Everything on this worksheet is from BBC BITESIZE
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/oils/changesrev6.shtml
Earth and Atmosphere
The Earth is almost a sphere. These are its main layers, starting with the outermost:
Draw lines to label this diagram of the Earth
1. crust - relatively thin and rocky
2. mantle -- has the properties of a solid, but can flow very slowly
3. outer core -made from liquid n______and i______
4. inner core - made from solid n______and i______.
Plate tectonics
The Earth's crust and upper part of the m______are broken into large pieces called t______p______ These are constantly moving at a few c______each year. Although this doesn't sound like very much, over millions of years the movement allows whole continents to shift thousands of kilometres apart. This process is called c______d______.
The plates move because of c ______c______ in the Earth's mantle. These are driven by the heat produced by the decay of r______elements and heat left over from the formation of the Earth.
Where tectonic plates meet, the Earth's crust becomes unstable as the plates push against each other, or ride under or over each other. E______and v______e______happen at the boundaries between plates, and the crust may ‘crumple’ to form m______ranges.
Alfred Wegener
Alfred Wegener (1880 - 1930)
The theory of plate tectonics and continental drift were proposed at the beginning of the last century by a German scientist, A______W______. Before his time it was believed that the planet's features, such as mountains, were caused by the crust s______as the Earth cooled after it was formed.
It took more than 50 years for Wegener’s theory to be accepted. This was because it was difficult to work out what could make whole continents move, and it was not until the 1960s that enough evidence was discovered to support the theory fully.
Evidence for plate tectonics
So what was the evidence for Wegener's theory?
1. Plate tectonics explained why e______and v______were concentrated in specific places - around the boundaries of moving plates.
2. The match in s______between the east coast of S______A______and the west coast of A______suggests both were once part of a single continent.
3. There are similar patterns of r______and similar f______on both sides of the Atlantic - including the fossil remains of land animals that would have been unable to swim across an ocean.
Composition of the Earth's atmosphere today
The Earth's atmosphere has remained much the same for the past 200 million years. The pie chart shows the proportions of the main gases in the atmosphere.
The main gas is n______.
O______- the gas that allows animals and plants to r______, and fuels to b______- is the next most c______gas.
These two gases are both elements and account for about 99% of the gases in the atmosphere.
The remaining gases, such as c______d______, w______v______and n______g______such as a______, are found in much smaller proportions.
Evolution of the atmosphere
The early atmosphere
Scientists believe that the Earth was formed about 4.5 billion years ago. Its early atmosphere was probably formed from the gases given out by v______. It is believed that there was intense volcanic activity for the first billion years of the Earth's existence.
The early atmosphere was probably mostly c______d______, with little or no o______. There were smaller proportions of w______v______, a______and m______. As the Earth cooled down, most of the water vapour c______and formed the o______.
It is thought that the atmospheres of Mars and Venus today, which contain mostly carbon dioxide, are similar to the early atmosphere of the Earth.
Changes in the atmosphere
So how did the proportion of carbon dioxide in the atmosphere go down, and the proportion of oxygen go up?
The proportion of oxygen went up because of p______by p______.
The proportion of carbon dioxide went down because:
· It was locked up in sedimentary r______, such as l______, and in f______f______.
· It was absorbed by p______for p______.
· It dissolved in the o______.
The burning of f______f______is adding c______d______to the atmosphere faster than it can be r______. This means that the level of carbon dioxide in the atmosphere is i______.
Noble gases
Group 0
Argon makes up about 0.9 per cent of the air. It is one of a group of elements called the noble gases. The noble gases are in Group 0 of the periodic table.
The noble gases - Group 0
Properties and uses of the noble gases
The noble gases are all chemically u______gases. The table describes their main uses.
The main uses of the noble gases
Noble gas / Main use /Helium
Helium balloons / Used in b______and a______. It is much less d______than a___, so balloons filled with it f______u______.
Neon
Neon tube / Used in a______signs, it glows when e______is passed through it. Different coloured neon lights can be made by coating the inside of the glass tubing of the lights with other chemicals.
Argon
Blue light bulb / Used in l______b______. The very thin metal filament inside the bulb would react with o______and burn away if the bulb were filled with a___ instead of argon. Argon stops the filament burning away because it is u______
Krypton
Laser eye surgery / Used in l______. Krypton lasers are used by surgeons to treat certain eye problems and to remove birthmarks.
Test Bite
Top of Form
1. Starting with the centre of the Earth, what is the correct order for the layers of the Earth?
Core, mantle, crust
Mantle, core, core
Core, crust, mantle
2. What causes tectonic plates to move?
Convection currents in the mantle
Strong winds in the tropics
Sea water currents in the oceans
3. At what rates do tectonic plates move?
A few centimetres per year
A few metres per year
A few kilometres per year
4. Which is the most common gas in the atmosphere?
Oxygen
Nitrogen
Carbon dioxide
5. Which was the most common gas in the early atmosphere?
Oxygen
Nitrogen
Carbon dioxide
6. What is the approximate percentage of oxygen in the atmosphere today?
100 per cent
80 per cent
20 per cent
7. What caused the proportion of oxygen in the atmosphere to increase?
Respiration
Photosynthesis
Volcanic activity
8. Which of the following is a reason for the decrease in carbon dioxide in the Earth's atmosphere?
Its reaction with oxygen
It condensed to form the oceans
It became locked up in fossil fuels and sedimentary rocks
9. Why is helium used in balloons?
It is less dense than air
It is more dense than air
It has the same density as air
10. Why is neon used in neon lights?
It is coloured
It gives off light when electricity passes through it
It burns in air with a red flame
11. Why are the noble gases used in light bulbs?
They stop the filament burning
They make the bulb lighter to carry
They are cheap
Bottom of Form