Tag Archives: kitchen oceanography

Surface tension and washing-up liquid

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How to destroy surface tension.

Remember how in this post my parents sent me a picture of the experiment that I didn’t get to work out?

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Stuff floating on an overfull cup of water. All because of surface tension.

Later the same day they sent me the movie below, demonstrating first how to put stuff on the surface without it sinking, and then how to destroy the surface tension using a tooth pick that is dipped in washing-up liquid.

Isn’t it curious how sometimes the surface tension breaks down right away and sometimes it doesn’t? I need might have to try this for myself again. Like right now. It’s bugging me so much that it didn’t work the first time round!

Surface tension and office supplies.

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Lots of stuff an be made to float on water just because of surface tension.

This morning, I was taking pictures of heaps of waters on coins. I was planning to follow up on that post with pictures of a dome of water on a full mug. So far so good.

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Surface tension preventing this over-full mug from overflowing.

Then, I was planning on putting paper clips on top to show how surface tension would keep them afloat.

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More surface tension.

Except it DID NOT WORK. Maybe there was dish soap residue in the glass? Maybe I was too clumsy? I have no idea what was wrong. Anyway, I was on the phone with my mom later that day, and within half an hour I had the picture below in my inbox.

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Paper clips and other stuff floating on the surface of a mug filled with water. All because of surface tension.

I guess you can make almost anything float on the surface if you put your mind to it… ;-)

Surface tension – heaps of water.

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The classical way of demonstrating surface tension.

When talking about surface tension, the classical thing to do is to talk about the shape of drops of water.

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Water drop on a coin.

As seen before in this post, the drops of water act as lenses.

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It is pretty amazing how much water you can pile on a single coin!IMG_6533

If you can’t see it from the photos, here’s a video. But rather than watching the video, you should try it yourself. It’s fun!

Refraction of light in water – coins and lenses.

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More on what water can do to light.

Remember my fascination with dandelions? Just to remind you:

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Dandelions.

Especially in combination with coins and water droplets, dandelions are a source of nearly endless entertainment:

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1 NOK with water droplet in the hole in the middle.

See how much cooler 1 NOK coins become only by adding a little water?

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The upper coin does not have water in the hole, the lower one does. See the difference?

Here the same two coins in the sun – see how the water droplet in the coin in the back focusses the light whereas the empty hole in the coin in the front is just a hole?

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The coin in the foreground doesn’t have water in the hole, the one in the back does. See how they affect light differently?

Pretty cool stuff. And in the next post I’ll show you what this very effect does out in the real world!

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Left coin without water, right coin with water in the hole in the middle.

Refraction of light in water.

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What water can do to light.

In the last post, I showed you a couple of pictures of a vase filled with dandelions.

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Dandelions and light being focussed by the water in the vase.

Turns out this might not have been enough of a clue, so here we go:

Isn’t it amazing time and time again how water refracts light and makes things look distorted?

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Refraction of light in water.

This can be used for all kinds of cool experiments, provided you have the right kind of coins at hand:

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1 NOK with a water droplet in the middle, acting as a lens. See how the dandelions are flipped upside down in the middle of the coin?

This kind of stuff keeps me entertained for quite some time!

Dandelions

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Making dandelion stem spirals.

It’s sunny, dandelions are everywhere and not every post on this blog has to be about oceanography in the strictest sense (although you’ll see the connection at the end of this post, I promise!).

But first, pretty pictures of pretty flowers.

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Dandelion.

As a kid, I could never understand why nobody wanted dandelions in their lawns – they are so pretty! Now I have my own lawn to look after and I am kind of starting to see the point, but still – they are so pretty! Plus you can do all kinds of cool experiments with them.

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Dandelion with cut stem

Which I did.

I forget how quickly the stem slices spiral up. Look here!

And if you kinda like doing this, but still want a connection to oceanography, look more closely at these pretty pictures.

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More dandelions with cut stems.

Can you see it? Let me give you a clue:

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Dandelions.

See it now? No? Oh well, you might just have to wait for the next post then…

Vacuum pumps

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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!

Bubble size depending on pressure

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More playing with a vacuum pump.

In this post, we talked about how decreasing the pressure on water can make dissolved gases come out of solution. But what happens if you suddenly increase the pressure again?

This is the same movie as in the previous post, just to remind you of what we did: We decreased the pressure and then let it increase again quickly (you hear the ssssssssssss when the air is streaming back into the bottle).

So to show it in one picture, what happens is basically this:

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Bubbles under low pressure (top) and high pressure (bottom). Screen shots from the movie above.

The lower the pressure, the larger the bubbles. When you let the air back into the bottle, the bubbles collapse (or shrink, if you want to be less dramatic).

That reminds me that I really need to film a movie similar to the one below where one can clearly see how bubble size increases the closer the bubbles come to the surface.

Isn’t it awesome to realize that the more you film and write and think about adventures in oceanography and teaching, the more ideas you have of what you want to do next? :-)

Gases dissolved in water

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A simple experiment to show that there are really gases dissolved in water.

Luckily, my parents like to play at least as much as I do. So when I got back from doing “real science” in Bergen the other day, they picked me up at the airport and showed me their latest toys: Vacuum pumps! [edit: Not really vacuum vacuum, but at least much lower than atmospheric pressure. And apparently those pumps are sold with the original purpose of re-sealing wine bottles]

Vacuum pumps are great to show that there are actually gases dissolved in water, because oftentimes that isn’t all that obvious. But when the pressure of the head space of a bottle is decreased, gases that were happily dissolved under atmospheric pressure start coming out of solution.

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Gas being bubbled out of water by decreasing the pressure of the head space of the bottle.

Here is a comparison of normal tap water and sparkling water (sparkling water obviously containing much more dissolved CO2 than tap water, hence more bubbling).

The insulating properties of marshmallows

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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.

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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!