C20 - C21

Question 1

What is a hydrocarbon

Answer 1

Compounds that contain hydrogen and carbon only

Question 2

Describe what crude oil is

Answer 2

Crude oil is a mixture of hydrocarbons
Contains carbon chain molecules
Used for fuels
Finite resource

Question 3

How is crude oil separated

Answer 3

Crude oil is separated using fractional distillation , all the different hydrocarbons have different boiling points

Question 4

What are the different fractions in crude oil used for

Answer 4

Gasses - used in heating and cooking
petrol - used in fuel for cars
Kerosene - Aircraft fuel
Diesel oil - Fuel for cars and trains
Fuel oil - used in ships and power stations
Bitumen - used to surface roads and roofs

Question 5

How to hydrocarbons in different fractions differ from each other

Answer 5

the number of carbon and hydrogens
boiling points
ease of ignition
viscosity

Question 6

What is a homologous series

Answer 6

Have the same general formula
Differ from CH2 in every neighbouring compounds
Similar chemical properties

Question 7

Describe complete combustion of a hydrocarbon and the reaction for it

Answer 7

Happens when there is a good supply of air
Exothermic reaction

Hydrocarbon + oxygen = Carbon dioxide + water

Question 8

What does incomplete combustion give and why does it give this

Answer 8

Incomplete combustion gives : Carbon monoxide
Carbon
Water

This is because there is a poor supply of oxygen

Question 9

What are some problems of incomplete combustion

Answer 9

Carbon monoxide is a odourless , colourless and poisonous gas

Soot causes breathing problems and blackens buildings

Question 10

How is acid rain formed

Answer 10

Hydrocarbons naturally contain sulphur impurities

The sulphur reacts with oxygen to form sulphur dioxide

The sulphur then dissolves in water to form sulphurous gas

Sulphurous gas then reacts with oxygen to form sulphuric acid

Question 11

What are some problems of acid rain ?

Answer 11

Makes rivers and lakes acidic

reacts with materials such as limestone to weaken structures

Damages plants and trees

Question 12

What are some advantages of using hydrogen instead of petrol to power cars

Answer 12

Hydrogen has to be stored at pressure so it is difficult to store in a car
Not as durable as petrol engines
hydrogen is flammable

Good for the environment
produce more energy per Kg of fuel
water produced could have other uses

Question 13

What is cracking and how is it useful ?

Answer 13

Cracking is when larger hydrocarbons are broken down into smaller , more useful hydrocarbons .

It is useful as we can meet demand for the smaller , more useful , hydrocarbons . Alkenes produced are useful in the petrochemical industry

Question 14

How was the early atmosphere formed ?

Answer 14

From volcanic activity

Question 15

What did the early earths atmosphere contain ?

Answer 15

Little or no oxygen
A lot of carbon dioxide
Water vapour
Small amounts of other gasses - ammonia

Question 16

How were oceans formed

Answer 16

The earth started to cool after it formed
Water vapour condensed and fell as rain
Oceans formed

Question 17

How did the amount of carbon dioxide decrease when the earth was formed ?

Answer 17

Carbon dioxide is a soluble gas

when oceans formed , the carbon dioxide dissolved into the oceans

Question 18

How did the concentration of oxygen increase ?

Answer 18

Plants were starting to grow

Photosynthesis caused carbon dioxide levels to decrease and oxygen levels to increase

Question 19

Test for oxygen

Answer 19

a glowing splint relights in the presence of oxygen

Question 20

What is the greenhouse effect ?

Answer 20

Heat radiated from earth is absorbed by gasses
They then release the energy back into the earth
keeps the earth warm

Gasses are : Carbon dioxide
Methane
Water vapour

Question 21

What is climate change

Answer 21

When there are increased greenhouse gasses in the atmosphere , The global temperature increases .
this is bad as weather will be more extreme and sea levels will rise