Cloud in a bottle experiment

Guest post by Susann Tegtmeier (written two months ago, I just never got around to posting it. Sorry!)

No one likes clouds when they bring rain, but what if you could make your own? Making a cloud inside a bottle will help us to understand how they are formed in the atmosphere. The experiment demonstrates how changes in air pressure, temperature and volume are related and how these changes can lead to the sudden appearance of tiny water droplets, or in other words, lead to the formation of a cloud.

You can do the experiment alone at home, in front of a classroom or as a hands-on experiment with all your students. I have chosen the latter option as part of my ‘Introduction to meteorology’ lecture for the first-year students in the Bachelor program ‘Physics of the Earth System’. For this class, Mirjam and I received funding from our university’s PerLe project for teaching innovations. We use the PerLe funding to consolidate the student’s physical-based understanding of the climate system through various experiments, exercises and discussions.

For the experiment you need an air-tight, transparent container that you can pump up with air (in order to increase the pressure inside the bottle). We made a simple version using materials from home including a plastic water bottle supplemented with valve from a bike tire that is attached between the bottle and the cap. Furthermore you need a pump (in our case a bike pump), water and matches.

Picture by Susann Tegtmeier

During the first round of the experiment, the students pumped up the bottles enhancing the pressure inside. During our discussion before the experiment, the students assumed correctly that the bottles would warm due to the enhanced pressure under a constant volume. By putting their hands around the bottles, it was possible for the students to feel that indeed the air inside the bottles was warming. When opening the valve slowly the opposite effect could be noticed and the bottles cooled very quickly. While the temperature change is small, it turned out to be quite fascinating and memorable for the students to see and feel the ideal gas law, they learned about earlier in class, in real life action.

During the second round of the experiment, the pumping up of the bottles was repeated, but this time with a small amount of water in the bottles. Since warm air can take up more water vapor than cold air, some of the water in the bottle was evaporated during the increase of pressure and temperature. While we discussed this effect during the experiment, it was, of course, not possible to observe the formation of the invisible water vapor. The next step of the experiment, the opening of the valve and the accompanying cooling of air, can theoretically lead to the condensation of the above discussed water vapor back to water. However, to the surprise of the students, no condensing little water droplets could be seen in the bottles.

Picture by Susann Tegtmeier

In order to lift the mystery, we carried out the third part of the experiment. With the bottle open, we lit a match and a moment later threw the blown out, smoking match into the bottle. Now the bottle needs be closed quickly before the same action (pumping of bottles and opening of valve) can be repeated. Only in this last round of the experiment, the expected water droplets became visible while the air was cooling. The reason is that small condensation nuclei are necessary for water vapor to condense and form water droplets. The experiment demonstrates this effect quite nicely in the bottle, but it also holds on large scales for the formation of atmospheric clouds.

The ‘Cloud in a bottle’ experiment is a perfect class room exercise, as it leads the students within 30 min from the basic, physical principles of the ideal gas law to one of the big climate effects, the aerosol – cloud interaction.

The energy lab’s dry run. Or: I have a great team! :-)

At first, I wanted to call this blog post “behind the scenes of a school lab” until I looked through the pictures and realized that all I am showing is people sitting around my desk in my office! Actually, not only sitting — test-running all the experiments for our energie:labor!

First, here is Julian’s experiment on atmospheric CO2.

And here an experiment from Jonas’ station on the role of the ocean in the climate system. A candle below an air-filled balloon. Can you imagine what will happen next?

Yes, this.

Sorry about the jump in perspective — even though I knew what would happen I clearly didn’t expect it enough to hold the camera stable. Small consolidation that everybody else clearly jumped, too?

Anyway, the point of that experiment is to look at the heat capacity of air and water. I’ve written about this before, see here (where we also have pictures of bursting the water-filled balloon because this is how we roll. But only in the lecture theatre, not in my office… ;-)).

Below, we are looking at Jonas’ overturning experiment, apparently discussing the work sheets. It’s really great how well this team works together on developing all their materials, even though their personal styles span the whole spectrum of teaching styles!

