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How much salt is there in the ocean?

Calculate how much salt the ocean contains (an optional activity)
6.3
PROFESSOR RACHEL MILLS: So we know there’s 35 grams of salt in every litre of seawater. And that’s what 35 grams of salt looks like. We have a bucket here of 10 litres of water, so there will be 10 times the amount of salt dissolved in there, 350 grams of salt dissolved in 10 litres of water. DR.
21.3
WILL HOMOKY: And just imagine how that would look if it was in the ocean. The ocean’s absolutely vast by comparison. In fact, there’s about 1.4 billion cubic kilometres of water out there. So if we were to dry down the amount of salt which is in that, just think how big that pile would be. It would be enormous.
In the previous step Where does the salt come from? Will Homoky explained that rivers contain only a tiny fraction of salt compared to the waters of the ocean.
Before we go on to investigate what else accounts for the difference, let’s take some time to think about:
  • How much salt is there in one cubic metre of seawater?
  • How much salt is there in the entire ocean?
  • If all the water in the ocean evaporated, how deep would the layer of salt left on the seafloor be?
Skip to the next step to see the answers to these questions – if you want to do the calculations yourself read on…

Your task

Download SALT CALCULATIONS AND ANSWERS at the bottom of this page. Do not scroll down too far if you are attempting the problems yourself and do not want to see the answers. You do not need to post your answers in the comments below – we will discuss them in the next step.
You can also look at the sheet, without attempting the calculations, if you just want to see how it is done.
The activity in the next step is about finding meaningful connections to the big numbers involved in these calculations; the results can be so huge that they seem very abstract.
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Exploring Our Ocean

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