Alloys as useful materials

This question is about the transition metals iron and copper.

When iron rods are left out in the rain for a few weeks, the rods corrode and become covered in a brown solid.

State the name of this brown solid.

Place ticks () in boxes to show which two substances in the air react with iron to form the brown solid.

State one way to prevent the corrosion of iron rods that will be used outside.

In an experiment, 5 iron rods were left outside in the rain for a few weeks.

The mass of the iron rods was found before they were left outside and again after a few weeks.

Figure 12 shows the recorded masses.

Use this information to calculate the mean increase in mass of one iron rod.

mean increase in mass of one iron rod =_........ g

Figure 13 shows the atoms in pure gold and in a gold alloy.

State the meaning of the term alloy.

*(ii) Using Figure 13, compare pure gold and the gold alloy by

• describing how their atoms are arranged

• explaining the differences between the strength of the pure gold and the gold alloy.

Copper, iron, nickel and zinc are all metallic elements.

Which row of the table applies to copper?

Many ships are made of steel. Steel is an alloy that contains iron. Figure 4 shows blocks of zinc attached to a steel ship.

Explain how iron is protected from rusting by the zinc blocks.

Alloys of copper and nickel are used for some coins.

Figure 5 shows the relative strengths of copper and nickel and some of their alloys.

On Figure 6

• add suitable scales to the vertical and horizontal axes

• plot a graph of relative strength against percentage of nickel

• draw a curve of best fit.

A coin is made from an alloy that contains 70% copper and 30% nickel.

Determine the relative strength of this coin from your graph on Figure 6.

relative strength of the coin =_........

Explain, using Figure 6, how the percentage of nickel affects the relative strength of the alloys of copper and nickel.

Chemical cells produce a voltage.

A chemical cell can be made by placing the metals copper and iron in a beaker of sodium chloride solution as shown in Figure 1.

Describe what will happen to the reading on the voltmeter over a long period of time.

Iron is a transition metal.

Which of the following is most likely to be a property of iron?

An iron atom has a diameter of 2.5210^–10 m.

What is the size of this iron atom in nanometres?

Figure 2 shows the arrangement of atoms in three different alloys of copper and

Explain which of the three alloys, A, B and C, is the strongest.

Most of the gold used in jewellery is not pure gold but alloys of gold.

The purity of gold is measured in carats.

Figure 3 shows how the percentage of gold is related to the purity of gold measured in carats.

State the relationship between the percentage of gold and the number of carats.

Figure 4 shows the arrangement of atoms in pure gold and in an alloy of gold.

Using Figure 4, explain why alloys of gold are stronger than pure gold.

Explain one property of alloys of gold, other than their strength, that makes them suitable for use in jewellery.

Steel is an alloy containing iron.

When exposed to damp air, some steels will corrode to form rust.

Which gas in the air is needed for corrosion to occur?

What type of reaction happens when the iron in steel corrodes?

Rust can be removed from steel by treating it with dilute hydrochloric acid.

One product formed in this reaction is iron chloride, FeCl₃.

Calculate the relative formula mass of this iron chloride.

(relative atomic masses: Fe = 56.0, C l = 35.5)

Figure 6 shows the composition of one type of steel that has a low resistance to corrosion and another type of steel that has a high resistance to corrosion.

Using Figure 6, state which non‑metal is in both types of steel.

Using Figure 6, state which metal is added to steel to increase its resistance to corrosion.

Explain one other way that corrosion of steel can be prevented.

A student is given two nails of the same size but made of different types of steel.

They are also given two boiling tubes and some distilled water.

Devise an experiment to show which nail corrodes more quickly.

Buildings sometimes have water sprinklers to put out fires.

The pipes in some water sprinklers are filled with nitrogen gas to prevent corrosion when the system is not in use.

State what is meant by the term corrosion.

Nitrogen can be made from sodium azide, NaN₃.

Calculate the maximum volume, in cm³, of nitrogen produced from 110 g of sodium azide.

(relative formula mass: NaN₃ = 65;

1 mol of gas occupies 24 dm³ in the conditions used)

*(b) Compare and contrast the properties and uses of pure aluminium and pure copper with the alloys of aluminium and the alloys of copper.

Include in your answer an explanation of the similarities and the differences in the properties and the uses of a pure metal and its alloy.

When iron wool reacts with oxygen from the air, the iron corrodes and iron oxide is formed.

What happens to the iron in this reaction?

A piece of damp iron wool was placed in a measuring cylinder with 50 cm³ of air, as shown in Figure 12.

Figure 13 shows the apparatus one week later.

Complete the table of results.

Use these results to calculate the percentage decrease in the volume of gas in the measuring cylinder after one week.

Not all of the oxygen in the air in the measuring cylinder has reacted with the iron.

Give a reason why.

*(c) Pure metals can be made more useful by converting them into alloys or by electroplating them.

Explain what alloying and electroplating are and how they can make metals more useful.

