Gases in the atmosphere

Question 1

what are the 4 main gases

Answer 1

nitrogen
oxygen
argon
carbon dioxide

Question 2

approximate percentage of nitrogen gas in the atmosphere

Answer 2

78%

Question 3

approximate percentage of oxygen in the atmosphere

Answer 3

21%

Question 4

approximate percentage of argon gas in the atmosphere

Answer 4

0.9%

Question 5

approximate percentage of carbon dioxide in the atmosphere

Answer 5

0.04%

Question 6

EXPERIMENT to find % of oxygen using a non metal

Answer 6

• fill a trough with water and float an evaporating dish containing phosphorous
• measure initial level of water
• ignite phosphorous
• immediately cover with bell jar
• leave until flame extinguishes then measure final level of water
• (water will rise and replace volume of oxygen the reacted with phosphorous)
• compare water levels

Question 7

when finding out the % of oxygen, what do we need to be careful with

Answer 7

phosphorous as its toxic

Question 8

what equation do you use to find percentage of oxygen for non metal experiment

Answer 8

change in height of water / initial height of air x 100

Question 9

EXPERIMENT - how to figure out % of oxygen in atmosphere using metals

Answer 9

fill a burette up to the last mark with water

• empty it into a measuring cylinder and record the volume
• put wet iron filings into a burette
• invert it and place into trough of water
• record initial level of water
• leave until level of water stops changing
• record final level of water

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Question 10

what equation do you use to find percentage of oxygen for metal experiment

Answer 10

change in volume of water/ initial volume of air × 100

Question 11

what is combustion

Answer 11

scientific word for burning

Question 12

all combustion reactions involve a chemical change when oxygen reacts with elements which produces

Answer 12

OXIDES

Question 13

combustion reactions are ___ reactions because

Answer 13

exothermic

they give out heat

Question 14

observation of magnesium during combustion ( flame colour and what is produced)

Answer 14

intense white flame

White powder produced (magnesium oxide)

Question 15

observation of hydrogen during combustion ( what is produced)

Answer 15

its an exothermic reaction and water is produced

Question 16

observation of sulfur during combustion ( flame colour and what is produced)

Answer 16

blue flame

colourless, poisonous gas is produced

Question 17

symbol equation for combustion of sulfur

Answer 17

S (s) + O₂ (g) → SO2 (g)

Question 18

symbol equation for combustion of hydrogen

Answer 18

2H₂ (g) + O₂ (g) → 2H₂O (g)

Question 19

symbol equation for combustion of magnesium

Answer 19

2Mg (s) + O₂ (g) → 2MgO (s)

Question 20

what is thermal decomposition

Answer 20

term used to describe reactions where a substance breaks down due to the action of heat

Question 21

thermal decomposition of metal carbonates from (2)

Answer 21

metal oxide + carbon dioxide

Question 22

thermal decomposition of copper carbonate:

copper carbonate is a __(colour) powder which slowly ____ (colour) as ___-__– is produced

Answer 22

green powder

darkens

black copper oxide

Question 23

how can the carbon dioxide given off in thermal decompositions be tested

Answer 23

The carbon dioxide given off can be tested by passing the gas through limewater and looking for it to turn milky

Question 24

3 greenhouse gases

Answer 24

carbon dioxide
methane
water vapour

Question 25

what is the greenhouse effect

Answer 25

ultraviolet radiation is emitted from the sun and when it hits the earths surface, some is absorbed and some is re-emitted as infrared radiation - a lot of the infrared radiation is trapped in the atmosphere by the greenhouse gases which absorb and store the energy. - increasing levels of CO2 and methane cause upset to earths natural conditions because they trap extra heat energy