But we were also having fun, or at least that’s what it looks like… ;-)

In the picture below, taken on the second day of our dry run a couple of days later, we are looking at Henning’s station on the ice-albedo-feedback. As Henning is sitting next to me and we are sitting around my desk, he’s unfortunately not even in the picture!

In the background of the picture above you see the next exciting station that Nicolas prepared (and big shout out to my office mate who didn’t beat an eye when she came in and the office was filled with all our equipment and smelled of vinegar and white spirit…

What the guys are doing on the picture below? Using a bike pump to increase the pressure inside that bottle to make a cloud in a bottle.

Worked really well!

And then, there comes the most sophisticated piece of equipment of the whole lab: Nicolas’ cloud chamber. I’ll only tell you this much for now: It’s awesome! And you should stay tuned for an upcoming publication on how to build it and how to use it in teaching. Because it’s that great!

Now I’m out of pictures, but there is one last thing I want to say: Thank you, team, you are awesome! :-)

My new school lab on energy in the climate system has been launched! :-)

Today was a very exciting day: We launched my new school lab on energy in the climate system! The “energie:labor” is finally up and running again!

Let me walk you through some of the stuff that is going on in the lab.

Below, you see Mirko, who leads the station on the hydrological cycle, and his group working on an experiment.

In the left jar, you see how much smoke a burning piece of paper makes. The students tried this in order to compare it with the jar on the right. Because what they see in there is not just smoke from a burning piece of paper, it’s steam from the hot water at the bottom of the jar — a cloud in the jar! And the burning paper was just added to provide aerosols as condensation nuclei for the clouds.

Another part of the energy puzzle of the hydrological cycle: How much do raindrops falling down on the ground actually heat up the ground? The students are looking at the wooden board on the floor, using a thermal imaging camera. They won’t see a lot when the bouncing ball hits, but they saw a clear signal with the heavy metal ball they used earlier! Kinda like what we did at the European Researcher’s Night (see here).

Now, they are documenting their observations.

And later, they are running an experiment looking at how much moist vs dry air heats up in that insulated container below the lamp to explore the greenhouse effect of water vapour. The setup of this experiment was developed by Julian who is leading a different station on CO2 in the atmosphere, but sadly I don’t have any good pictures of that station!

On the table next to the hydrological cycle team, there is Jonas, working on the role of the ocean in the climate system. Below, the students are dunking air-filled bottles into hot and cold water baths to watch how air expands and contracts depending on its temperature.

They seem to be having fun!

Later, the team at this station did an overturning experiment. I have tons of pictures of that experiment, because it is just super photogenic (or because I am just still fascinated every time I see it, who knows?)

They are using a very strong lamp to model the heating by the sun near the equator, and cold packs to cool near the poles.

And they seemed to enjoy playing with food dye!

We have two more stations (or three, including the CO2 station I mentioned above), one on clouds run by Nicolas, and one on ice-albedo-feeback run by Henning. Unfortunately I don’t have good pictures of those, either, but I will post pictures of our trial run soon, where they’ll be featured, too.

Let’s close this by looking at how we brought all our new experts back together (because each group only conducted one station, for which they had almost all morning) — by using the Monash Simple Climate Model! I’ve written before about how great it is in teaching (see here), and I am still a big fan!

The new “experts” on clouds, the ocean, the hydrological cycle, atmospheric CO2 and ice-albedo feedbacks explained their topics to the rest of their groups. And — surprisingly enough — in the model, you can switch on and off each of these processes individually and see what effect it has on climate!

I think this worked really well to engage students in discussions about the processes they had just explored, and how they work together. Although I want to work on the kind of questions that guide them through the model before the next class visits the school lab in January…

But all in all, I am very happy with how the launch went, and I am super grateful to my great team! Thanks, Jonas, Julian, Nicolas, Mirko, and Henning (from the left in the picture above)! Hope you are enjoying your well-deserved weekend!

