Atmosphere and Oxygen

Question 1

What are the four main gases in our atmosphere?

Answer 1

Nitrogen, Oxygen, Carbon Dioxide, Argon

Question 2

What are the percentages of the four main gases in our atmosphere?

Answer 2

Nitrogen: 78%
Oxygen: 21%
Carbon Dioxide: 0.04%
Argon: 0.9%

Question 3

Explain four ways that the levels of CO2 have decreased in the atmosphere?

Answer 3

1. Trapped in fossil fuels
2. A reactant of photosynthesis
3. CO2 dissolved in the oceans
4. Skeletons and shells that contain CO2 build up in a layer of fine sediment

Question 4

Explain why levels of water decreased in the atmosphere

Answer 4

Temperature of the earth decreased. Water vapoured condensed and rained down to form oceans

Question 5

Explain why levels of nitrogen increased in the atmosphere

Answer 5

When ammonia reacts with oxygen, a product is nitrogen. Nitrogen is a very stable element so built up in the atmosphere

Question 6

Explain why levels of oxygen increased in the atmosphere

Answer 6

Oxygen was a waste product of photosynthesis in early evolved organisms

Question 7

Describe the experiment of Copper in Gas Syringes to determine the level of oxygen in the atmosphere

Answer 7

Powdered copper is weighed then put in a tube. Air in syringes pass over the copper whilst it’s heated. The mass of the copper is weighed once the volume of gas in the syringes has stopped decreasing. The copper has gained oxygen reacting to form Copper Oxide

Question 8

Describe the experiment of Red Phosphorus to determine the level of oxygen in the atmosphere

Answer 8

Phosphorus is placed in an evaporating basin in water in a bell jar. The phosphorus is lit and the lid is placed on the bell jar. Smoke forms in the bell jar. The water level rises by roughly 1/5 (20%) because the oxygen reacts with the phosphorus, using up the oxygen in the bell jar. It rises by 20% because oxygen makes up about 20% of the atmosphere

Question 9

Describe the process of fractional distillation

Answer 9

Liquified air is passed into the bottom of the fractionating column. The column is warmer at the top and colder at the bottom. Liquid nitrogen boils at the bottom and gaseous nitrogen rises to the top where it is piped off and stored. Liquid oxygen is collected at the bottom and piped out. (May also be used to separate argon from the oxygen as they have a similar boiling point)

Question 10

Recall one use of the following gases: Oxygen, Nitrogen, Carbon Dioxide, Helium, Neon, Argon, Krypton

Answer 10

Oxygen: Used in respiration
Nitrogen: Used in stainless steel manufacturing
Carbon Dioxide: Used in photosynthesis
Helium: Used in balloons
Neon: Traffic lights
Argon: Used in construction of lightbulbs
Krypton: Used in lighting and photography

Question 11

Is oxygen a reactive or non-reactive gas?

Answer 11

Reactive

Question 12

When an element reacts with oxygen, what does it form?

Answer 12

Oxides

Question 13

Write word equations for the reactions of elements with oxygen

Answer 13

Iron + Oxygen —> Iron Oxide

Carbon + Oxygen —> Carbon Dioxide

Sodium + Oxygen —> Sodium Oxide

Magnesium + Oxygen —> Magnesium Oxide

Sulphur + Oxygen —> Sulphurous Oxide

Question 14

Are metal oxides acidic or basic?

Answer 14

Basic

Question 15

Are non-metal oxides acidic or basic?

Answer 15

Acidic

Question 16

Describe the reactions of iron with oxygen

Answer 16

Sparks, Universal Indicator turns blue

Question 17

What are the three components of the fire triangle?

Answer 17

Heat, Fuel, Oxygen

Question 18

What are the methods for putting out flammable solid fires?

Answer 18

Water, Foam, Dry Powder

Question 19

Write word equations for complete combustion of fuels (e.g. Methane)

Answer 19

Fuel (E.g. Methane) + Oxygen —> Carbon Dioxide + Water

Question 20

Write word equations for incomplete combustion of fuels (e.g. Methane)

Answer 20

Fuel (E.g. Methane) + Oxygen —> Carbon Monoxide (or Carbon/Soot) + Water

Question 21

What are the two tests for water?

Answer 21

Cobalt chloride paper turns from blue to pink
Anhydrous copper (III) sulfate turns from white to blue

Question 22

State the test for Carbon Dioxide

Answer 22

Turns limewater cloudy/milky/chalky

Question 23

What are the methods for putting out flammable liquid fires?

Answer 23

Foam, Dry Powder, Carbon Dioxide

Question 24

What is the method for putting out flammable gas fires?

Answer 24

Dry Powder

Question 25

What are the methods for putting out Electrical Equipment fires?

Answer 25

Dry Powder, Carbon Dioxide

Question 26

What are the methods for putting out Cooking Oils & Fats fires?

Answer 26

Foam, Carbon Dioxide

Question 27

Describe the reactions of Carbon with oxygen

Answer 27

Carbon: Burns and forms a colourless gas, Universal Indicator turns red

Question 28

Describe the reactions of Sodium with oxygen

Answer 28

Burns with a bright yellow flame, Universal Indicator turns blue

Question 29

Describe the reactions of Magnesium with oxygen

Answer 29

Burns with a bright white light, Universal indicator turns blue

Question 30

Describe the reactions of Sulfur with oxygen

Answer 30

Sulfur: Neon yellow powder turns to a golden liquid, small light blue flame, UI turns pinky-red