Form 1 Science Chapter 7

Air is mixture of several _____________.

• gases

• water

• dust

• vapour

• microorganisms

the content of air included nitrogen______%, oxygen_____%, carbon dioixide _____%, inert gases and other substances_____%.

the example of inert gases and other substances is ________.

• argon

• helium

• xenon

• neon

• krypton

the quantitiy of the components of air varies(变化) according to _________and_______.

important of carbon dioxide

• required in respiration

• required in photosynthesis

• radon to treat cancer

• used in fire extinguishers

• making carbonated drinks

green plants absorbs carbon dioxide to carry out ____________.

combustion of ________ that contain carbon like coal and petrol produces a lot of carbon dioxide and releases it into the atmosphere(大气层).

what is oxygen cycle?

• a continuous cycle takes carbon dioxide from the air and returns it to the air.

• is the cycle that maintains the content of carbon dioxide in the air by continuously taking carbon dioxide from the air and releasing it into the air.

• a continuous cycle takes oxygen from the air and returns it to the air.

• is the cycle that maintains the content of oxygen in the air by continuously taking carbon from the air and releasing it into the air.

the oxygen required for_______,except

• respiration

• combustion

• rusting

• photosynthesis

• decomposition

cause of interference of carbon and oxygen cycle

• greenhouse affect caused by volcanic eruptions releases sulphur gases and carbon

• forest fire cased by lightning produces large amount of greenhouse gases

• air pollutants such as fumes from vehicles and factories

• use of aerosol spray, refrigerators and air-conditioners which release CFC