CC16

Question 1

What are finite resources?

Answer 1

A resource that is no longer being made or which is being made really slowly.

Question 2

What is crude oil?

Answer 2

Crude oil is a complex mix of hydrocarbons.

Question 3

What is a hydrocarbon?

Answer 3

A hydrocarbon is a compound that contains hydrogen and carbon atoms only. Carbon atoms can each form four covalent bonds, so the carbon atoms in hydrocarbon molecules are able to join together in different ways, forming chains and rings. The amount of carbon atoms in a hydrocarbon can vary from just one carbon atom to many hundreds of them.

Question 4

What state is crude oil in room temperature?

Answer 4

Crude Oil is liquid in room temperature.

Question 5

What is crude oil useful for?

Answer 5

Crude Oil is an important source of useful substances, including:
- Fuels for vehicles, aircrafts, ships, heating and power stations
- Feedstock or raw materials for the petrochemical industry

Question 6

What are petrochemicals?

Answer 6

Petrochemicals are substances made from crude oil, such as poly(ethene) and other polymers.

Question 7

What is natural gas?

Answer 7

Natural gas is a mixture of hydrocarbons in the gas state.

Question 8

What liquid fuels can be obtained from crude oil?

Answer 8

Several different liquid fuels can be obtained from crude oil, including petrol and diesel oil for vehicles, and kerosine for aircraft.

Question 9

How can crude oil be made useful?

Answer 9

Crude oil is usually not runny enough or ignited easily enough for it to be useful as fuel. The different hydrocarbons it contains must be separated into simpler, more useful mixtures. This can be achieved using fractional distillation because the hydrocarbons have different boiling points.

Question 10

How does fractional distillation work for crude oil?

Answer 10

The industrial fractional distillation of crude oil happens in a tall metal fractionating column.
The following steps occur:
1. Crude oil is heated strongly to evaporate it
2. Hot vapours are piped into the bottom of the column
3. The column is hottest at the bottom and coldest at the top
4. The vapours rise through the column and cool down
5. The vapours condense when they reach the part of the column that is cool enough (below their boiling points)
6. The liquid falls into a tray and is piped away
7. The vapours with the lowest boiling points do not condense at all and leave at the top of the gas as a mixture of gases
8. Bitumen has the highest boiling point and leaves at the bottom as hot liquid

Question 11

What are the separated liquid from industrial fractional distillation of crude oil called?

Answer 11

The separated liquids and gases are called oil fractions because they are only parts of the original crude oil.

Question 12

What are the oil fractions that come from fractional distillation and what are they used for (from top to bottom)?

Answer 12

• Gases (domestic heat and cooking)
• Petrol (fuel for cars)
• Kerosine (fuel for aircraft)
• Diesel oil (fuel for some cars and trains)
• Fuel oil (fuel for large ships and power stations)
• Bitumen (surfacing roads and roofs)

Question 13

What are the properties of oil fractions?

Answer 13

Question 14

What are alkanes?

Answer 14

Alkanes are hydrocarbons that only have single covalent bonds between the atoms in their nucleus.

Question 15

What are the compounds in crude oil fractions mostly?

Answer 15

The compounds in crude oil fractions are mostly alkanes.

Question 16

What is a homologous series?

Answer 16

A family of compounds that have the same general formula and similar properties, but have different numbers of carbon atoms.

Question 17

What do all homologous series’ have in common?

Answer 17

• The molecular formulae of neighbouring compounds differ by CH₂
• They have the same general formula
• They show a gradual variation in physical properties, such as their boiling points
• They have similar chemical properties

Question 18

What are the first three alkanes?

Answer 18

Methane, Ethane, Propane

Question 19

What is the molecular formula and structural formula for methane?

Answer 19

Molecular formula: CH₄
Structural formula:

Question 20

What is the molecular formula and structural formula for ethane?

Answer 20

Molecular formula: C₂H₆
Structural formula:

Question 21

What is the molecular formula and structural formula for propane?

Answer 21

Molecular formula: C₃H₈
Structural formula:

Question 22

What is a general formula?

Answer 22

A general formula represents the formula for a whole homologous series. The general formula for alkanes is: CₙH₂ₙ₊₂. This means that the number of hydrogen atoms is twice the number of carbon atoms, plus two.

Question 23

What is the trend of boiling points of alkanes?

Answer 23

The boiling point of alkanes increase as the number of carbon molecules increases. There is a gradual variation in this physical property though. This difference in boiling points of the alkanes is the reason why alkanes in crude oil can be separated by fractional distillation.

Question 24

What is complete combustion?

Answer 24

Complete combustion is combustion of hydrocarbons with enough oxygen present to convert all the fuel into carbon dioxide and water. It is a reaction in which:
- Only carbon dioxide and water are produced
- Energy is given out

Question 25

What do hydrocarbon fuels react with when they burn?

Answer 25

Hydrocarbon fuels react with oxygen in the air when they burn. This is called combustion.

Question 26

What conditions need to be present for complete combustion to occur?

