[AllUnits]

Hello, for my school project for A Level I am planning to compare the amount of oxygen in different water samples. For example, comparing the amount of oxygen in sea water compared to fresh running water etc.

I have to write a lot about the science behind it as an introduction section to the report. The thing is, I have no idea what to write about.

Can anyone give me some wide areas that are related to what's going on with oxygen in water, for example, why different samples have higher/lower amounts? Why it dissolves in it? That sort of thing.

I realise this is quite an unspecific question, but any help would be greatly appreciated.

Regards.

[onenameless]

Well, oxygen in water is very insoluble. In air, oxygen makes about 21%, and if you were to take a litre of that air, you would find that 210ml of it is oxygen, but in water, only about 7ml of 1L of water is oxygen. Oxygen also varies in what type of water you examine. Freshwater tends to have less oxygen in it than does salt water. Some factors that effect its solubility are the temperature of water (do some research on this and compare amount of oxygen in cold vs. warm water) and pressure of solutes (search why salt water has more oxygen than freshwater). Pressure also has an effect, so look in to how much oxygen there is deep beneath the sea vs. near the top.