And last not least: Thank you, Frank, for letting us borrow your pupils! They were the nicest group we could have hoped for!

Of cupcakes and ice cores

For a popular science presentation on climate change, I needed a simple illustration for how ice cores can be used as archives of past climates. Luckily, my sister and family were excited to do some early Christmas baking for climate science!

And playing with food colors is always fun…

I think I had too much fun playing, actually, the “ice core data” would have been a lot easier to interpret if the different layers were just laying flat!

I should probably noticed here already that the color pattern wasn’t as regular as it should have been for easy interpretation of the core data later…

But it was fun! And they rose beautifully even though we were a little afraid that the time between mixing in the baking powder and actually baking the muffins was kinda long (because we had to mix in all the different dyes…)

The really difficult part, it turns out, was the coring itself. I had wider-than-usual straws, but instead of just cutting out the core, it was really difficult to have them pierce through the crust, and they compressed the core much more than I had hoped.

You can kind of see where the core goes in the cross section, and how the different colors correspond to their old locations inside the cupcake. But somehow this worked much better in my imagination than it did for real!

And I have a new-found appreciation for food bloggers. It’s really difficult to take good pictures of food!

But in case you were wondering: They taste just like boring, non-rainbow muffins. And my niece liked them! :-)

Observing the “melting ice cubes” experiment with a thermal imaging camera

Remember the melting ice cube experiment? Great!

Experiment: Ice cubes melting in fresh water and salt water. By Mirjam S. Glessmer

If I had the chance to teach an intro to oceanography or some other class where I have time with students over a longer period (these days I am mostly giving one-off workshops), I would actually use the thermal imaging camera to make a different point with this experiment than the one I have usually recommended it for.
I would first do the classical experiment to talk about density-driven circulation. This could be done either using dye (levels of difficulty would be something like 1) easy: freeze dye into the ice cube. 2) medium: let them observe what happens with clear ice cubes and only add dye once they’ve realized that the fresh water ice cube is melting much faster, but have a hard time figuring out why. In this case, drop dye onto the melting ice cubes. 3) no dye at all, but let people focus on condensation pattern on the cups as well as shapes of the ice cubes. I tried that for the first time a couple of weeks ago and it worked really really well. I think that’s my favourite way of doing the experiment now!
After students have done that experiment and we have moved on to properties of seawater etc weeks later, I would bring the same experiment back when talking about how water is transparent to visible light, but not to all other wavelengths. Because students will likely assume that they will see the same kind of pattern that they saw with dye (or that they sketched when they drew the mechanism), but actually, unless the plume of dense water is flowing right along the edge of the cup, they won’t be able to see it because they really only see the temperature of the cup itself and can’t “look inside” the way they can with their eyes. So at first, I would assume, they’d be a bit bored and annoyed to be presented with the same experiment again, until they realize that now the point is a very different one. (Since I haven’t tried to use that experiment in that way, I am not quite sure how it will work, I think it would be important to either hold the melting ice cubes in the middle of the beaker. That way, there is no cold plume along the edge of the cup, and students see cold water appearing at the bottom of the cup “out of nowhere”. Alternatively, one could ask them to look at the cup from the side opposite to where the ice cube is (they always float to the edge somehow), but maybe that would be giving too much away already?). So now the point would be to explain why we can’t see the sinking plume on the thermal imaging camera, and dependency of transparency of sea water on wavelengths of light. This can lead to ocean color, remote sensing, camouflage colors of animals, all kinds of other stuff. I think that could actually be exciting! What do you think?

Melting ice cubes & thermal imaging camera

I haven’t talked about my favourite experiment in a long time (before using it last week in the MeerKlima congress and suddenly talking about it all the time again), because I felt like I had said everything there is to say (see a pretty comprehensive review here) BUT! a while back my colleagues started playing with a thermal imaging camera and that gave me so many new ideas! :-)

I showed you this picture yesterday already:

img_9381

Here we see ice cubes melting in fresh water and salt water (and my very fancy experimental setup. But I am pretty proud of my thermal insulation!). Do you know which cup contains which?

