Page 35 - Curriculum Visions Dynamic Book

Air
Separating cover
Nitric oxide
catalyst: a substance that speeds up a chemical reaction but itself remains unaltered at the end of the reaction.
ozone: a form of oxygen whose molecules contain three atoms of oxygen. Ozone is regarded as a beneficial gas when high in the atmosphere because it blocks ultraviolet rays. It is a harmful gas when breathed in, so low level ozone, which is produced as part of city smog, is regarded as a form of pollution. The ozone layer is the uppermost part of the stratosphere.
smog: a mixture of smoke and fog. The term is used to describe city fogs in which there is a large proportion of particulate matter (tiny pieces of carbon from exhausts) and also a high concentration of sulphur and nitrogen gases and probably ozone.
EQUATION: Reaction of nitric oxide and air
Nitric oxide+ oxygen ➪ nitrogen dioxide 2NO(g) + O2(g) ➪ 2NO2(g)
 Nitric oxide is a colourless gas that is almost the same density as air. If a gas jar of nitric oxide is put together with a gas jar of air, and the separating cover slip pulled away, the nitric oxide will start to mix with the air (because gas molecules are constantly moving) and oxidise to brown nitrogen dioxide. Because nitrogen dioxide is heavier than air, it starts to sink.
Nitrogen dioxide
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