C5.3

What are the current proportions of gases in the atmosphere?

About 78% nitrogen, 21% oxygen, and small amounts of other gases

What is one theory about the formation of the early atmosphere?

Volcanic activity released gases that formed it

What did volcanic activity release that helped form the oceans?

Water vapour that condensed

What was Earth’s early atmosphere similar to?

The atmospheres of Mars and Venus, mainly carbon dioxide with little or no oxygen

What other gases did volcanoes release into the early atmosphere?

Nitrogen, methane, and ammonia

How was carbon dioxide removed when the oceans formed?

It dissolved in water and formed carbonate sediments

How was oxygen added to the atmosphere?

Algae and plants produced it by photosynthesis

What is the word equation for photosynthesis?

Water + carbon dioxide → glucose + oxygen

When did algae first produce oxygen?

About 2.7 billion years ago

What happened after algae started producing oxygen?

Oxygen began to appear in the atmosphere

What caused the percentage of oxygen to increase over time?

The evolution of plants

How did algae and plants reduce carbon dioxide levels?

By photosynthesis

How else was carbon dioxide removed from the atmosphere?

By forming sedimentary rocks and fossil fuels

How was carbon trapped to form fossil fuels?

Living things were buried and exposed to heat and pressure

What did crude oil form from?

Remains of ancient plankton

What did coal form from?

Remains of ancient trees

What do greenhouse gases do?

Maintain Earth's temperature high enough to support life

Which gases are greenhouse gases?

Water vapour, carbon dioxide, and methane

What type of radiation is absorbed and emitted by the Earth?

Long wavelength radiation absorbed, short wavelength radiation emitted

How do greenhouse gases affect radiation?

They trap radiation emitted by the Earth

What human activities increase greenhouse gases?

Burning fossil fuels and deforestation

What do many scientists believe about human impact on Earth's temperature?

Human activities will increase atmospheric temperature causing climate change

Why is modeling global climate change difficult?

Because the system is complex

What can simplified models and media speculation lead to?

Biased opinions based on partial evidence

What is a major cause of climate change?

Increase in average global temperature

What are some potential effects of global climate change?

Melting ice caps, rising sea levels, extreme weather, and food shortages

What stages are assessed in Life Cycle Assessments (LCAs)?

Extracting raw materials, manufacturing, use, disposal, transport and distribution

What can be easily quantified in LCAs?

Use of water, resources, energy, and some wastes

Why is allocating values to pollutant effects difficult?

It requires value judgements, so it's not purely objective

How can selective LCAs be misused?

To support predetermined advertising claims

What reduces use of limited resources and environmental impact?

Reduction, reuse, and recycling of materials

Which materials are produced from limited raw materials?

Metals, glass, building materials, clay ceramics, and most plastics

Where does much of the energy for production come from?

Limited resources

What can glass bottles be reused for?

Crushed and melted to make different glass products

What happens to products that cannot be reused?

They are recycled for a different use

What is the carbon footprint?

Total greenhouse gases emitted over the full life cycle of a product, service, or event

How can the carbon footprint be reduced?

By reducing emissions of carbon dioxide and methane

What is a major source of energy for humans?

The burning of fossil fuels

What does the combustion of hydrocarbon fuels release?

Energy

What happens to carbon and hydrogen during combustion?

They are oxidised

What are the products of the complete combustion of a hydrocarbon?

Carbon dioxide and water

What is the general word equation for the complete combustion of an alkane?

Alkane + oxygen → carbon dioxide + water

How can complete combustion reactions of alkanes be represented?

By balanced symbol equations

Give an example of a balanced symbol equation for methane combustion.

CH4 + 2 O2 → CO2 + 2 H2O

What is a major source of atmospheric pollutants?

The combustion of fuels

What elements do most fuels, including coal, contain?

Carbon and

What gases may be released when a fuel is burned?

Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide, and oxides of nitrogen

What else may be released during fuel combustion that forms particulates?

Solid particles and unburned hydrocarbons

What are the characteristics of carbon monoxide?

It is toxic, colourless, and odourless

What effects do sulfur dioxide and oxides of nitrogen have?

They cause respiratory problems and acid rain

What problems do particulates cause?

Global dimming and health problems

What causes increased pollution related to population and living standards?

More resource use and waste production

Where can pollution occur?

In water, air, and land

What causes pollution when human waste isn’t properly handled?

Air pollution from smoke, land pollution from landfill rubbish, and water pollution from sewage and fertilisers

What can pollution do to animals and plants?

Kill or damage them, reducing biodiversity

What can be used to monitor the level of pollution in a habitat?

Indicator species

What are the main energy resources available for use on Earth?

Fossil fuels, nuclear fuel, biofuel, wind, hydroelectricity, geothermal, tides, the Sun, and water waves

How can pollution be reduced?

By using renewable energy resources

What is a renewable energy resource?

One that is being or can be replenished as it is used

How can some renewable resources be replenished?

By human actions or naturally

What is a non-renewable energy resource?

One that is not being or cannot be replenished as it is used

Do all energy resources have pros and cons?

Yes