1) May I ask for a piece of this wonderful cake? 2) We have a lot of work to do and so we'd like to have one more pair of hands. 3) This piece of chalk is very small, I cannot write with it. 4) Helena took a piece of paper and drew a beautiful flower on it. 5) I think you should wear the new pair of shoes to the party. 6) There were three thick pieces of bread on the plate. 7) That day I bought six pairs of beautiful Chistmas socks. 8) Peter was wearing a warm jacket and a strong pair of boots. 9) Sara couldn't see well and wore a pairs of heavy specs. 10) Listen! This is my favourite piece of music.
All the energy we receive , ultimately comes either from the sun or from the ground. The sun heats our planet , and supplies required for plant growth light . And in the distant past the sun in the same way our planet has implemented energy. His energy is transformed into plants , animal life supported . Due to this we get today coal, oil and natural gas - the so-called fossil fuel resources on which our civilization depends significantly . The only alternative energy source that is in the earth - the atoms of certain elements that formed long before the advent of the solar system. They are now in the crust * . * Uranium contained in the earth's crust , formed about 6.5 billion years ago, and its concentration is on average 0.14 %. Heat from the radioactive decay of uranium today manages the processes of convection in the Earth's crust. The amount of energy per unit mass of an atom depends upon the size of atom minimum amount of energy per unit mass of the atoms contained in the medium size ( such as carbon and oxygen) , while increasing the amount of the atoms contained in the small ( such as hydrogen ) or large ( such as uranium) . Energy can therefore be obtained either by joining smaller atoms atoms in average sizes (synthesis ) or by dividing the larger atom to medium size ( splitting). Development of fusion energy and humanity splitting energy is one of the most important achievements in the history .
