Chemistry GCSE AQA Year 10: Atmosphere

What are the proportions of gases in the atmosphere?

. 80% nitrogen

. 20% oxygen

. Small proportions of various other gases including CO2, water vapour, and noble gases

How long have the gases in the atmosphere been around the same as it is today?

200 million years

Why is evidence for the early atmosphere limited?

Because of the time scale of 4.6 billion years

What is the first step of one theory for the Earth's early atmosphere?

. In the first billion years of Earth, intense volcanic activity released gases that formed the early atmosphere and water vapour that formed early oceans

. At the start of this period the atmosphere may have been like those of Venus and Mars today, consisting mainly of CO2 with little or no oxygen gas

What is the second step of one theory for the Earth's early atmosphere?

. Volcanoes also produced nitrogen which gradually built up in the atmosphere

. There may have been small proportions of methane and ammonia

What is the third step of one theory for the Earth's early atmosphere?

When the oceans formed CO₂ dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of CO₂ in the atmosphere

How did oxygen increase in the Earth's early atmosphere?

. Algae and plants produced oxygen by photosynthesis

. Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere

. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve

What is the symbol equation for photosynthesis?

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

How did carbon dioxide decrease in Earth's early atmosphere?

. Algae and plants decreased the percentage of CO₂ in the atmosphere by photosynthesis

. Also decreased by the formation of sedimentary rocks that contain carbon

What is limestone?

. A sedimentary rock

. Mainly calcium carbonate

. Formed from the shells and skeletons of marine organisms

What is coal?

. A sedimentary rock

. Formed from thick plant deposits that were buried and compressed over millions of years

How were crude oil and natural gas produced?

. Remains of plankton were deposited in muds on the sea floor and were covered over and compressed over millions of years

. Produced crude oil and natural gas that became trapped in the rocks

What do greenhouse gases do?

. Maintain temperatures on Earth high enough to support life

. Allow short wavelength radiation to pass through the atmosphere to the Earth's surface but absorb the outgoing long wavelength radiation from the Earth causing an increase in temperature

What are 3 examples of greenhouse gases?

. Water vapour

. Carbon dioxide

. Methane

Which human activities increase the amount of carbon dioxide in the atmosphere?

. Combustion of fossil fuels

. Deforestation

Which human activities increase the amount of methane in the atmosphere?

. More animal farming (digestion, waste decomposition)

. Decomposition of rubbish in landfill sites

What does increased use of fossil fuels correlate with?

The increase in the percentage of CO₂ in the atmosphere over the last 100 years

What do many scientists believe will happen to Earth's atmosphere in future and what evidence do they have for this?

. Based on peer-reviewed evidence,

. Believe human activities will cause temp of Earth's atmosphere to increase at the surface

. This will result in global climate change

Why is it difficult to model global climate change?

It's a very complex system

What effect does global climate change being hard to model have?

Leads to:

. Simplified models

. Speculation and opinions present in the media that may be based on only parts of the evidence and which may be biased

What is a major cause of climate change?

An increase in average global temperature

What are the potential effects of global climate change?

. Sea level rise, which may cause flooding and increased coastal erosion

. More frequent and severe storms

. Changes in the amount, timing, and distribution of rainfall

. Temperature and water stress for humans and wildlife

. Changes in the food producing capacity of some regions

. Changes to the distribution of wildlife species

What is a carbon footprint?

The total amount of CO₂ and other greenhouse gases emitted over the full life cycle of a product, service or event.

What are some actions to reduce the carbon footprint?

. Increased use of alternative energy supplies

. Energy conservation

. Carbon capture and storage

. Carbon taxes and licences

. Carbon off-setting, including through tree planting

. Carbon neutrality - zero net release

What are some problems of reducing the carbon footprint?

. Scientific disagreement over causes and consequences of global climate change

. Lack of public information and education

. Lifestyle changes

. Economic considerations

. Incomplete international cooperation

What is a major source of atmospheric pollutants?

the combustion of fossil fuels

What do most fuels (including coal) contain?

. Carbon and/or hydrogen

. May also contain some sulfur

What gases may be released into the atmosphere when a fuel is burned?

. CO₂

. Water vapour

. Carbon monoxide

. Sulfur dioxide

. Oxides of nitrogen

What other than gases may be released when a fuel is burnt?

. Solid particles and unburnt hydrocarbons

. Form particulates in the atmosphere

What atmospheric pollutants are produced by incomplete combustion?

. Carbon monoxide

. Soot (carbon particles)

How is sulfur dioxide produced?

By oxidation of sulfur in fuel

How are oxides of nitrogen produced?

By the reaction of nitrogen and oxygen from the air at the high temperatures involved when fuels are burnt

What is harmful about carbon monoxide?

. Toxic gas

. Colourless and odourless so is not easily detected

. Combines with haemoglobin in the blood, reducing its capacity to carry oxygen

What is harmful about sulfur dioxide and oxides of nitrogen?

. Cause respiratory problems in humans

. Cause acid rain which damages plants and buildings

What is harmful about particulates?

. Cause global dimming, reducing the amount of sunlight that reaches Earth's surface

. Cause health problems for humans because of damage to the lungs