# Evaporating sea water

How much salt is there in sea water? What concentration do you need before crystals start forming? What will those crystals look like? I am sure those are the kind of questions that keep you awake at night!

Of course this can easily assessed experimentally. On a visit to the University of Bergen’s Centre for Science Education just now, I was shown the result of such an experiment: A litre of water was mixed with 35 grams of salt to simulate sea water with its typical salinity. Below, you see what the beaker looked like after sitting out for three months.

You can see that salt crystals are forming at the walls of the beaker, but that their structure depends on depth below the initial water level (see the 1000 ml mark on the beaker).

When there is still a lot of water in the beaker, crystals look like ornate flowers. Then, the less water is left in the beaker, the more square the crystals become. And at the bottom of the beaker, you see the typical salt crystals you would expect.

Actually, even though they look like the kind of salt crystals I would expect, apparently someone who knows about crystallography commented that there must be other stuff in there than just cooking salt since the crystals don’t look the way they should. I need to read up on this! :-)

Anyway, this is an experiment that I want to do myself, so maybe in three months time there will be more pictures of this!

Thanks for a very nice lunch, Olaug, Frede, Andreas, Morven and Elin! Looking forward to working with you a lot more in the future! :-)

P.S.: with this blog post I am testing to blog pretty much “real time” from my mobile phone, so if you notice anything odd, please let me know!

# The insulating properties of marshmallows

Ending hot-beverages-week in style.

So now we know how to cool down your tea by blowing on it and how to cool it down quickly (or not) by adding milk. So what if you wanted your hot chocolate to stay warm for as long as possible?

Yes! You should add marshmallows to prevent heat transfer both by evaporation and conduction.

Elsa, I’m pretty sure it was you I had that hot chocolate with back in 2011. Recognize your hands?

Actually, no matter what temperature you like your chocolate best at – you should always add marshmallows! :-)

For those of you who want to read more about marshmallows and ocean mixing, check out a very nice post here. For those others getting worried that I’ll only talk about tea until the end of time – nope! Tea week is now officially over and we’ll be back with “real oceanography content” pretty soon!

# Tea and milk

More physics applications  connected to tea.

After the frustrations of taking pictures of steam in my last post, I decided that I could use the very same cute mug to show other stuff, too. I know it has been done over and over again, but we have new students every year, don’t we, so someone has to keep telling the old stories, right?

So. When should you pour the milk into your tea? Right away or a little later?

Milk and tea

The answer, as you know, is “it depends”.

Do you want your tea as hot as possible? Then put the milk in right away and it won’t cool the tea down as much. Want the milk to cool down the tea as much as possible? Then wait for as long as you can before pouring it in.

The explanation behind this is of course that the cooling due to evaporation is happening faster the larger the temperature difference between the tea and the surrounding air. If you let it sit without milk, due to the larger temperature difference it cools down faster than if you poured in the cold milk, thus cooling it closer to room temperature, and then waited.

And there are even occasions when you would you put milk into the cup before adding the tea: If you have delicate china and don’t want to risk ruining it by pouring in almost boiling tea. Plus allegedly that way the milk doesn’t scald and form those weird flakes?