Answer 26

Complete combustion happens when there is a plentiful supply of air or oxygen (e.g. when the air hole on a bunsen burner is fully open)

Question 27

What is the main hydrocarbon found in natural gas and what is the equation for complete combustion for it?

Answer 27

Methane. The equation is:
Methane (CH₄) + Oxygen (2O₂) –> Carbon dioxide (CO₂) + Water (2H₂O)

Question 28

How can apparatus be used to investigate combustion?

Answer 28

A pump draws combustion products from the Bunsen burner through the apparatus. Iced water cools and condenses water vapour passing through the U-shaped tube. White anhydrous copper sulfate in the U-shaped tube turns into blue hydrated copper sulfate, showing the presence of water. Limewater in the boiling tube turns milky, showing the presence of carbon dioxide (REFER TO PICTURE ON PAGE 270 OF TEXTBOOK FOR VISUAL AID)

Question 29

What is incomplete combustion?

Answer 29

Incomplete combustion happens when there is a limited supply of air or oxygen. During incomplete combustion of a hydrocarbon:
- Water is produced
- Energy is given out (but less than with complete combustion)
- Carbon monoxide (CO) and carbon are produced

Question 30

What problems can incomplete combustion cause in appliances that use hydrocarbon fuels?

Answer 30

Problems can arise if the appliances are poorly maintained or unventilated.
1. This is because it can release carbon monoxide (which is a toxic gas). It combines with haemoglobin in red blood cells, preventing oxygen combining. This reduces the amount of oxygen carried in the bloodstream, causing affected people to feel sleepy or to become unconscious. Severe carbon monoxide poisoning can even cause death.
2. Soot from incomplete combustion can block pipes carrying away waste gases from appliances. It blackens buildings, and it can cause breathing problems if it collects in the lungs.

Question 31

What is the pH of acid rain and why is it that acidic?

Answer 31

Acid rain has a pH lower than 5.2, making it more acidic than rain water. Sulfur dioxide is a major cause of this extra acidity.

Question 32

What does acid rain do?

Answer 32

1. Acid rain makes crops not grow well as the soil is too acidic from the rain.
2. Excess acidity in rivers and lakes prevents fish eggs hatching, and can kill fish and insects.
3. Acid rain increases the rate of weathering of buildings made of limestone or marble, and breaks down their structure.
4. Acid rain increases the rate of corrosion in metals, weakening them.

Question 33

What is weathering?

Answer 33

When rocks are broken up by physical, chemical or biological processes.

Question 34

What are oxides of nitrogen?

Answer 34

Atmospheric pollutants, usually represented as NOₓ.

Question 35

What does nitrogen dioxide form and what colour is it as a gas?

Answer 35

Nitrogen dioxide, NO₂, forms dilute nitric acid when it dissolves in water in clouds. Nitrogen dioxide is a toxic red-brown gas.

Question 36

What does Nitrogen dioxide cause?

Answer 36

Nitrogen dioxide can cause respiratory diseases such as bronchitis.

Question 37

How can oxides of nitrogen be made not harmful?

Answer 37

Catalytic converters in cars convert most of the NOₓ in exhaust pipes to harmless nitrogen.

Question 38

What is cracking?

Answer 38

A chemical reaction in which large alkane molecules are split into two or more smaller alkanes and alkenes .

Question 39

When is cracking used?

Answer 39

Oil refineries use cracking to match the supply of oil with the demand. This ensures that they don’t have extra supply of the oil for the demand that they have.

Question 40

How does cracking work?

Answer 40

Cracking involves breaking covalent bonds in hydrocarbon molecules. Crude oil fractions are heated to evaporate them. The vapours are passed over a catalyst containing aluminium oxide and heated to about 650°c. This speeds up reactions that break down larger hydrocarbon molecules. Smaller, more useful, hydrocarbon molecules form and these can be used as fuels or for making polymers.

Question 41

What is the difference between alkanes and alkenes?

Answer 41

• Alkanes are saturated (their carbon atoms are joined together by single bonds, C-C)
• Alkenes are unsaturated (they contain a carbon-carbon double bond, C=C)

Question 42

What state is petrol at room temperature and why is this useful?

Answer 42

Petrol is liquid at room temperature. This is useful as it means that large amounts can be stored in the car’s fuel tank and then pumped to the engine.

Question 43

Is petrol easily ignited and how much energy does its combustion release?

Answer 43

Petrol is easily ignited, and its combustion released large amounts of energy.

Question 44

Is hydrogen better for fueling cars than petrol?

Answer 44

Hydrogen can be used to fuel cars as it is a by-product of cracking. Hydrogen has environmental benefits because carbon dioxide is a greenhouse gas, linked to global warming and climate change, and the combustion of hydrogen does not produce any carbon dioxide.

Question 45

How can hydrogen be produced?

Answer 45

Hydrogen can be produced by reacting methane (from natural gas) with steam.

Question 46

What is a problem with storing hydrogen?

Answer 46

Hydrogen is a gas at room temperature. This makes hydrogen difficult to store in large amounts unless it is compressed under high pressure or liquefied by cooling.