gases in the atmosphere (38-40) (paper 1)
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what are the most prominent gases in the atmosphere
• nitrogen • oxygen
what percentage of air is nitrogen
78%
what percentage of air is oxygen
21%
what percentage of air is argon
1%
what percentage of air is carbon dioxide
0.04%
how can you investigate the proportion of oxygen in the atmosphere
using iron ~ rusts to remove oxygen from air
explain how iron can be used to investigate the proportion of oxygen in the atmophere
• soak iron wool in acetic acid & put in measuring cylinder • invert into a beaker of water • record starting position of water on cylinder • level of water will rise because iron reacts with water • leave about a week • record finishing position • ((start volume - final volume) / start volume) x 100
what is the formula for percentage of oxygen in air from the iron practicle
((start volume - final volume) / start volume) x 100
give three examples of elements that reacts with oxygen in air
• magnesium • hydrogen • sulfur
how does magnesium react with oxygen in the atmosphere
• magnesium burns with a bright white flame in air • white powder is formed = magnesium oxide • magnesium oxide powder is slightly alkaline when in water
how does hydrogen react with oxygen in the atmosphere
• burns very easily, can explode • almost invisble pale blue flame ~ product is water
how does sulfur react with oxygen in the atmosphere
• burns with a pale blue flame = sulfur dioxide • acidic when in water
what is thermal decomposition
when a substance breaks down into simpler substances when heated
what is produced when you heat metal carbonate
• carbon dioxide • metal oxide
what colour is copper (II) carbonate
green powder
when is produced when copper (II) carbonate is thermally decomposed
• carbon dioxide • copper (II) oxide
what is the word equation for the thermal decomposition of copper (II) carbonate
copper (II) carbonate -> copper oxide + carbon dioxide
what is the chemical equation for the thermal decomposition of copper (II) carbonate
CuCO3(s) -> CuO(s) + CO2(g)
how can you test is copper (II) carbonate has effectively thermally decomposed
collect the gas let off and test it for carbon dioxide
what type of gas is carbon dioxide
a greenhouse gas
how is Earth’s temperature created
by the balance of the heat from the sun and the heat Earth radiates back out to space
what is meant by the term greenhouse gas
a gas that absorbs most of the heat that would normally be radiated out into space and re-radiate it in all directions
what effects the amount of carbon dioxide in the atmosphere
human activity
give examples of how human activity can affect carbon dioxide levels
• deforestation • burning fossil fuels