Tag Archives: kitchen oceanography: food related

Frost flowers on ice cream: When you start thinking about phenomena and something really annoying, all of a sudden, becomes really cool.

Frost flowers on ice cream. You must have seen them before: They sometimes occur when you’ve had some ice cream, put the left-overs back in the freezer, and take them out again. And there you have it: Water-ice crystals all over your lovely ice cream! Completely annoying because, obviously, they only taste like water and mess up your whole ice cream experience (or is that only me)?

You know I’m kinda fascinated with ice crystals on frozen blended strawberries, but last time I had some, there weren’t only crystalline structures, but there was frost on it:

Erdbeereis_1

Frost occurs when water vapour freezes without going through the liquid phase. Look at the awesome crystals!

Erdbeereis_2

Once I started thinking about the process that formed the ice and realised that those were actually frost and not just ordinary ice crystals, they all of a sudden stopped being annoying and instead became something that I kinda look forward to finding when I open a tub of my frozen blended strawberries. Because the structures are different every time, and really really pretty! And also how awesome is it to know that those ice crystals formed from water that wasn’t even liquid? Yes, this is the kind of stuff that makes me happy! :-)

Strawberry ice cream crystals

My new favorite thing is to put strawberries through a blender and then freeze small portions of that to eat as ice cream later. It is super yummy plus you never know what you’ll see when you open the lid!

Sometimes, you get long crystals like these:

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Ice crystals on strawberry ice cream

And then other times, you get something completely different. Look at those circular shapes! Perhaps that’s where the UFO landed? You can’t really see it in the picture, but those disks come quite a bit higher than the rest of the ice.

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Ice crystals on strawberry ice cream

In the bottom left corner, you see a smudge – that is where I pried off one of the disks to see what might have caused it. Turns out there is a cavity underneath. So somehow bubbles in the strawberry mash freeze out into those disks?

I am guessing that the ice cream in the second picture came from a batch that I beat harder than the one in the first picture, hence more bubbles. Or maybe the one in the first picture sat outside the freezer longer, so the bubbles had all reached the surface and popped before it went into the freezer? What do you guys think? Seems like I should really be carefully writing protocols next time I’m making ice cream! :-)

Vacuum pumps

What else did you think we tested them on?

Before using my parents’ vacuum pumps (“vacuum” being used in a loose sense of the word…) on water in this post, we obviously had to make sure they worked. And can you guess how you best test that?

Really. What else did you think we tested them on?

Happy Easter!

Tasting sea water reloaded

Doing the “tasting sea water” activity again with a different group of students.

A very good introduction to the concept of salinity is the “tasting sea water” activity. Last time I ran that activity, students were very quick to correctly connect the samples with the correct sampling locations without much discussion going on. This time round, though, there was a lot of discussion. Students quickly sorted samples in order of increasing salinity, but there was no agreement to be found on whether the Baltic or the Arctic should be fresher. Since I only pointed to a location and didn’t specify the depth at which the sample had been taken, some students argued that the Arctic was very fresh at the very top, whereas the Baltic was brackish. Others said that the Baltic was a lot fresher than any oceanic location.

salt-tasting

Students tasting four different samples of “sea water” with salinities corresponding to Arctic sea ice, the Baltic sea, the open ocean and the Mediterranean. Samples have to be associated with locations on a map.

In another group, there was a big discussion going on about how in marginal seas, evaporation or precipitation can dominate.

It is always great to see how much you can discuss and learn from an activity as simple as this one!

More on density

Extremely simple experiment to illustrate the effect of density differences.

At room temperature, will coke cans float or sink in freshwater? And how about coke light?

coke_cans

Soft drinks in cans. Who knew you could do science with them?

Btw, this experiment is only easy if you are in a country where you can get the right soda brand both in normal and in light version in cans. Thanks to Anna’s friends for importing them for me! As we found out – Red Bull does not work.