Chapter 9 - Metals

Question 1

What are some properties of metals?

Answer 1

Metals conduct heat and electricity because they have delocalised electrons that are able to move through the metal structure. They are malleable meaning they can be hammered and mate into different shapes and ductile meaning they can be drawn into wires. This is because the layers of positive metal ions, in the metal structure, are able to slide over each other. They usually have high melting and high boiling points because there is a strong electrostatic attraction between the positive metal ions and delocalised electrons. This strong bond requires a lot of energy to break.

Question 2

What are some properties of non-metals?

Answer 2

Non-metals do not conduct heat and electricity because all of the electrons are involved in covalent bonding. An exception to this is graphite. They are brittle when solid and easily break up, they are not malleable or ductile. An exception to this is graphite. They have low melting and low boiling points because they have weak intermolecular forces that do not require a lot of energy to break. Exceptions to this include diamond and silicon(IV) dioxide

Question 3

What is the reaction of metals with cold water?

Answer 3

Some metals react with cold water. Metals that react with cold water form a metal hydroxide and hydrogen. Metal + cold water → metal hydroxide + hydrogen.

Question 4

What is the reaction of metals with steam?

Answer 4

Some metals react with steam. Metals that react with steam form a metal oxide and hydrogen gas. Metal + steam -> metal oxide + hydrogen.

Question 5

What is the reaction of metals with acids?

Answer 5

Most metals react with acid. When metals react with acids, they form a metal salt and hydrogen. Metal + acid → metal salt + hydrogen.

Question 6

What is the reaction of metals with oxygen?

Answer 6

Unreactive metals such as gold and platinum do not react with oxygen. Some reactive metals such as alkali metals react easily with oxygen. Copper and iron can also react with oxygen although much more slowly. When metals react with oxygen, they form a metal oxide. Metal + oxygen → metal oxide.

Question 7

Why does aluminium appear unreactive?

Answer 7

Aluminium sits above hydrogen in the reactivity series, which means that it is a reactive metal. Aluminium quickly reacts with oxygen to form a protective layer of aluminium oxide, which is why aluminium appears to be unreactive.

Question 8

What are some uses of aluminium?

Answer 8

Aluminium can be used in aeroplane bodies as it has a high strength to weight ration and low density, overhead power cables as it is a good electrical conductor and has a low density, saucepans because it is a good thermal conductor and food cans because it is non-toxic and resistant to corrosion and acidic food stuffs.

Question 9

Why is copper unreactive?

Answer 9

Copper sits below hydrogen in the reactivity series, which means that it is an unreactive metal.

Question 10

What are some uses of copper?

Answer 10

Copper can be used in electrical wiring because it is a very good conductor of electricity and ductile, pots and pans because it is a very good conductor of heat, unreactive and malleable, water pipe because it is non-toxic, unreactive and malleable and surfaces in hospitals as it has antibacterial properties.

Question 11

What is an alloy?

Answer 11

An alloy is a mixture of a metal with other elements. Most alloys contain more than one metal. Some alloys contain non-metals.

Question 12

What is brass and some of its uses?

Answer 12

Brass is an alloy of copper and zinc and is much stronger than either metal. It is used in musical instruments, ornaments and doorknobs.

Question 13

What is stainless steal and some of its uses?

Answer 13

Stainless steel is an alloy of iron and other elements such as chromium, nickel and carbon. It is used in cutlery because of its hardness and resistance to corrosion and rusting.

Question 14

Why are alloys usually harder and stronger than pure metals?

Answer 14

Alloys typically contain atoms of different sizes. This distorts the normally regular arrangement of atoms in metals. This distortion makes it more difficult for the layers to slide over each other. So, alloys are usually harder and stronger than the pure metals.

Question 15

What is the order of the reactivity series?

Answer 15

The order of the reactivity series from most reactive to least reactive is potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead, hydrogen, copper, silver, gold. An easy way to remember this is with the sentence: Please stop calling me a careless zebra instead try learning how copper saves gold.

Question 16

How does potassium, sodium and calcium react with cold water?

Answer 16

Potassium reacts violently with cold water, sodium reacts quickly with cold water and calcium reacts less strongly with cold water. They form a metal hydroxide and hydrogen gas.

Question 17

How does magnesium react with steam?

Answer 17

Magnesium reacts slowly with steam. It forms a metal oxide and hydrogen gas.

Question 18

How does magnesium, zinc and iron react with dilute acids?

Answer 18

Magnesium, zinc and iron will react with dilute acid less strongly than more reactive elements. They form a metal salt and hydrogen gas.

Question 19

Do gold, silver and copper react with acids?

Answer 19

No

Question 20

What metals react with oxygen?

Answer 20

All metals except for gold react with oxygen, forming a metal oxide.

Question 21

When are reactions the most vigorous?

Answer 21

The more vigorous a reaction of a metal, the higher up the reactivity series it is. The greater temperature change in a reaction involving a metal, the more reactive the metal is.

Question 22

How does the tendency to lose ions correlate to reactivity?