Chemical cells produce a voltage.

A chemical cell can be made by placing the metals copper and zinc in a beaker of sodium chloride solution.

Figure 1 shows a diagram of this chemical cell.

Describe what will happen to the brightness of the light bulb over a long period of time.

Copper is a transition metal.

Which of the following is most likely to be a property of copper?

A copper atom has a diameter of 0.256 nm.

What is the size of this copper atom in metres?

Brass is an alloy of copper and zinc. One type of brass contains 70% copper.

Zinc atoms are slightly larger than copper atoms.

Draw a labelled diagram in the box to show the arrangement of copper and zinc atoms in this alloy.

Use the circle in the box as a guide to the size of a copper atom.

Aluminium alloys are used instead of pure aluminium in aircraft manufacture.

Explain, in terms of the arrangement of metal particles, why aluminium alloys are stronger than pure aluminium.

A 695.0 g sample of an aluminium-magnesium alloy contains 2.00 % by mass of magnesium.

Calculate the mass of aluminium in this sample.

mass of aluminium =_........

Figure 12 shows a graph of the relative strength of aluminium-magnesium alloys when the percentage by mass of magnesium in the alloy is changed.

percentage by mass of magnesium in alloy

Figure 12

Describe what Figure 12 shows about the relative strength of these alloys when the percentage by mass of magnesium changes.

Determine, using Figure 12, the percentage by mass of aluminium in an aluminium‑magnesium alloy with a relative strength of 103.

percentage by mass of aluminium =_........

Metal objects can be electroplated with gold.

Give two reasons why metal objects are electroplated with gold.

Aluminium alloys are used instead of pure aluminium in aircraft manufacture.

Explain, in terms of the arrangement of metal particles, why aluminium alloys are stronger than pure aluminium.

A 695.0 g sample of an aluminium-magnesium alloy contains 2.00% by mass of magnesium.

Calculate the mass of aluminium in this sample.

mass of aluminium =_........

Figure 5 shows a graph of the relative strength of aluminium-magnesium alloys when the percentage by mass of magnesium in the alloy is changed.

percentage by mass of magnesium in alloy

Figure 5

Describe what Figure 5 shows about the relative strength of these alloys when the percentage by mass of magnesium changes.

Determine, using Figure 5, the percentage by mass of aluminium in an aluminium‑magnesium alloy with a relative strength of 103.

percentage by mass of aluminium =_........

Metal objects can be electroplated with gold.

Give two reasons why metal objects are electroplated with gold.

Transition metals have many uses.

The pie chart in Figure 6 shows the uses of one transition metal.

Calculate the percentage of this transition metal used in construction.

percentage of this transition metal used in construction =_........

Figure 7 shows five statements about iron.

Put ticks () in the boxes in Figure 7 to show which statements are true and which statements are false. The first one has been done for you.

Most iron produced is converted into alloys of iron.

State why alloys have more uses than pure metals.

An alloy of iron contains 0.40 % of molybdenum.

Calculate the mass of molybdenum contained in a 30 g sample of this alloy of iron.

mass of molybdenum =_........

Many transition metals are used to make the reactants in chemical cells.

Figure 8 shows a graph of the voltage produced by a chemical cell as it is used in a torch for many hours.

Suggest an explanation for the shape of the graph.

Alloys of gold are often used to make jewellery. The purity of gold is measured in carats. Different alloys of gold have different carats.

Figure 1 shows the percentage of different metals in two samples of gold.

Explain why 18 carat gold is stronger than 24 carat gold.

You may use diagrams to help your answer.

Figure 2 shows the relationship between the purity of gold in carats and the percentage of gold in the alloy.

A necklace with a mass of 5.0 g was found to contain 2.9 g of gold.

Determine the purity of the gold necklace in carats. Show your working.

purity of the gold necklace =_........ carats

A gold ring contains 3.94 g of gold.

Calculate the number of gold atoms in the ring. (relative atomic mass: Au = 197, Avogadro constant = 6.02 × 10²³)

Show your working.

7 *(a) Pure metals are often converted into more useful alloys. For example, aluminium is converted into an alloy used in aircraft, iron is converted into an alloy used in cutlery and gold alloys are used in jewellery. These processes of alloying change the structures of the metals.

Some properties of pure aluminium, iron and gold are shown in Figure 12.

Explain how alloying changes these pure metals to make the alloys more suitable for the given uses.

Iron objects can corrode when exposed to the atmosphere.

Corrosion involves the oxidation of iron.

State what is meant by oxidation.

Painting iron objects prevents corrosion.

Explain why painting iron objects prevents corrosion.

Corrosion of iron objects can be prevented by painting them or by electroplating them.

State one other way of preventing the corrosion of iron objects.

The apparatus shown in Figure 13 was used to electroplate a spoon with nickel.

State to what the anode and cathode have to be connected in order to carry out the electroplating.

Predict the name of a substance that could be dissolved in water to form the electrolyte for this electroplating.