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THE EARTH Earth story The story of the Earth began about 4500 million years ago when it was a hot ball moving around the newborn sun. Soon after, a giant rock with a size like Mars crashed into the Earth so violently that the rock melted, splashed off and cooled to become the Moon. As in the bellow sequence it is showed. Then the Moon was only 20.000 km far away from the Earth. The Moon is currently about 384.000 km away from the Earth. In fact, now the Moon is moving away from the Earth 3,8 cm per year.

The Earth was so shaken by the impact that all the elements in it separated. The dense metals, iron and nickel, collapsed to the centre to form its core, while lighter materials formed the Earth’s surface. In 500 million years, the Earth and the Moon, gradually cooled down and slowly, a hard crust of rock began to form. A1: How close was the Moon to the Earth when it formed? A2: How long does it take the Moon to increase the distance from the Earth in 1 meter?

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Layers of the Earth Use the computer to answer following questions: A3: Name the different layers of the Earth

A4: For each layer find its properties:

Layer Radius

Temperature

State (solid, liquid or gas). DENSITY.

Composition, name the most abundant elements

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The Earth’s crust Slowly, the Earth’s surface is moving all the time. Look at the map of the world and you will see, for example, that the west coast of Africa looks as if it would fit into the east coast of South America like pieces of a puzzle. The reason is that 220 million years ago – just before the age of dinosaurs – they were actually joined together. In fact, all the world’s continents were joined together in one huge landmass that the geologist name Pangaea. Pangaea gradually split up into today’s continents as plate movements caused earthquakes. The continents drifted to where they are today, CONTINENTAL DRIFT, and are still moving!! A5: Match the images with the date in order to explain the logical sequence of the Continental Drift.

a. 220 million of years (mya) b. 200 million of years (mya) c. 135 million of years (mya) d. Today

Picture 1 Picture 2

Picture 3 Picture 4

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It is not just the continents that are moving. In fact, the whole of the Earth’s surface is moving, including the ocean beds. The Earth’s surface is split into about 20 giant pieces called TECTONIC PLATES; 9 of them are huge and about 12 smaller. These plates are constantly on the move and the continents are embedded in this plates and move with them.

Key: A6: Find out the meaning of Convection Currents.

Plate boundaries pulling apart. DIVERGENT BOUNDARIES

Plate boundaries pushing together. CONVERGENT BOUNDARIES

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A7: Watch the following videos and try to explain why the tectonic plates are moving. http://www.youtube.com/watch?v=Ym7hrSPpuFE http://www.youtube.com/watch?v=0mWQs1_L3fA http://www.youtube.com/watch?v=ryrXAGY1dmE A8:

a. What do Convergent Boundaries mean?

b. What do Divergent boundaries mean? c. Where is new tectonic material

created? d. Where is tectonic material destroyed?

A9:

a. What is the cause of convection currents in the mantle?

b. Is the mantle completely solid? A10: Why is the oceanic crust always pushed underneath continental crust? A11: Now, check your answer in the table of page 2. Modify or add things that seem appropriate to you.

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The Earth Atmosphere The ATMOSPHERE that surrounds the Earth is thicker than the peel on the orange is. Without the atmosphere the Earth would be as lifeless as the Moon. The atmosphere absorbs the Sun’s warmth and protects the Earth from its harmful rays, as ultraviolet radiation. It gives us fresh water to drink and provides us with the air that we, and most other animals, need to breath. Our weather is also a result of the changes in the Earth’s atmosphere. These changes are caused by worldwide and local variations of the atmospheric temperature. Evolution of the Earth’s atmosphere For at least the first 2000 million years the Earth’s atmosphere was very poor in oxygen and N2, carbon dioxide, methane and water vapour were dominant constituent as it is shown in the graphic below. All of them were in gas state because of the high temperature. When the surface had cooled enough the water vapour condensed to form seas. Carbon dioxide persisted for some time. Part of the carbon dioxide was dissolved in seawater and it was in part was used by primitive organisms that developed photosynthesis capability.

The oxygen released by any volcanic or organic activity was quickly combined with other elements such as iron, aluminium, … to form oxides. When the first green algae appeared the photosynthesis process converted carbon dioxide into oxygen. Over time, the concentration of carbon dioxide was decreased. As more plants appeared, the levels of oxygen increased significantly while carbon dioxide levels dropped. With appearance of an ozone layer (a compound of oxygen atoms, O3), life forms were better protected from ultraviolet radiation from the Sun. A12: Use the graphic to answer the following questions:

a. When did the seas appear? Why? b. When did the green algae appear?

