Tag Archives: kitchen oceanography

Fog and clouds in a bottle

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A little bit of hands-on meteorology for a change.

This post is inspired by www.planet-science.com‘s “fog in a bottle” and “make a cloud in a bottle” posts. Inspired meaning that I had to try and recreate their experiments after I saw this when approaching Zurich airport recently:

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Clouds and fog somewhere close to Zurich airport.

So let’s start with fog in a bottle. I’m doing fog in a jar, because it is easier to balance a sieve with ice cubes on a wide-mouthed jar than on a bottle… There is about 2 cm of hot water in the jar and the sieve with ice cubes is put on top to cool the moist air enough for fog to form.

And now the cloud in a bottle. This one is fun! And a lot more impressive in the flesh than in the movie, so try it out yourself! Suck some smoke into a bottle that contains a little water. Close the cap, press and release the bottle and see a cloud forming when you release it. The smoke acts as condensation nuclei here. And pressure changes, temperature changes, yada yada… Anyway, try it yourself!

P.S.: Kristin – erkennst Du die Flasche? Die, die Deine Freundin Dir mitgegeben hatte, damit Du was zu trinken hast, die dann mit in Göteborg war und die ich dem Recycling zuführen sollte? Hat offensichtlich nicht geklappt, aber viele Grüße an Deine Freundin! :-)

Tides in a glass

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A very simple experiment to show how waves can travel around an ocean basin.

I wrote these instructions for a book project that I was lucky enough to get involved in at the very last minute and figured I could just share them here, too. Why not try a new style every once in a while? You tidal purists out there – come up with a better experiment if you aren’t happy with this one! :-)

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  • Age: 6 years and above
  • Group size: 1-3 per group
  • Time: 15 min
  • Topic: Tides in enclosed basins 

Resources and Materials:

  • 1 clear plastic cup
  • 1 waterproof pen
  • water

Introduction:

[In a previous experiment] we have learned how tides are caused by the sun and the moon. In the picture there, we see the two “mountains” of water that form on either sided of the earth. The earth rotates underneath those two “mountains” of water, which is what causes high tides twice a day.

But what happens when those “mountains” of water reach a coast? Clearly the continents are not flooded twice a day every day, so the “mountains” of water cannot travel all the way around the globe undisturbed. What does happen instead is that the tidal wave will propagate around the rim of an ocean basin, even in semi-enclosed basins like the North Sea, which we will show in the experiment below.

  1. Fill the plastic cup approximately half full with water.
  2. Mark the still water level with a permanent marker.
  3. Gently start twirling the cup and observe how the water level starts changing: On one side of the cup it rises, on the other side it falls.
  4. Continue twirling the cup and observe how the “mountain” of water moves all the way round the cup, leaning against the side of the cup, and how opposite of the “mountain” a “valley” forms that also travels around the cup.
  5. Mark those two new water levels: The higher one is the high tide line of your ocean in a cup, the lower one the low tide line.
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Figure 1: Twirl a cup filled with water to see how tides propagate around an ocean basin

This is how high tide and low tide travel around an ocean basin. In the real world, though, coastlines are not as smooth as the walls of a cup, and also ocean basins are connected to each other, so tides in different basins interact. For a real world example, look at the tides in the North Sea, shown in Figure 2.

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Figure 2: Simplified timing of tides in the North Sea.

 

 

Ice cubes melting at the bottom of the beakers

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Because surely there is one more post in this topic? ;-)

For those of you who haven’t heard about the “melting ice cube” obsession of mine, please check out the links to other posts at the end of this post. For everybody else’s sake, let’s dive right in!

When Kristin and I ran the workshop at EMSEA14, a couple of people asked very interesting questions. One that I totally had to follow up on was this: What would happen if the ice cubes were forced to the bottom of the beakers? Of course we knew what theory said about this, but who cares? I still had to try.

If you have ever tried holding down ice cubes with straws…

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…and we have a movie of this! :-)

…you might know that that is quite difficult. So this is the experimental setup I ended up with:

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Ice cubes melting at the bottom of a fresh water and a salt water beaker

Zooming out a little bit, this is my fancy equipment:

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The camera gets a white skirt over the tripod because the reflection of the tripod is seriously annoying

Zooming out a little more, this is the whole setup:

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Chair on table in my winter garden, holding the white-ish oilcloth that serves as background. I should invest in a proper rod for the upper edge of the oil cloth, the current one has suffered a bit…

I know that some people want to try the experiment for themselves, so I’ll hide the rest of the experiment behind the cut, at least until Kristin tells me that she’s done it :-)

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Why folic acid might be good for people, but not so good for tank experiments

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I had to do the complete series of experiments, of course…

The other day I mentioned that I had used salt from my kitchen for the “ice cubes melting in fresh and salt water” experiment, and that that salt was the super healthy one that was both iodized and containing folic acid. And what happened is that the experiment looked like I was using milk. Not what I had envisioned.

