratched?

The iron is exposed to water and oxygen again and will rust, and because rust is porous it continues to corrode underneath the broken coating.

What is galvanising?

Coating iron with a layer of zinc, either by electroplating or by dipping the iron into molten zinc.

How does galvanising protect iron if the zinc layer is scratched?

Zinc is more reactive than iron, so it corrodes preferentially by sacrificial protection, losing its electrons instead of the iron.

Explain sacrificial protection in terms of the reactivity series.

A more reactive metal is attached to or coated on the less reactive metal; the more reactive metal is oxidised and corrodes first, protecting the other metal.

Why do zinc bars on a ship's hull need to be replaced?

They corrode instead of the iron, so they must be replaced before they completely corrode to keep protecting the hull.

How does aluminium resist corrosion?

Aluminium has an oxide coating that acts as a barrier, protecting the metal from further corrosion.

What is an alloy?

A mixture of two or more metals, or a metal mixed with a non-metal such as carbon, mixed physically but not chemically combined.

Why are alloys harder than pure metals?

The atoms in an alloy are different sizes, which distorts the regular arrangement and makes it harder for the layers of atoms to slide over each other.

What is bronze made of and what is it used for?

Bronze is an alloy of copper and tin; it is harder than copper and is used for ornaments and medals.

What is brass made of and what is it used for?

Brass is an alloy of copper and zinc; it is decorative and corrosion resistant and is used for plumbing and carpentry fittings.

What is stainless steel made of and why is it used for cutlery?

Stainless steel is iron alloyed with chromium and nickel; it is hard and resistant to corrosion.

How do high carbon steel and low carbon steel differ?

High carbon steel is strong but brittle, while low carbon steel is softer and more easily shaped.

Why are aluminium alloys used for aircraft bodies?

They are stronger, lighter and more corrosion resistant than pure aluminium.

What is magnalium and what is it used for?

An alloy of aluminium and magnesium; it is used in aircraft and automobile construction and, with 50% magnesium, in fireworks because it is more stable than pure magnesium but still burns brightly.

What do carats measure in gold jewellery?

The purity of the gold: 24 carat is pure gold (100%) and 18 carat is 75% gold.

Why is gold alloyed with metals such as copper, zinc and silver for jewellery?

Pure gold is soft and malleable, so other metals are added to give it strength and toughness.

What is electroplating?

Coating the surface of one metal with a layer of a different, less reactive metal using an electrolyte and an electric current.

Give two reasons for electroplating a metal object.

To make it more resistant to corrosion or damage, and to improve its appearance.

What are ceramics?

Non-metal solids with high melting points, widely used in construction materials and domestic appliances.

How is soda-lime glass made?

By heating a mixture of limestone, sand and sodium carbonate until it melts; it solidifies on cooling.

How does borosilicate glass differ from soda-lime glass?

It is made from sand and boron trioxide and has a higher melting point than soda-lime glass.

How are clay ceramics made?

Wet clay is shaped and then fired at high temperature in a furnace, hardening it into a strong ceramic such as bricks.

What two things determine the properties of a polymer?

The monomers it is made from and the conditions under which it is made.

How is low density poly(ethene) made and what is it used for?

It is made at high pressure and moderate temperature; it is flexible and used for bags and bottles.

How is high density poly(ethene) made and what is it used for?

It is made at lower temperatures and pressures with a catalyst; it is rigid and used for water tanks, mouldings and drain pipes.

What is the difference in structure between thermosoftening and thermosetting polymers?

Thermosoftening polymers have individual tangled chains with no cross-links; thermosetting polymers have strong cross-links between their chains.

Why do thermosetting polymers not melt when heated?

They have strong cross-links between the chains, so a lot of energy would be needed to overcome them.

Why can thermosoftening polymers be melted and remoulded?

Their chains have no cross-links between them, so they have low melting points and can be reshaped.

What is a composite?

A material made of two distinct components: a reinforcement of fibres or fragments embedded in a matrix that surrounds and binds them together.

Give two examples of composites and their components.

Fibreglass (glass fibres in polymer resin) and steel reinforced concrete (aggregate in cement); wood is a natural composite.

Why are carbon fibres used in aviation and racing bicycles?

They are extremely strong and low in weight.

What is the difference between an alloy and a composite?

Alloys are uniform mixtures of metals, whereas composites contain two or more distinguishable materials.

Give two typical properties of transition metals.

They have high melting points and high densities, and they form coloured compounds.

Why can transition metals act as catalysts?

They can interchange between a range of oxidation states, allowing them to form complexes with reagents and donate or accept electrons.

Give two uses of transition metals in medicine and industry.

Titanium is used for limb and joint replacements because it bonds with bone, and transition metals form coloured compounds used in dyes, paints and stained glass.

Why is iron not suitable for the electrodes of a hydrogen-oxygen fuel cell?

Iron corrodes (rusts) in the presence of water and oxygen, so it would not last.

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