Here are some more pics: The ice cubes before being dropped into the cups. Clearly dark purple is cold and yellow/white is warm (see my fingers?)

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After a while (5ish minutes), the cold meltwater has filled up the bottom of the freshwater cup while floating on top of the salt water cup:

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Looking in from the top, we see that the ice cube in salt water hasn’t melted yet, but that the other one is gone completely and all the cold water has sunk to the bottom of the beaker.

screen-shot-2017-06-11-at-17-13-20

When you check out the movie at the bottom of this post, you will notice that this experiment doesn’t work quite as well as I had hoped: In the saltwater cup, the ice cube floats against the wall of the cup and for quite some time it looks like there is a plume of cold water sinking in the salt water. I’m not quite sure what’s going on there. If it’s showing up like that because the cup is such a good thermal conductor, then why is the “plume” directional and not spreading in all directions? If there really is a plume, then how did it get there? It shouldn’t be! So many questions!

There really can’t be a plume of cold melt water in the salt water cup. For my workshop last week I made the plot below (which, btw, I don’t think anyone understood. Note to myself: Explain better or get rid of it!). So unless the plume is cold salt water, there is no way anything would sink in the salt water cup.

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So maybe we are cooling the salt water around the ice cube which then sinks and shows up because it is close to the wall of the cup? We can’t look “into” the cup with a thermal imaging camera, we can only see the surface of the cup (See, Joke? Maybe it is useful after all to learn all that stuff in theoretical oceanography ;-)). That’s also why we don’t see a plume of cold melt water in the freshwater case like we see when we have dyed ice cubes and see the melt water plume, like below:

dyed_ice_cubes_02

Anyway. Here is the video, in which you sometimes see my finger, pushing the ice cube away from the beaker’s wall to finally get to a state that looks like what I wanted to show you above:

My workshop at MeerKlima.de

Today I ran a workshop at the MeerKlima.de congress in Hamburg: A congress for high school students, organised by a student committee. The large lecture theatre of the chemistry department at the University of Hamburg was crowded for the opening lecture by Mojib Latif:

For my workshop, however, we set a limit of 40 participants due to the size of the room (and the amount of stuff that I had lugged in from Kiel. Yesterday’s ice cubes did very well, btw!). And there were two TV crews and a photographer documenting the awesome ice cube experiment.

You can watch documentaries of the workshop here and here (both in german).

Sneak peak of those two documentaries, obviously only of the tiny little sequences featuring me:


And thanks to Johanna and Dirk for their support before, during and after the workshop!

I also got to watch another workshop by a colleague, who used the Monash Simple Climate Model (which I have talked about here) and I have got to say: That is such an awesome tool for teaching about models and/or the climate system! You will definitely hear more about it in the future as I incorporate it into my own teaching.

And last not least we had a phone call to the Meteor off Peru which rounded off a day full of bumping into people I hadn’t seen in a while. Always great to reconnect with old friends and colleagues!

It was great fun to be part of this congress, and it was a great way to experience first hand how science outreach can work in such a format. Since the congress was curated by the students themselves, many students were very interested and asked great questions. Also, the topics of the workshops corresponded closely to what students really wanted to see and hear. It would be amazing to see this scaled up next year, maybe over several days and with more parallel sessions, so that participating students really get to pick and choose exactly what topic they are interested in and that even more students get the opportunity to experience such an amazing congress!

Workshop prep and a riddle

Looking at the picture below, can you guess which experiment I am going to do at the MeerKlima.de workshop? Yep, my favourite experiment — melting ice cubes! :-)

And I am obviously prepared for several extensions of the classic experiment should the students be so inclined…

Now I only need to get the ice cubes from Kiel to Hamburg — and as ice cubes, not a colourful, salty, wet mess :-)

Having gotten that backstory as a hint, any idea what’s going on with the spoons below?

Yep. Freshwater on the left, salt water on the right. Different refraction indices due to different densities. Neat :-)