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Ice cubes melting in fresh water (left) and in iodized-salt-with-folic-acid water (right)

Since I had often before used just regular table salt – which is usually iodized – I was intrigued by the opaqueness that seemed to be due to the addition of folic acid. Or was it? That I had never noticed the milky-ness of the salt water didn’t necessarily mean that it had not been milky before. So this is what the same experiment looks like if regular iodized table salt is used:

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Ice cubes melting in fresh water (left) and in iodized-salt water (right). Turbulence in the freshwater beaker due to me stirring (don’t ask)

In the literature it is always recommended to use kosher salt for experiments. Kosher meaning in this context that the salt should be only NaCl with no other additions. I happened to have some at hand after having bought it for the “teaching oceanography” workshop in San Francisco last year (after the salt that I brought for the workshop didn’t make it to the US. Long story). So this is what that looks like:

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Ice cubes melting in fresh water (left) and in kosher salt water (right)

In summary: Folic acid is what makes the salt water look opaque – but iodized salt is completely fine for tank experiments. I think it’s tiny air bubbles that cling to something folic acid-y, but I have no clue what is going on. I noticed that the dusty stuff settled down over night (so the top experiment here is a lot clearer than the experiment I ran with the same batch of water the day before), but even the next day the water wasn’t completely clear.

Anyway, now we know. And I came out of this series with more movies of ice cubes melting in fresh water and salt water!

Links to previous posts on the topic after the cut.

[Edit: Using my mom’s iodized, but not folic acid containing, table salt leads to milky water, too. So there you have it. I have no clue what is going on!]

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Melting ice cubes, again

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Somehow I am stuck on this demonstration!

I can’t let go of this experiment. Last time I posted about it, someone (Hallo Papa!) complained about the background and how I should set a timer and a ruler next to the beakers for scale. The background and timer I did something about, but the ruler I forgot. Oh well, at least there is room for improvement still, right?

I always find it fascinating to see how differently the ice melts in fresh water and salt water. Below you see how convection has completely mixed the fresh water with the melt water, whereas the melt water forms a layer on the salt water. You can even still distinguish horizontal currents in there!

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The beakers after ice cubes have melted in fresh water (left) and salt water (right)

For everybody who still enjoys watching the experiment: Here is a movie. Top one as time lapse, bottom one in real time, all 8 minutes of it. Enjoy!

The links to the “melting ice cubes” series after the cut.

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The icy elevator

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Weird things happening when ice cubes melt.

Remember I said that there were weird and wonderful things going on when I last ran the melting ice cubes in salt and fresh water experiment? It is really difficult to see in the picture below (sorry!) but you can probably spot the ice cube floating at the surface and the melt water sinking down, inducing some turbulence? And then there is a small ice bit a bit to the right of the center of the picture. And that ice bit is floating upwards.

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Dyed ice cube floating at the surface, and small ice bits floating up

Watch the melting ice cubes video below to see all the thing in action, it is visible really well as soon as the picture is moving:

So what is going on there? I think the solution to this riddle lies in me forcing ice to freeze even though it contains more salt (or in this case, red food dye) than it is happy with. Remember how dyed ice cubes look?

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Ice cubes frozen from colored water

So basically there is dye trapped in the middle of the cube, because cooling is happening from all sides, hence ice is starting to form from all sides, pushing the dye to the center of the ice cube. In the ocean, cooling would of course only happen from above, so salt is being rejected as brine.

Anyway, since I wanted to dye the ice cubes to make things more visible for this blog, I am adding a dissolved substance to the water that would usually not be there. Hence I am making the ice slightly denser than it would otherwise be. So when small ice bits chip away from the main cube (which still contains large parts of pure fresh water ice from the sides of the cube where, during the freezing, the dye could still be rejected; and which therefore still floats), they are denser than the water and sink. But as they melt, the dye washed out, and eventually the remaining ice is fresh, hence less dense, enough to float up again.

The whole thing looks pretty fascinating.

What do you think, is that the correct explanation? Or can you come up with a better one? Let me know!

