Clean air Flashcards
What is clean air?
Air that has no pollutants caused by human activity
What are the main gases in clean air?
- Nitrogen
- Oxygen
- Carbon dioxide
- Water vapour
- Noble gases (argon, neon, krypton, xenon)
Which gas changes in air?
The amount of water vapour
Which gases remain almost constant in air?
- Oxygen
- Nitrogen
- Carbon dioxide
The levels of gases in the air depend on?
> Combustion of fossil fuels:
- Increases levels of carbon dioxide
- Decreases levels of oxygen
> Respiration by plants and animals:
- Increases carbon dioxide
- Decreases oxygen
> Photosynthesis by plants:
- Decreases carbon dioxide
- Increases oxygen
What are the percentages of the gases in clean air?
Nitrogen - 78%
Oxygen - 21%
Carbon dioxide - 0.035%
Argon - 0.965%
What is the word equation for respiration?
glucose + oxygen > carbon dioxide + water
What is the word equation for photosynthesis?
Carbon dioxide + Water > Glucose + Oxygen
How does combustion affect the levels of gas in the air?
It uses up oxygen, and makes carbon dioxide
Why has the levels of carbon dioxide in the atmosphere increases over the last few centuries?
> Deforestation- less photosynthesis
>Increased population- Energy requirements increased
Where do scientists know that gases came from?
At the centre of the Earth in a process called degassing
What is a theory of how the composition of gases came to be today?
> Original atmosphere had ammonia & then later carbon dioxide
Degassing of early volcanoes produced water & carbon dioxide
Chemical reaction between ammonia & rocks produced nitrogen and water
Condenses water then formed oceans
Carbon dioxide dissolved in ocean
Nitrogen levels increased due to its lack of reactivity
Organisms that could photosynthesis evolved which converted Co2 and water to oxygen
As oxygen increased, carbon dioxide decreased
Nitrogen slowly increased- very unreactive, so little was removes
What are pollutants?
Substances made by human activity that harm the environment
What are the three main pollutants in the atmosphere?
carbon monoxide, oxides of nitrogen and sulfur dioxide
Why are cars now fitted with catalyst converters?
They reduce the levels of carbon monoxide and oxides of nitrogen by converting it into carbon dioxide and nitrogen