Answer 22

Metal atoms for positive ions by the loss of electrons when they react with other substances. The tendency of a metal to lose electrons is a measure of how reactive the metal is. A metal that is high up on the reactivity series loses electrons easily and thus is more reactive.

Question 23

How do displacement reactions occur?

Answer 23

Any metal will displace another metal that is below it in the reactivity series from a solution of one of its salts. This is because more reactive metals lose electrons in form ions more readily than less reactive metals making them better reducing agents. The less reactive metal is a better electron acceptor than the more reactive metal thus the less reactive metal is reduced.

Question 24

Describe magnesium + copper sulphate → magnesium sulfate + copper as an example of a displacement reaction

Answer 24

Magnesium is a reactive metal that can displace copper from copper sulphate solution. Magnesium loses its electrons more easily and the iron of the less reactive metal copper will gain these electrons to form elemental copper. This is easily seen as the more reactive metal slowly disappears from the solution displacing the less reactive metal. Magnesium + copper sulphate → magnesium sulfate + copper.

Question 25

Why does aluminium behave as an unreactive metal?

Answer 25

Aluminium is high in the reactivity series but in reality it does not react with water and their reaction with dilutes acids can be quite slow. This is because it reacts readily with oxygen forming a protective layer of aluminium oxide which is very thin. This layer prevents reaction with water and dilute acid so aluminium can behave as if it is unreactive.

Question 26

What is rust?

Answer 26

Rust is a chemical reaction between iron, water and oxygen to form the compound hydrated iron(III) oxide (rust). Oxygen and water must be present for rusting to occur. During rusting, iron is oxidized. Iron + water +oxygen → hydrated iron(III) oxide

Question 27

How can you prevent rust?

Answer 27

Rust can be prevented by coating iron with barriers that prevent the iron from coming into contact with oxygen and water.

Question 28

How can you prevent rust by using a metal that is more reactive than it?

Answer 28

Iron can be prevented from rusting by using a metal that is more reactive than it. For example, zinc is more reactive than iron therefore it will lose its electrons more easily that iron and is oxidised more easily. Zinc is sacrificed to protect the steel.

Question 29

What is galvanising?

Answer 29

Galvanising is a process where the iron to be protected is coated with a layer of zinc. This can be done by electroplating or dipping it into molten zinc. If the coating is damaged or scratched, the iron is still protected from rusting by sacrificial protection.

Question 30

How do you extract metals depending on their reactivity?

Answer 30

Metals placed higher up on the series (above carbon) have to be extracted using electrolysis. Metals lowed down on the series can be extracted by heating with carbon.

Question 31

How is aluminium extracted?

Answer 31

The main ore of aluminium is bauxite which contains aluminium oxide and is extracted by electrolysis.

Question 32

What is the process of extracting aluminium from bauxite by electrolysis?

Answer 32

Firstly, bauxite is first purified to produce aluminium oxide; aluminium oxide is then dissolved in molten cryolite to lower the melting point and reduce the amount of energy needed for the reaction. The mixture is placed in an electrolysis cell, made from steel, and lined with graphite. The graphite lining acts as the negative electrode (cathode) with several large graphite blocks acting as the positive electrodes (anode). At the cathode, aluminium ions gain electrons (reduction) and molten aluminium forms at the bottom of the cell which is then siphoned off from time to time and fresh aluminium oxide is added to the cell. The reaction for this is Al3+ + 3e- -> Al. At the anode, oxide ions lose electrons (oxidation) and oxygen is produced. 2O2- -> O2 + 4e-. The carbon in the graphite anodes reacts with the oxygen to produce CO2. This wears away the anode which means it has to be replaced regularly. A lot of electricity is required for this process and is it very costly. Overall equation: 2Al2O3 -> 4Al + 3O2.

Question 33

How is iron extracted?

Answer 33

Iron is extracted in a large container called a blast furnace from its ore, hematite.

Question 34

What is the process of extracting iron from hematite in a blast furnace?

Answer 34

The raw materials iron ore (hematite), coke, (an impure form of carbon) and limestone are added into the top of the blast furnace. Hot air is blown into the bottom. Zone 1: coke burns in the hot air forming carbon dioxide. The reaction is exothermic, so it gives off heat, heating the furnace. Carbon + oxygen -> carbon dioxide. C + O2 → CO2 Zone 2: at the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide. Carbon dioxide has been reduced to carbon monoxide. Carbon + carbon dioxide → carbon monoxide. C + CO2 → 2CO Zone 3: carbon monoxide reduced the iron(III) oxide in the iron ore to form iron. This will melt and collect at the bottom of the furnace where it is tapped off. Iron(III) oxide + carbon monoxide → iron + carbon dioxide. Fe2O3 + 3CO → 2Fe + 3CO2 Limestone (calcium carbonate) is added to the furnace to remove impurities in the ore. The calcium carbonate in the limestone thermally decomposes to form calcium oxide. Calcium carbonate → calcium oxide + carbon dioxide. CaCO3 → CaO + CO2 The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate. This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately. Calcium oxide + silicon dioxide → calcium silicate. CaO + SiO2 → CaSiO3