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Chemistry C1 > The earth and the atmosphere > Flashcards

The earth and the atmosphere Flashcards

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1
Q

Name the four layers of the earth from the center out…

A

Inner core
Outer core
Mantle
Crust

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2
Q

What is the inner core?

A

A solid ball of nickel and iron reaching temperatures of 5500 degrees C

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3
Q

What is the outer core?

A

A liquid layer made of nickel and iron reaching similar temperatures to the inner core

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4
Q

What is the mantle?

A

The widest section of earth which is approximately 2900km thick- made up of semi-molten rock called magma with a harder top and a softer lower part

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5
Q

What is the crust?

A

The thinnest layer of earth at up to 75km deep (30-40km under land mass)- made up of tectonic plates

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6
Q

How do we know the earth’s structure is like how it is?

A

Scientists use evidence from earthquakes-the way seismic waves travel is affected by the earth’s structure and density and mass

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7
Q

What are the current percentages of gases in our atmosphere?

A 
Nitrogen= 78%
Oxygen= 21%
Argon= 0.9%
Carbon dioxide= 0.04%
Other gases= 0.06%
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8
Q

What is the surface of the earth split into?

A

Tectonic plates

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9
Q

How do tectonic plates move across the earth’s surface?

A

Convection currents in the mantle

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10
Q

What happens where plates meet and when they rub against each other?

A
  • Volcanoes form
  • Earthquakes occur
  • Tsunamis may happen
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11
Q

How do convection currents work?

A
  • Radioactive decay in the centre of the earth produces a lot of energy
  • The energy heats up molten materials in the mantle
  • The heated part of the mantle expands, becoming less dense and rising towards the surface to be replaced with cooler material
  • This causes movement
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12
Q

Why are earthquakes and volcanic eruptions difficult to predict?

A

The plates move suddenly/unexpectedly quickly past each other

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13
Q

Name briefly the 3 phases of the evolution of the atmosphere

A

1) Volcanoes gave out gases
2) Green plants evolved and produced oxygen
3) Ozone layer allows evolution of complex animals

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14
Q

What was the earth’s early atmosphere made up of?

A

Mostly carbon dioxide with small amounts of methane, ammonia and water vapour

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15
Q

What happened in the early stage of the evolution of the atmosphere? (Volcanoes gave out gases)

A
  • The earth’s surface was molten so no atmosphere could be formed (as it just boiled away into space)
  • Eventually the surface cooled slightly but volcanoes kept erupting
  • The volcanoes gave out lots of gases (forming the atmosphere and oceans)
  • The oceans formed when water vapour condensed and the atmosphere was mainly carbon dioxide with no oxygen
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16
Q

What happened during the middle stage of the evolution of the earth’s atmosphere? (Green plants evolved and produced oxygen)

A
  • Green plants and algae formed over most of the earth
  • A lot of early carbon dioxide was dissolved in the oceans and green plants also absorbed it, producing oxygen by photosynthesis
  • Carbon and hydrocarbons were locked up in sediment from early marine shellfish and dead plants (becoming fossil fuels today)
17
Q

What happened during the later stage of the evolution of the atmosphere? (Ozone layer allows evolution of complex animals)

A
  • The build up of oxygen in the atmosphere killed off some early organisms but allowed other, more complex ones to evolve
  • The oxygen also created the ozone layer which blocked harmful rays of sun allowing even more complex organisms to form
  • There is virtually no carbon dioxide left now
18
Q

What are the 3 main theories for how life started on earth?

A
  • The Miller-Urey experiment (the earth’s early gases and state allowed life to begin)
  • Meteors crashed from space bringing life in the form of organic molecules (extra-terrestrial seeding)
  • Biological molecules could have been sourced from deep ocean near volcanic vents (with the chemicals and conditions required to make the building blocks of life)
19
Q

Explain the Miller Urey experiment and the evidence surrounding it

A
  • Used a mixture of water, ammonia, methane and hydrogen with a high voltage spark to stimulate a reaction like that of early earth creating amino acids
  • E. Possible to make molecules of life from gases that may have been in our early atmosphere
  • E. Amino acids are essential for making proteins and therefore life-with these conditions they found that amino acids had formed
  • Could have formed a primordial soup
20
Q

Explain the theory of extra terrestrial seeding and the evidence surrounding it

A
  • Meteors crashed from space to earth bringing life in the form of organic molecules which evolved elsewhere
  • E. In 1969 a meteorite fell from the sky above Australia (known as the Murchison meteorite) with a mass of over 100kg containing a range of organic molecules and amino acids
21
Q

Explain the theory of biological molecules being sourced from deep under the oceans and the evidence surrounding it (primordial soup links to the Miller Urey experiment theory)

A
  • Building blocks of earth- organic molecules could have formed a primordial soup and all molecules could have been in the sea
  • E. Near volcanic vents we get both the chemicals and conditions we need (MU)
  • E. Protein molecules are capable of replicating
22
Q

How can noble gases be useful?

A

They are unreactive and so can be used in situations to be safer than more reactive materials

23
Q

What are uses of helium?

A
  • Airships and party balloons: low density, floats in air, safer, does not react with oxygen to catch fire
  • Breathing mixture for divers (with oxygen): reduces chances of “bends”
24
Q

What are uses of argon?

A

Everyday lightbulb (filament): inert atmosphere inside bulb, no chemical reaction takes place between the metal filament and argon gas, stops filament burning away and makes light bulb last longer

25
Q

What are uses of neon?

A

Electrical discharge tubes/neon lights

26
Q

What is the continental drift theory?

A

In 1945 Alfred Wegener suggested that the continents had once been joined together but then slowly drifted apart

27
Q

What was Wegener’s evidence for the continental drift theory?

A
  • The shapes of the continents fit together like a jigsaw

- The types of fossils and rocks matched together when the continents were lined up

28
Q

Why were Wegener’s ideas not accepted at the time? (Continental drift theory)

A
  • No evidence for suggesting how the continents could move
  • Other scientists had different views and ideas
  • Wegener was not an expert geologist
29
Q

How do you separate gases in air?

A

Fractional distillation

Used to separate a mixture of liquids with different boiling points

30
Q

Explain the process of fractional distillation?

A
  • Gaseous air is cooled below -200 degrees C so it condenses to a liquid- achieved using high pressure
  • Pressure is released so air expands rapidly- this causes the temperature to decrease further so that carbon dioxide and water solidify so they can be removed
  • Liquid air is allowed to warm up, lower boiling point gases boil off at first and are separated
31
Q

What are some of the ways that earthquake and volcanic activity can be predicted?

A
  • Plates normally move slowly but a sudden release of strain energy causes earthquakes
32
Q

Why can’t scientists predict when earthquakes and volcanic activity will occur?

A

Can’t be certain …

  • about what is happening under the crust
  • where the forces/pressure are building up
  • about the size of the forces
  • when the forces will reach their limit
33
Q

Why has carbon dioxide decreased in our atmospheres?

A
  • plants/microorganisms
  • absorbed carbon dioxide in photosynthesis
  • dissolves in oceans
  • used to form the shell/skeletons of marine organisms
  • locked up as limestone carbonates
  • locked up as fossil fuels
34
Q

Why has oxygen increased in our atmosphere?

A
  • plants/bacteria

- releasing oxygen in photosynthesis

35
Q

Why has nitrogen increased our atmosphere?

A
  • ammonia reacted with oxygen

- bacteria/microorganisms release nitrogen

36
Q

Why has water vapour decreased in our atmosphere?

A
  • as earth’s temperature cooled, water vapour condensed to form oceans

Chemistry C1 (7 decks)

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