C13

Question 1

how many years ago was the earth formed

Answer 1

4.6 billion

Question 2

how do scientists know about the atmosphere from the past

Answer 2

using evidence from gas bubbles trapped in ancient rocks and data from atmospheres of other plantes

Question 3

what did volcanoes release that formed the early atmosphere

Answer 3

carbon dioxide, water vapour and nitrogen

Question 4

how did water come to earth

Answer 4

water vapour condensed as the earth cooled and fell as rain

icy comets rained down on the earths surface and melted bringing water to earth

Question 5

how were oceans formed

Answer 5

water collected in hollows in the crust as the rock solidified and formed oceans

Question 6

when did life on earth begin

Answer 6

3.4 billion years ago

Question 7

what were the first life forms on earth

Answer 7

simple organisms like bacteria. They used the breakdown of chemicals as a form of energy

Question 8

when did bacteria and algae evolve

Answer 8

2.7 billion years ago

Question 9

how was oxygen originally produced on earth

Answer 9

algae started photosynthesising to produce its own food and produced oxygen as a waste product

Question 10

how did oxygen become so prominent in the atmosphere

Answer 10

more plants evolved which produced more oxygen and removed carbon dioxide

Question 11

how does carbon end up in the skeletons and skulls of animals

Answer 11

carbon in glucose is released during photosynthesis and can end up in plant material which is then eaten by animals and some of the carbon transfers into their skeletons which then form sedimentary carbonate rocks

Question 12

how are sedimentary carbonate rocks formed

Answer 12

when skeletons at the bottom of the ocean become covered in sediment and form rocks under pressure

Question 13

how were fossil fuels formed

Answer 13

some animal and plant remains were crushed by large scale earth movements and heated in the earths crust forming coal, oil and gas

Question 14

how was coal formed

Answer 14

formed from thick deposits of plant material that died in swamps, were buried in the absence of oxygen and compressed

Question 15

how were oil and natural gas formed

Answer 15

from plankton remains deposited in muds on the seabed. remains were covered in sediment that became layers of rock when compressed over millions of years. crude oil and natural gas are trapped beneath these layers of rock

Question 16

how long have the proportions of gases in the earths atmosphere been similar

Answer 16

200 million years

Question 17

what are greenhouse gases and what are the main ones

Answer 17

greenhouse gases are gases that absorb energy radiated from it’s surface. The main ones are carbon dioxide, methane and water vapour

Question 18

how do greenhouse gases cause global warming

Answer 18

they absorb infrared radiation which stimulates the bonds in the molecules to bend, vibrate and stretch, raising their temperature (global warming)

Question 19

what is the carbon footprint of a product, service or event

Answer 19

total amount of co2 and other greenhouse gases emitted over it’s full life cycle

Question 20

what are 2 problems of trying to reduce global carbon footprint

Answer 20

restrictions could hinder poorer countries’ development as they are yet to industrialise

reductions have cost implications in manufacturing and transport industries

Question 21

what happens with sulphur in fossil fuels

Answer 21

reacts with oxygen when burned and forms sulphur dioxide. This causes acid rain which damages trees, kills aquatic animals and plants and attacks limestone buildings

Question 22

what happens when there is not enough oxygen in an engine

Answer 22

incomplete combustion occurs so co2 and co is formed. Carbon monoxide is a toxic gas that can kill humans

Question 23

what does high temperature in an engine cause

Answer 23

the normally unreactive nitrogen gas in the air reacts with oxygen making nitrogen oxide which can cause acid rain and trigger asthma

Question 24

how do diesel engines cause global dimming

Answer 24

they burn hydrocarbons with bugger molecules than petrol engines. When these molecules react with oxygen they don’t burn completely. The particles produced travel into the upper atmosphere reflecting sunlight into space which causes global dimming

Question 25

why was the first atmosphere of the earth lost

Answer 25

it was made from hydrogen and helium (like sapce today) these gases aren’t heavy and can escape the earth easily

Question 26

what allowed the ozone layer to be made

Answer 26

the abundance of oxygen in the early atmosphere

Question 27

what is the role of the ozone layer

Answer 27

stops harmful uv reaching the earth

keeps the planet cooler than it would otherwise be

Question 28

what 2 processes caused the percentage of carbon dioxide to decrease

Answer 28

photosynthesis by plants and algae
being dissolved by the oceans
production of sedimentary rocks eg limestone
production of fossil fules from remains of dead plants and animals