Chapter 3 - Metals and their uses

Question 0

Describe two factors which shows if the extraction of particular metal is worth or not?

Answer 0

Whether it is worth extracting a particular metal depends on:
• how easy it is to extract it from its ore
• how much metal the ore contain

Question 1

Where do metals come from?

Answer 1

Metals are found in earth’s crust. We find most metals combined chemically with other chemical elements often with the oxygen. This means that the metal must be chemically separated from its compound before we can use it.

Question 2

Write down the metals which found in native state:

Answer 2

A few metals, such as gold and silver, are so unreactive that they are found in the earth as the metal (elements) themselves. We say that they exist in their native state.

Question 3

If there is enough metal in a rock to make it economic to extract it, what do we call the rock?

Answer 3

An ore.

Question 4

How do we extract metals?

Answer 4

The way that we extract a metal depends on its place in the reactivity series. A more reactive metal will displace a less reactive metal from its compounds. Carbon (a non metal) will also displace less reactive metals from their oxides. We use carbon to extract metals from their ores in industry.

Question 5

What is metal oxide?

Answer 5

The metal which is combined with oxygen is called metal oxides.

Question 6

What is reduction?

Answer 6

Removal of oxygen from a compound is called chemical reduction

Question 7

Write down the procedure of chemical reduction.

Answer 7

We find many metals such as copper, lead, iron and zinc combined with oxygen, these compounds are known as metal oxides. Carbon is more reactive than each of these metals so we can use carbon to extract these metals from their oxides.
We must heat the metal oxide with carbon, carbon removes the oxygen to form carbon dioxide. Metal is also formed as the element.
Metal oxide + carbon → Metal + carbon dioxide

For example;
2PbO + C → 2Pb + CO₂

Question 8

Describe the extraction of iron oxide.

Answer 8

Iron is less reactive than carbon so we can extract iron by using carbon to remove oxygen from the iron oxide in the ore. We extract iron in a blast furnace.
Some of the iron oxide react with carbon. The carbon reduces the iron forming molten iron and carbon dioxide gas. This is one of the reduction reaction which takes place in the blast furnace.

Question 9

Explain the difference between cast iron and pure iron.

Answer 9

Cast iron; iron straight from the furnace has limited uses. It contains about 96 % of iron and contains impurities mainly carbon. It makes it very brittle, although it is very hard and can’t be easily compressed. When molten, it can run into moulds and cast into different shapes. The cast iron used to make wood burning stoves, man hole covers on roads and engines.
Pure iron; removing all the impurities and carbon from cast iron gives us pure iron, this is very soft and easily shaped however it is too soft for most uses. If we want to make iron really useful, we must have to add tiny amounts of other elements such as carbon and metals eg chromium and nickel.

Question 10

What is an alloy?

Answer 10

Metal which is mixed with other element is called an alloy.

Question 11

Define carbon steel, and write down it’s uses;

Answer 11

The simplest steel is carbon steel. We make carbon steel by removing all impurities from cast iron, just leaving small amounts of carbon(from 0.3 to 1.5 %). This is cheapest steel to make and it is used in many products such as bodies of car, knives, machinery, ships and containers etc

Question 12

Write down types of steel.

Answer 12

Carbon steel; carbon steel is the cheapest steel and it contains between 0.3 to 1.5 % of carbon.
High carbon steel; It has relatively high carbon content, it is very strong but brittle.
Low carbon steel; It is soft and easy to shape, not very strong but less likely to shatter than high carbon steel.
Mild steel; it is easy to press into shape, it is used in production of car bodies.
Alloy steels;Low alloy steel; low alloy steel is more expensive than carbon steel as it contains from 1 to 5 % of carbon.
High alloy steel; high alloy steel is even more expensive than low alloy steel as it contains much higher percentage of other metals.
Stainless steel; the chromium nickel steels are known as stainless steel. It is used in cutlery and cooking utensils. They don’t rust.

Question 13

Why are aluminium and titanium are so useful?

Answer 13

When we need metals which are both strong and have low density, aluminium and titanium are often chosen. Theses are also metals which do not corrode.

Question 14

Write down properties and uses of aluminium;

Answer 14

Aluminium is silvery shiny metal. It is very light as it has low density. It is an excellent conductor of energy and electricity. We can also shape it and draw it into wires very easily.
Aluminium is not a particularly strong metal but we can use it to form alloys. These alloys are harder and more stronger than pure aluminium.
Aluminium is used in wide range of goods which includes;
Drink cans
Cooking foil
Saucepans

Question 15

Write down properties and uses of titanium;

Answer 15

Titanium is a silvery white metal. It is very strong and very resistant to corrosion. Like aluminium it has an oxide layer on its surface that protects it. Although it is denser than aluminium. It is less dense than most other metals. It has a very high melting point about 1660 C so it can be used at very high temperature.
It is used in;
Parts of jet engines
Parts of nuclear reactors
Replacement hip joints.

Question 16

Explain transition metals including their properties and uses;

Answer 16

In the centre of periodic table, there is a large block of metallic elements. They are called transition metals.
Properties;
Like all metals, transition metals are very good conductors of electricity and energy.
They are strong but can be bent or hammered into useful shapes.
Uses;
They are used in;
Buildings, cars, trains and other types of transport.
Heating systems and electrical wiring.

Question 17

Explain copper with its properties and uses;

Answer 17

Copper is very useful transition metal. It can be bent but is still hard enough for plumbers to use as water tanks or pipes. Fortunately, it does not react with water. Copper also conducts electricity and energy very well so it is ideal where we need
Pipes that will carry water or wires that will conduct electricity.

Question 18

Write down copper alloys;

Answer 18

Bronze was probably the first alloy made by humans, about 5500 years ago. It is usually made by mixing copper with tin. It is used to make ship’s propellers because of its toughness and resistance to corrosion.
We make brass by alloying copper with zinc. Brass is much harder than copper but it is workable. It can be hammered and press into intricate shapes. This property is used to make musical instruments.

Question 19

Write down aluminium alloys;

Answer 19

Aluminium has a low density for a metal. It can be alloyed with a wide range of other elements. There are 300 alloys of aluminium available. These alloys have very different properties. We can use some to build aircraft while others can be used as armour plating on tanks and other military vehicles.

Question 20

Write down gold alloys;

Answer 20

We can make gold harder by adding other elements. We usually alloy gold with copper when we use it in jewellery. Pure gold wears away more easily than its alloy with copper. By varying the proportions of two metals we also get different shades of gold object.