SB9 Material Cycles

Question 1

What are the two processes that allows water to enter the atmosphere as water vapour?

Answer 1

• evaporation
• transpiration

Question 2

What is the importance of the water cycle?

Answer 2

It distributes fresh water globally providing us with clean water for drinking

Question 3

Describe the water cycle

Answer 3

1. Water enters the atmosphere through transpiration or evaporation
2. The warmer air of the atmosphere rises, taking the water vapour with it
3. Since moist air cools down as it rises, water vapour forms clouds
4. Water returns to Earth in a form of precipitation

Question 4

Name the forms of precipitation

Answer 4

Rain, hail, snow or sleet

Question 5

Define potable

Answer 5

Drinkable water

Question 6

How can we produce potable water?

Answer 6

Filteration or chemical removal

Question 7

How do we provide potable water for regions experiencing droughts regularly?

Answer 7

Through desalination

Question 8

What is desalination?

Answer 8

Removing excess mineral ions from salts to make it drinkable

Question 9

What are the methods of desalination?

Answer 9

• Distillation
• Reverse osmosis

Question 10

Describe what happens in distillation

Answer 10

• saline water is boiled
• water vapour is funnelled through a tube before it is condensed
• pure water is collected

Question 11

Describe what happens in reverse osmosis

Answer 11

Saline water is forced at a high pressure through a partially permeable membrane which filters out all the mineral ions leaving pure water

Question 12

Give examples of materials that cycle through ecosystems

Answer 12

• water
• carbon
• nitrogen

Question 13

When is carbon removed from the atmosphere?

Answer 13

Photosynthesis by plants and algae - used to make carbs. When they are consumed, carbon moves up the food chain

Question 14

When is carbon returned to the atmosphere?

Answer 14

• When plants, animals and algae respire
• When combustion occurs

Question 15

What is the importance of the carbon cycle?

Answer 15

• component of all organic molecules, many of which are responsible for sustaining life on Earth, such as glucose
• since there is only a limited amount of carbon available, the carbon cycle is an essential way of recycling the carbon we have available to us

Question 16

Describe the carbon cycle

Answer 16

1. Carbon removed from atmosphere through photosynthesis
2. passed onto animals and decomposers due to feeding
3. returned through respiration; in plants, animals and decomposing microorganisms
4. additionally, returned by the combustion of fossil fuels

Question 17

What are the four key processes of the nitrogen cycle?

Answer 17

• nitrogen fixation
• ammonification
• nitrification
• dentrification

Question 18

Describe nitrogen fixation

Answer 18

Atmospheric nitrogen gas is converted into nitrogen-containing compounds such as ammonia, which forms ammonium ions (in solution) that can then be used by plants

Question 19

What is nitrogen fixation carried out by?

Answer 19

• Nitrogen fixing bacteria
• Lightning

Question 20

Describe nitrogen fixing bacteria

Answer 20

• found ‘free-living’ in soil and also in root nodules of certain plants (legumes)
• take n2 gas and change it into nitrates in the soil

Question 21

How does lightning play a part in nitrogen fixing?

Answer 21

Splitting the bond between two atoms and turning them into nitrous oxides like N20 and NO2, which disolve in rainwater and ‘leach’ into the soil

Question 22

Describe ammonification

Answer 22

Nitrogen compounds in waste products and dead organisms are converted into ammonia by decomposers

Question 23

Describe nitrification

Answer 23

Ammonium ions in the soil are converted into nitrates by the nitrifying bacteria

Question 24

Describe dentrification

Answer 24

Dentrifying bacteria use nitrates in the soil during respiration which releases nitrogen gas back into the atmosphere

Question 25

Define decomposition

Answer 25

Breaking down and digestion of biological material by organisms called decomposers

Question 25

What affects the rate of decay?

Answer 25

• temperature
• water availability
• oxygen availability

Question 26

Why is decomposition a crucial process?

Answer 26

It returns important materials back to the rnvironment, such as carbon and mineral ions

Question 27

How can decomposition be used in farming?

Answer 27

To make compost

Question 28

What is compost used as?

Answer 28

A natural fertiliser, as it recycles the previously used minerals

Question 29

What are the conditions required for decomposers to grow the best?

Answer 29

• warm
• moist
• lots of oxygen

Question 30

How can we preserve food?

Answer 30

• drying food: adding salt/sugar (removes water)
• chilling/freezing (removes warmth required)
• pickling (changes pH)
• canning/ vacuum packing/ sealing in gases like N2 (prevents oxygen access)
• irradiation: kills decomposers

Question 31

Define irradiation

Answer 31

Exposing something to radiation to kill microorganisms

Question 32

Stat the equation for the rate of decomposition

Answer 32

mass lost/ number of days

Question 33

What conditions ensure the best compost is produced?

Answer 33

• high temperatures: increase rate of enzyme controlled reactions
• water provided
• heap is turned to get more oxygen for the decomposers to respire

Question 34

How can farmers increase soil fertility?

Answer 34

• adding manure
• adding artificial fertilisers
• crop rotation

Question 35

How does manure increase soil fertility?

Answer 35

Increases the nitrates available in the soil

Question 36

How does crop rotation increase soil fertility?

Answer 36

Planting crops with nitrogen fixing bacteria and digging in the roots after the crop is harvested. Decomposers break roots down and release nitrates for the next crop