C10 Metals

Question 1

What are the physical properties of metals?

Answer 1

Physical properties of metals:
-Solids.
-Malleable (can be hammered and made into different shapes).
-Good conductors of heat and electricity.
-Tend to be lustrous.
-High density.
-High melting points.

Question 2

What ions do metals form? (charge)

Answer 2

Metals lose electrons and therefore form positive ions.

Question 3

What is metallic bonding?

Answer 3

Metal atoms are held together in a giant metallic lattice structure. Within the structure, atoms lose electrons to becoming positively charged ions. The electrons become free/delocalised and move between the positive ions like a ‘sea of electrons’.

Question 4

Why can metals conduct electricity?

Answer 4

Metals can conduct electricity because there are delocalised electrons travelling through the structure - between the positive ions.

Question 5

Why are metals malleable?

Answer 5

Metals are malleable because they consist of layers of atoms that can slide over each other when the metal is bent/hammered. The metallic bonding is not disrupted when hammered because the electrons do not belong to any particular atom and just move freely. When hammered, the metallic bonds are not broken and instead flexible.

Question 6

What is an alloy?

Answer 6

An alloy is a mixture of two or more metals or a metal with a non-metal.
-At least one of the elements must be a metal.

Question 7

What are examples of alloys?

Answer 7

Steel which contains iron and carbon.
Brass which contains copper and zinc.

Question 8

How do alloys’ properties differ to the metal they contain?

Answer 8

Alloys often have properties that are very different from the metal they contain. They are:
-Harder and stronger.
-More resistant to corrosion.

Question 9

Why are alloys used instead of pure metals?

Answer 9

Alloys contain different sizes of atoms which distorts the normally regularly arrangements of atoms in metals. This makes it more difficult for the layers to slide over each other, so alloys are much harder than the pure metal.

Question 10

Which alloy is resistant to corrosion?

Answer 10

Stainless steel is an alloy of chromium and nickel. It is resistant to corrosion.

Question 11

How much carbon does mild steel contain?

Answer 11

Mild steel contains about about 0.25% carbon which allows it to be easily shaped.

Question 12

How much carbon does medium steel contain?

Answer 12

Medium steel contains about 0.30-0.60% carbon.

Question 13

How much carbon does high carbon steel contain?

Answer 13

High carbon steel contains about 2.5% carbon which makes it very hard (in comparison to low carbon steel).

Question 14

Why are alloys harder than pure iron?

Answer 14

Alloys are harder than pure iron because of the different sized metal ions that disrupt the regular arrangement of layers of ions, preventing them from sliding over each other as easily. The more different sized metal ions, the harder the alloy will be.

Question 15

How can aluminium be used for aeroplane bodies?

Answer 15

Aluminium is used in aircraft parts because of its high strength-to-weight ratio and very low density.

Question 16

How can aluminium be used for food cans?

Answer 16

Aluminium can be used for food cans as it is non-toxic and resistant to corrosion and acidic food stuffs.

Question 17

Explain aluminium’s apparent lack of reactivity.

Answer 17

Aluminium is placed high on the reactivity series despite it not reacting with water of acids. This is because the surface of aluminium metal reacts with oxygen in the air which forms a protecting coating of aluminium oxide.

4Al (s) + 3O2 (g) → 2Al2O3 (s)

Question 18

Describe the protective layer of aluminium oxide of aluminium metal.

Answer 18

the aluminium oxide is tough, unreactive and resistant to corrosion. It adheres very strongly to the aluminium surface and protects it from reactions with other substances, hence making it appear unreactive.

Question 19

What are the uses of mild steel? And why?

Answer 19

Mild steel is used for car bodies and machinery because it is tough, ductile, malleable and has good tensile strength.

Question 20

What are the uses of stainless steel? And why?

Answer 20

Stainless steel is used for chemical plants and cutlery because it is resistant to corrosion.

Question 21

What is galvanising?

Answer 21

Galvanising is to coat (iron or steel) with a protective layer of zinc.

Question 22

What is zinc used for?

Answer 22

Zinc is used to galvanise iron or mild steel to prevent rusting. The zinc forms a coating on the surface of the iron or steel. The zinc prevents corrosive substances from reaching the underlying iron or steel.

Question 23

Why is zinc used to make brass?

Answer 23

Brass is an alloy of zinc and copper. Zinc is used to make brass because it is what gives brass its good strength and resistance to corrosion.