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We need to go back to our notebooks. We are on point number two, internal energy.

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So we are going to write it on our notebooks. And what do we need to know here?

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First of all, we need to know why the Earth is so hot.

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We have studied, and you have studied previous years, that the center of the Earth is really, really warm, really hot.

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actually the core is as hot as the surface of the Sun I suppose you have

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noticed it when you watch the video the other day okay so why does that happen

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why aren't we a cold planet for example Mars is not warm inside why does it

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happen okay let's see we have a primary source of all this heat and a secondary

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source of all this heat. So how do we need to do it on our notebooks? We need

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to have the center here, why is the center of the ocean hot? And here we make

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flaps. Okay and underneath we are going to write the information. Okay so let's

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see, let's start with the primary source. Okay I'm going to erase and you will

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right underneath. Okay, so let's see why we have a primary source of heat. First

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of all, the Earth was formed about 4,500 million years ago, and in that formation

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it happens that a lot of asteroid crash with each other, a small planet crash

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with another small planet, and there were a lot of collisions there to form the

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Earth. So that is the primary source of heat, when all those asteroid collided

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and the earth was formed so sorry so the primary source is the earth formation

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the earth formation okay as I said what is what does it happen on their

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formation that there is a collision of asteroids as I said it's not only

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asteroid that's also a small planet but still because of those crushings the

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is still warm inside but also there is a secondary source this secondary source

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start later after the formation of the earth okay here under the flap we need

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to write radioactive disintegration radioactive yes should go on by a new

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radioactive disintegration because in the core there are radioactive material

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for example uranium. This uranium starts disintegrating and it warms up

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the earth. The same that happens on a nuclear factory. Also in the core there

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is a lot of iron, iron and nickel, and this iron when it moves around, because

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we saw that there is some movement, there is some friction of the molecules

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of iron moving, so we have core friction, so radioactive disintegration and core

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friction, and because of this the earth is really really hot inside. We continue

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with 2.1 earth structure remember that all these parts need to be on the left

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side of your nodules and remember to fill in yes so parts of the earth okay

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the earth when we come into the surface okay imagine that we are here walking on

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the surface and we go to the center of the earth digging inside nobody has

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dig to the center of the earth nobody we can only study by all the things like for example earthquake

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but nobody has ever dig more than 10 kilometers down to the earth so no nobody has come to the

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core of the earth now we have different parts maybe are not the same that you have studied

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in previous years in primary school or in first professor but this is the modern theory of tectonic

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plates and you need to learn it, not the ones of a crust, mantle, core, no, that is very old,

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okay, we need something more new. Okay, so we have on the upper part the lithosphere,

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lithosphere, we have two types, oceanic and continental, and they have a different,

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they are not the same, okay, they are, they have different characteristics depending on

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if they are oceanic or continental these are the plates that are going to move on for the continents

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then underneath we have the sub-lithospheric mantle this is a mantle that is kind of

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like play-doh okay and it moves the mesosphere is right underneath this is what it used to be

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called mantle okay now it is sub-lithospheric mantle and mesosphere and the the change between

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the mesosphere and the outer core is called the double prime layer, okay?

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And it's a very important layer for the tectonic plates. Then we have the outer cord that we saw

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that it can form its fluid, okay? And the inner core that it has much much pressure and is solid.

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information please do the exercises