P.S.: Everybody I showed this video to was fascinated by how the little piece of ice is floating up. But what I find a lot more fascinating is how it came to be at the bottom of the beaker in the first place! After all, ice is supposed to float on water (or drift up again if pulled down and then released) but how did it get down there???

Melting ice cubes reloaded

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Or why you should pay attention to the kind of salt you use for your experiments.

The melting ice cubes in salt and fresh water is one of my favorites that I haven’t written about in a long time, even though (or possibly: because) I wrote a whole series about it last year (see links at the end of this post).

Now that the EMSEA14 conference is almost upon us and Kristin and I busy preparing our workshop, I thought I’d run the experiment again and – for a change – take the time to finally know how much time to schedule for running the experiment. This is the experiment that I have run most often of all in all kinds of classes, but there you go… Usually I have more time than just 30 minutes, and there is so much other content I want to cover in that workshop!

There are a couple of things that I learned running this experiment again.

  • It takes at least 10 minutes to run the experiment. My water was slightly colder than usual room temperature, my ice cubes slightly smaller, though. And those 10 minutes are only the time the ice takes to melt, not the time it takes to hand out the materials and have the groups settle down.
  • There is a reason it is always recommended to use kosher salt for these kind of experiments. Look at the picture from one of the old posts in comparison to the ones from today: The iodized salt containing folic acid I had in my kitchen dissolves into really milky water. I really should have walked the two extra meters to get the good salt from my oceanography supplies in the other room!
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Ice cubes melting in fresh water (left) and salt water (right) – old experiment

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Ice cubes melting in fresh water (left) and salt water (right) – experiment today

  • Some food dyes are the devil. My whole kitchen is red. Plus the ice cubes didn’t freeze nicely (for a post on ice cubes freezing from salt water click here), the ice chipped when I tried to get the cubes out of the ice cube tray. I definitely can’t have that mess at a workshop. So here is another argument for using non-dyed ice cubes! The more important argument being that you think more if the cubes are not dyed and you don’t immediately see the explanation…

But it is always a fun experiment to run, and there are always new things to spot. Watch the video below and see for yourself! (Explanations on the weird phenomena coming up in a future post!)

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The links to the “melting ice cubes” series:

Ice cubes melting in salt water and freshwater (post 1/4)

Ice cubes melting in fresh water and salt water (post 2/4)

Melting ice cubes – one experiment, many ways (post 3/4)

Melting ice cubes – what contexts to use this experiment in (post 4/4)

Other posts on this experiment:

Dangers of blogging, or ice cubes melting in fresh water and salt water

Guest post: The mystery of the cold room

Salt fingering

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My absolute favorite experiment ever: salt fingering.

I know I’ve said it before about another experiment, even today, but this is my absolute favorite experiment and I still get endlessly fascinated. I’ve written about salt fingering before, and given tips on run the experiment, but today we tried a different setup.

We used the same tank as in the “influence of salinity and temperature on density“, put warm, dyed water on the one side of the dam and cold fresh water on the other side.

Contrary to Rolf’s advice, we didn’t aim for specific temperatures and salinities to hit the density ratio in a specific way, but just went for really hot and really cold.

We pulled the parting out, and after a couple of minutes, salt fingers started to develop.

Unfortunately, they are really difficult to take pictures of.

But a lot of students watched and will hopefully remember what they saw.

And even if not – I thought it was awesome and Rolf said they were the best salt fingers he had seen yet – even though we just winged it ;-)

Capillary effects

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When hydrostatics just doesn’t explain things.

Occasionally one notices water levels in straws that are slightly above the water levels in the glass. And of course – even though we always talk about water seeking its level and hydrostatics and stuff – we know that that’s how it should be because of the capillary effects. And then we probably all did that experiment in school where we had a very thin glass tube and the water rose really really high. But have you ever wondered how heights between straws with different diameters would differ? (Really? Only me?)

Anyway, here is how:

I do realize that the diameter of “typical” straws differs from country to country, but these are the Norwegian – and German – typical straws, so I herewith define this as universally typical. Anyway, from left to right: 8mm, 4mm and 3mm diameter on the outside. Unfortunately I don’t have the tools to measure the inner diameter. Plus I really need to get clear thin straws! Sorry the water level is so hard to see in the yellow straw – I even dyed the water for you!

But even with the imperfect materials I have – isn’t this quite an impressive result?

Btw, this is what it looked like when I did the experiment in my kitchen.

When in doubt, pile higher. And deeper.