Samenvatting Water

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Samenvatting - Water

  • 1 Water reserves

  • Where can water be found?
    On the surface,, but also underground and in the air. 
  • In which states can water be found on earth?
    it, is next to sulfur, during the eruption of a volcano, the only substance found on earth in three different states of matter, solid (ice), liquid (water), and gaseous (water vapour) 
  • How many water is there estimated to be on earth?
    around 1.4 billion cubic kilometres. This amount of litres equals the number 14 followed by twenty zeros!
  • What amount is fresh water?
    2.5 %  is fresh water
  • What is the distribution of all fresh water?
    69% glaciers an permanent snowpacks
    30% fresh ground water
    0.3% fresh water in lakes and rivers 
    0.9% remaining fresh water, such as water in the soil, ice/caps permafrost and marshes 
  • What is the global sediment of rain and snow on earth?
    113.000 km2 of water
  • What will happen with this?
    This will partly evaporate and more than half of it will, through rivers, flow back into the ocean, without having been used. Also, one part in eight will fall in areas that are difficult to reach for humans. 
  • So what amount of fresh water is really available for animals, plants and people?
    at most between 9,000 and 14,000 km3 
  • If we compare the amount of water of 1994 to 1974 how has it decreased per person?
    there is only half the amount of water available per person.
  • How many of the population does not have the fulfill they need?
    one fifth
  • How many more water do we use than before?
    4x more than 50 years ago
  • What will happen with water during  the course of the century?
    it will become the scarcest natural resource for the production of food and for human consumption. 80% of the water we need is used for agriculture, the industry and the production of energy. Not efficient, less than half used effectively.
  • What can we do to improve the efficient use of water in a certain area or to increase supplies. 
    - use more economically. We can do with far less water, irrigate farmland more efficiently
    -build flood control dams and reservoirs for storing rainwater. 
    -surface water may be sourced from a different area, but the cost of transportation is very high.
    -you can drill for ground water, but after a while the soil may dry out
    -science enables us to win fresh water form salty water (desalination)
  • 2 Water a very special substance

  • Why do we need water?
    it influences our climate and the temperature on earth. That is why plants, animals and we, ourselves  need water to stay alive. Our industrial processes and our agriculture also depend on water. 
  • What are the four properties of water?
    1. density 
    2. specific heat capacity
    3. High boiling point
    4. Dissolving capacity 
  • Water molecules in ice are further apart than in water. The mass of one litre of ice is less than the mass of one litre of water. This means the density of ice is less than the density of water.  Makes Ice float on water. 
  • Explain the meaning of the sentence:'water has a high specific heat capacity".
    A lot of heat is needed to increase the temperature of one kilogram of water by one degree. 
  • In the summer the temperature of surface water will rise very slowly, and in winter it will cool down again very slowly.
  • What is the consequence of this?
    that in places on earth where you have a lot of water  the temperature will be fairly balanced.
  • If we compare water with methane, both have the same mass. How can you explain the high boiling point of water?
    In methane you will find van der Waals forces only, between the molecules. 
    Water molecules on the other hand have a small positive electric charge on one side of the molecule and a small negative electric charge on the other side. These water molecules will now attract each other and these electrical forces are much stronger than the van der Waals interaction. 
  • So why does it take such a long time to boil?
    To get water to boil, the water molecules need to let go of one another. In water much more energy is needed for this process than in methane. That is why water has a much higher boiling point than methane. 
  • Water is a very good solvent for many different types of substances. 
  • So water has a significant?
    dissolving capacity 
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Voorbeelden van vragen in deze samenvatting

Where can water be found?
1
In which states can water be found on earth?
1
How many water is there estimated to be on earth?
1
What amount is fresh water?
1
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