Current atmospheric composition As you know the atmospheric composition of Earth is 78% nitrogen, N2, and 21% oxygen, O2. Oxygen is the gas that we take from air to breath. A13: Use the computer to look for:

a. Atmospheric composition of Venus. b. Atmospheric composition of Mars.

Thousands of million of years

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The atmosphere has different layers and has an altitude about of 100 km, but the layer where we live are 12 km long. The Earth’s gravity “pulls” the atmosphere towards the Earth’s surface and its weight produce pressure on all things on Earth. Because of the atmospheric pressure, at sea level, the air’s density is about 1,2 g/L (grams per litre of air) and, for example, at 10 km above the Earth surface the density is about 0,4 g/L. The same happens with the temperature, at sea level the average temperature is 15ºC and at 10 km above would be -50ºC. A14: On a mountain of 7000 m altitude the air density is 0,6 g/L. How many litres of air must a mountain climber breathe to inhale the same amount of oxygen that exists in 1 litre at sea level? A15: Represent inside the squares the air molecules taking into account that there are 4 nitrogen molecules, N2, by each of oxygen, O2. Represent the air molecules at sea level and at 10 km altitude.

A16: Keeping in mind that the air density in our class is 1,2 g/L, how many kilograms of air are there in our class?

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The Carbon Dioxide, CO2, again As you know, carbon dioxide is a very important gas but the Earth’s atmosphere contains only 0,3% of carbon dioxide. Let us remember why is carbon dioxide so important: A17: Do you remember?

Use the picture below to answer the following questions:

a. Name other places or processes where carbon dioxide is produced.

b. How is carbon dioxide reduced from the atmosphere? A18: Is carbon dioxide a toxic gas? A19: What is the Greenhouse Effect?

N2, 78,4% O2, 20,8% CO2, 0,04% H2O vapour, 0,76%

N2, 75% O2, 15,3% CO2, 3,5% H2O vapour, 6,2%

Petrol, carbon

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Air pollution We say that the air is polluted when there are substances harmful to health in the air. The cities are the places where pollution is more important, it happens because of car engines, factories, heating systems, … and most of these things are concentrated in cities. Most of this pollution is linked to the chemical reactions of COMBUSTION. A20: Do you remember the chemical reaction when we burn petrol? Petrol + à + + Some of the most important gaseous pollutants are:

• CO, carbon monoxide. • SO2, sulphur dioxide. • NO, NO2. Nitrogen oxides • Some metals as, Hg, mercury, Pb, lead, Cd, cadmium.

A21: Use the computer to search how these gases are produced

• CO, carbon monoxide.

• SO2, sulphur dioxide.

• NO, NO2. Nitrogen oxides

• Some metals as, Hg, mercury, Pb, lead, Cd, cadmium. A22: Watch these videos and answer the following questions:

a. Is pollution always linked to a combustion process? b. Can our behaviour affect the environment?

http://www.youtube.com/watch?v=tmhiglxga-4 http://www.youtube.com/watch?v=TAbOVeKYgjU

A23: As a citizen,

a. Do you think you have a right to clean air and a clean environment? b. Do you think people should be punished for polluting?

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HYDROSPHERE. The water Scientists think that water has existed from the very beginning of the Earth, but as is shown on page 6, it was water vapour because the Earth’s temperature was higher than 100ºC. When Earth became cooler and the seas were formed, the seas’ composition were quite different from now, acids dissolved in water and reacted with rocks to produce salts as NaCl and others. Nowadays the salt in the seas has dissolved and the acids have disappeared because of chemical reactions. Remember: in a chemical reaction the initial substances disappear and form news substances. The water cycle The amount of water in the world remains constant, but is continually moving around the Earth and its atmosphere in a process called THE WATER CYCLE. The heat from the Sun causes the water to evaporate. As the water vapour rises into the atmosphere, it cools and condenses, then changes back into water, forming clouds. When the water in clouds becomes too heavy, it falls back to Earth as rain, precipitation, it can form snow or rivers, ending in seas and lakes, collection.

A24: Use the above picture to name the 4 main parts of the Water Cycle:

• A represents: • B represents: • C represents • D represents:

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A25: What makes the water cycle works? A26: In the opposite pictures, what process can we see? A27: What does Evaporation mean? A28: Why does seawater taste salty? A29: As you know, a great amount of seawater is evaporated, then why isn’t rainwater salty? A30: Why does water vapour condense when rising up in the atmosphere? What are clouds? Some of the rain soaks into the ground and is used by plants. Plants return unused water as it evaporates from their leaves, transpiration. A31: What would happen if you put a living plant in a closed glass box? The Water Cycle Rap: http://www.youtube.com/watch?v=i3NeMVBcXXU

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