The Atmosphere Today

The Atmosphere Today:

Gases in the Earth's atmosphere today :

Nitrogen - 78%
Oxygen - 21%
Argon - 0.9%
Carbon Dioxide - 0.04%
other gases - traces
[there is also water vapour but that changes too much from day to day so it is not included]

Some of the other 1% gases are unreactive noble gases, mainly argon. A small amount of CO2 is found aswell (0.04%). There are also trace amounts of other gases such as Carbon Monoxide, Methane, Nitrogen Oxides, Sulfur Dioxide.

The amounts of gases in the atmosphere may vary. For example -natural causes: volcanoes can release alot of sulfur dioxide and lightning can produce nitrogen oxides.

Human activity can also change the amount of certain gases in the atmosphere. 

• Deforestation means fewer trees to remove carbon dioxide from the atmosphere by photosynthesis
• Burning fossil fuels increases the amount of carbon dioxide, carbon monoxide and sulfur dioxide in the atmosphere
• Engines and furnaces can release nitrogen oxide
• Cattle and rice fields release large quantities of methane

Nitrogen is the main gas in the atmosphere today. There are different theories to where it came from

1) Volcanoes released nitrogen when the earth was young which means the atmosphere has always contained a lot of nitrogen

2) Nitrogen was added to the atmosphere gradually due to the reactions of nitrogen-containing compounds released from volcanoes.

Key Words:

Noble Gases

Trace

Deforestation

Questions:

1.Give two examples of human activity that could increase the amount of carbon dioxide in the atmosphere

2. List the thee main gases in the air, order of abundance

3. How does deforestation increase the amount of carbon dioxide in the air?

What you should know:

• 1.8 Be able to describe the current composition of the atmosphere and interpret data sources showing this information.
• 1.9 Be able to demonstrate an understanding of how small changes in the atmosphere occur through:
  • a) volcanic activity
  • b) human activity, including the burning of fossil fuels, farming and deforestation

Oxygen in the Atmosphere PCA

Oxygen in the Atmosphere PCA:

Oxygen is essential for humans.

Many substances , including metals, react with the oxygen in the air. Some react quickly and some slowly.

E.g / When Iron rusts it uses up oxygen in the air. Reactions like these can be used to find out the percentage of oxygen in the air.

Experiment:

How much air is used when metal reacts with it?

Hypothesis - 

About one fifth of the volume of air is oxygen

Apparatus and Chemicals - 

• Test Tube
• Beaker (100cm3)
• Ruler
• Iron Wool

Method - 

1 Put about 3 cm depth of iron wool into the test tube and wet it with water. Tip away excess water.

2 Put about 20 cm³ water into the beaker. Invert the test tube and place it in the beaker of water (see diagram). Measure the length of the column of air with the ruler.

3 Leave for at least a week.

4 Measure the new length of the column of air, taking care not to lift the test tube out of the water.

Rusting is an oxidation reaction of iron with oxygen.

iron + oxygen → iron oxide

What you should know:

1.7. Investigate the proportion of oxygen in the atmosphere

A Changing Atmosphere

A Changing Atmosphere:


As the earth cooled down, water vapour in the air condensed to form the oceans. Carbon Dioxide in the atmosphere then dissolved into the oceans. Scientists believe half of the world's carbon dioxide was lost through this way

Some marine organisms use dissolved carbon dioxide to make shells of calcium carbonate and as the creatures die their shells fall and become sediment. Over millions of years the layers of sediment compact to form sedimentary rock. 

Limestone is mostly calcium carbonate.

Scientists believe life started 4 billion years ago. About 1 billion years ago, some organisms developed the ability to photosynthesise.

Photosynthesis is taking in carbon dioxide, releasing oxygen.

Over time, more photosynthesising organisms evolved. Increasing levels of photosynthesis sped up the rate at which Carbon Dioxide was removed from the atmosphere and the rate oxygen was added to th atmosphere.

Key Words:

Sedimentary Rock

Limestone

Photosynthesise

Questions:

1. What is the main substance in limestone?

2. What are two ways carbon dioxide was removed from the early atmosphere?

3. Explain how the amount of oxygen in the atmosphere gradually increased?

What you should know:

• 1.5 Be able to describe how the amount of carbon dioxide in the atmosphere was reduced by:
  • a) the dissolution (dissolving) of carbon dioxide into the oceans
  • b) the later incorporation of this dissolved carbon dioxide into marine organisms which eventually formed carbonate rocks
• 1.6 Be able to explain how the growth of primitive plants used carbon dioxide and released oxygen by photosynthesis and consequently the amount of oxygen in the atmosphere gradually increased

The Early Atmosphere

The Early Atmosphere:

By studying other planets and moons scientists hope to find out more about the Earth's early atmosphere. They think evolution of life on Earth caused its atmosphere to change

Scientists are particularly interested in volcanoes because they release large amount of gases. Volcanoes, nowadays, mainly release Carbon Dioxide and Water Vapour.

So scientists believe these gases were in the earth's early atmosphere.

The atmosphere of Titan is 98% nitrogen , which some think were released by volcanoes. They think that this could have been similar to the world's early atmosphere.

 There are also volcanoes on Mars and Venus ( their atmosphere is mainly carbon dioxide). This make's some scientists believe the earths early atmosphere was that of Carbon Dioxide

However , Titan has a icy interior. Whilst Earth , Mars and Venus have a rocky interior; This makes it more likely the earth's early atmosphere was similar to that of Mars and Venus.

There was little or no oxygen in the early atmosphere. (volcanoes do not produce oxygen and the earth's oldest rocks would only form in the absence of oxygen)

As the earth became older , it cooled down. The water vapour in the hot atmosphere also cooled down and condensed into liquid water which formed the oceans.

Key Words:

Atmosphere

Questions:

1. Name the gases thought to have been in the Earth's early atmosphere and the evidence to support this

2. How is Titan's atmosphere different to that of Mars and Venus today?

3. Why haven't the atmosphere on Mars and Venus changed for billions of years, but Earth's atmosphere has?

What you should know:

• 1.1 Know that the gases produced by volcanic activity formed the Earth’s early atmosphere.
• 1.2 Know that the early atmosphere contained:
  • a) little or no oxygen
  • b) a large amount of carbon dioxide
  • c) water vapour and small amounts of other gases.
• 1.3 Know why there are different sources of information about the development of the atmosphere which makes it difficult to be precise about the evolution of the atmosphere.
• 1.4 Be able to describe how condensation of water vapour formed oceans.

Welcome

Hi,
This is a blog for all of you that need help revising for Edexcel Chemistry GCSE.

This particular blog is just for C1- Chemistry in Our World but in future I will try and create both a blog for C2 and C3. 

There are pages on the right, for each topic, where I'll link each completed post to. This will make it easier to find whatever you need help on.

Hope this helps all of you and you're all able to do well in any upcoming exams. 

Shakira