C1- Air Quality

Question 1

Phase 2?

Answer 1

Green plants evolved and thrived over the earth. The early CO2 dissolved into oceans.

Green plants removed CO2 from the air and produce oxygen by photosynthesis.

When plants died and were buried under layers of sediment the carbon they had removed from the air became locked inside sedimentary rocks as insoluble carbonates and fossil fuels.

Question 2

Phase 3?

Answer 2

The build up of oxygen in the atmosphere killed off early organisms that couldn’t tolerate it.

It allowed more complex organisms to evolve. There is no CO2 left now.

Question 3

What are the chemicals in the atmosphere?

Answer 3

The earth is surrounded by a mixture of gases- the atmosphere. The atmosphere is made up of;

• Nitrogen 78%
• Oxygen 21%
• Argon 1%
• CO2 0.04%

Question 4

What are pollutants?

Answer 4

A chemical that’s harmful because it’s in the wrong place.

Pollutants come from different sources. (Burning fossil fuels,volcanoes)

Some pollutant gases are directly harmful to humans. They cause disease or even death in people who breathe in large enough quantities.

They can harm us indirectly by damaging our environment. (E.g. Acid rain-kills fish and trees)

Question 5

What are particulates?

Answer 5

They are tiny particles that are in the air.

Question 6

What are atoms and molecules?

Answer 6

All substances are made from tiny particles called atoms.

When atoms are joined together they make molecules.

Question 7

Describe air?

Answer 7

Air is a mixture of different gases which consists of nitrogen,oxygen,argon and carbon dioxide, made up of small molecules with large spaces between them.

Question 8

What are hydrocarbons?

Answer 8

The majority of fuels contain 2 elements- carbon & hydrogen. They are called hydrocarbons.

Many hydrocarbons are fossil fuels- made from the remains of dead plants and animals over millions of years.

Question 9

What are hydrocarbons used for?

Answer 9

Fuels such as petrol,diesel fuel and fuel oil are all mixture of hydrocarbons.

A hydrocarbon is a compound of only hydrogen and carbon

The only difference between different fuels is the size of the hydrocarbon.

Question 10

What is coal?

Answer 10

Coal is not a hydrocarbon. It is just carbon.

Question 11

What is combustion?

Answer 11

Combustion means burning, it is a type of chemical reaction. It is an oxidation reaction.

When a hydrocarbon burns the hydrogen atom in the fuel combines with oxygen atoms from the air to make hydrogen oxide. (Water)

Carbon atoms in the fuel combine with oxygen atoms from the air to make carbon dioxide.

When coal burns you get CO2:

Carbon+oxygen → carbon dioxide

Question 12

What is oxidisation?

Answer 12

Any reaction where oxygen is added is called oxidation reaction.

Reactions where oxygen is lost is called reduction reaction.

Hydrocarbon fuels burn more rapidly in pure oxygen than they do in air.

Pure oxygen are obtained from the atmosphere and kept in pressurised cylinders. The oxygen allows the fuel to burn rapidly so higher temperatures can be reached.

Question 13

How does carbon affect the atmosphere?

Answer 13

All fossil fuels contain large amounts of the element carbon. This creates pollution.

If a fuel burns where there’s lots of oxygen available- then all the carbon ends up as CO2.

If there’s not enough oxygen available (like in a car engine) the small amounts of carbon monoxide and small particles of carbon are produced.

Question 14

Carbon dioxide?

Answer 14

• The molecule has 2 oxygen atoms and 1 carbon atoms.
• It is an atmospheric pollutant. (it will stay in the atmosphere till its removed)
• CO2 can be removed naturally. Plants take in CO2 during photosynthesis. CO2 dissolves in lakes, rivers and oceans.
• However, human activity still increases CO2 levels.
• CO2 increases he greenhouse effect which warms up the earth.

Question 15

Carbon monoxide?

Answer 15

• The molecule has one oxygen atom and one carbon atom.
• It is produced when there’s not enough oxygen available when fuels burn.- this is called incomplete burning.
• It is poisonous- it can kill.

Question 16

Particulate carbon?

Answer 16

• When fuels burn incompletely particles of carbon are produced.
• When they escape into the atmosphere they float around.
• They then fall back to the ground and deposit themselves as soot
• Soot falls on buildings and makes them look dirty.

Question 17

What is sulphur?

Answer 17

When we burn fuels the super burns too. When sulphur atoms burn try combine with oxygen in the air to produce sulphur dioxide.

When power stations burn fossil fuels small amounts of polling sulphur dioxide are produced. It ends up in our atmosphere.

Sulphur dioxide has one sulphur atom and two oxygen atoms.

Question 18

How does sulphur cause acid rain?

Answer 18

• Sulphur stays in the atmosphere till something gets rid of it.
• Sulphur leaves in the form of acid rain.
• When sulphur dioxide emitted from car engines and power stations reacts with moisture in the clouds dilute sulphuric acid is formed.
• This acid will fall as acid rain:
• lakes become acidic
• kills plants and animals
• kills trees
• damages buildings & statues

Question 19

Nitrogen?

Answer 19

• Fossil fuels burn at high temperature causing nearby atoms in the air to react with each other.
• Nitrogen in the air reacts with oxygen in the air to produce small amounts of compounds called nitrogen oxides (nitrogen monoxide and nitrogen dioxide)
• This is happens in car engines.
• Nitrogen oxides are pollutants and are put into the atmosphere.

Question 20

Nitrogen monoxide?

Answer 20

• Forms when nitrogen and oxygen in the air are exposed to a very high temperature.
• This happens in car engines.

Question 21

Nitrogen dioxide?

Answer 21

• Once nitrogen monoxide is on the air it will react with more oxygen in the air to produce nitrogen dioxide.
• Nitrogen oxides stay in the atmosphere and react with moisture in clouds. They then produce dilute nitric acid which falls as acid rain.

Question 22

Reducing pollution?

Answer 22

• use less electricity
• use less fossil fuels
• more efficient engines
• catalytic converters
• pubic transport
• biofuels
• renewable resources

Question 23

Types of alkali used for wet scrubbing?

Answer 23

• Seawater- the sulphur dioxide is dissolved in seawater producing CO2, water and dissolved sulfate.
• A scurry- The scurry is sprayed onto the gases and sulphur dioxide reacts with calcium oxide. A solid waste product is formed (calcium sulfite)

Question 24

What are catalytic converters?

Answer 24

• They convert nitrogen monoxide into nitrogen and oxygen. (This is an example of reduction reaction)
• They convert carbon monoxide into carbon dioxide by adding oxygen (oxidation reaction)
• There are legal limits on the amount of pollution emissions that cars give out. Cars do MOT test once a year.

Question 25

Can biofuels run cars?

Answer 25

Car engines run by burning biofuels. They are renewable energy resources made from plants and waste.

They only produce CO2 and water when burned. Biofuels are carbon neutral as plants take in as much CO2 from the atmosphere as is given out by burning the fuel.

However, biofuels are resulting in species losing their natural habitats.

You can power cars using electric batteries. They produce no exhaust gases. You just recharge them. However, you still use electricity charging them.

Question 26

How did the early atmosphere form - phase 1?

Answer 26

The earths surface was originally molten for millions of years. It was too hot for any surface to form. Eventually the earth cooled and a thin crust formed. But volcano kept erupting.

The volcanos gave out gases including carbon dioxide, water vapour and nitrogen. This is how the atmosphere formed according to the theory.

The atmosphere was mostly CO2 and water vapour with no oxygen. The oceans formed when water vapour condensed when the earth cooled.