Tornadoes, Hurricanes, Convection Currents, and Making a Barometer

You know you can't resist doing the ol' tornado-in-a-bottle activity! We did a couple variations on this. There are millions of resources for it online. We did the two-bottle version (two 2-liter bottles taped together at their mouths) and the jar version (like this), and I will say that I think adding the food coloring makes the tornado harder to see, so I advise against it. If you add glitter or other "debris," you can see things being pulled up by the vacuum in the center, which is kind of interesting.

I always wondered who on earth would buy these tornado tubes when you can just use tape---but our bottles leaked like crazy, so now I get it. If I were doing this repeatedly or with a whole class of students I'd invest in the tubes.

We've looked at water convection currents before, and air convection currents as well, but we did a quick review to precede our discussion on how tornadoes are formed. We also reviewed what we'd learned about vortices from our air vortex cannon. High- and low-pressure weather systems seem like they'd be simple to understand, and they ARE when you think in terms of air density and temperature, but I always have to talk myself very methodically through it to make sure I'm not mixing anything up.

Here's a good article about something that doesn't feel very intuitive---the fact that humid air (air with water in it) is actually lighter than air with less humidity. That means it doesn't push down as hard on the mercury or other fluid in your barometer, so the barometric pressure is lower. Again, this is easier if you actually picture a barometer. Lots of pushing from the air=barometer high, less pressure from the air=barometer low. Making our own barometer helped us keep this straight in our minds. It also helps me to think this: if the air is full of water, the actual air molecules have to be farther apart to fit the water between them, and therefore they exert less pressure on each other. More humidity=lower air pressure.

Here are two kinds of homemade barometers.

General idea for the water barometer here and the air barometer here. Our water barometer froze soon after this picture was taken, so I'd recommend the air one for colder weather! :)

Our friend Jena had the awful, but very interesting, experience of being IN a tornado! She was kind enough to send us some pictures, which were really fascinating to look at. There is something about seeing pictures from a real person instead of news reports---it makes the event seem so much more personal and real.

And here are some tornado pictures we liked from National Geographic.

Civil War Weapons, and Making an Air Vortex Cannon

Artillery Guns! How we love them. In fact, Abraham chose to do his Final Project on Civil War Artillery. They are really quite fascinating. We also became very interested in muskets and small arms. Did you know, for example, that rifling refers to the spiral grooves inside the barrel of a gun, which help the bullet spin and therefore go farther and straighter? Some older muskets used in the war were smoothbore (non-rifled) and didn't work nearly as well. This video shows a musket firing in slow motion---you can see the flash as the initial charge, and then the powder in the barrel, ignites. So cool! And here is a website that was very informative.

We made this chart during our discussion---there is a lot of weapons vocabulary that I never knew before! I never thought I could be so interested in guns.

We watched the end section of this video, which shows how a team of artillerymen loaded and fired cannons in the Civil War. (And we got to see real cannons fired here earlier!) Cannons are just one type of artillery gun, we learned. There are also howitzers and mortars, which have a higher angle of fire and usually fire shells instead of solid shot.

Anyway, I thought the perfect activity for our weapons day would be to make a cannon of our own---an air cannon, of course! We tried a couple designs (this was our first attempt) and thought this one worked the very best. (It is also the simplest; all you need is any size box, and packing tape. You cut a round hole in one side of the box, tape up all the other sides so no air can escape, and you're all set!)

Air cannons are so fun. We tried filling ours with flour and shaking it up to see if we could make the vortex visible, but it didn't work too well. We considered putting a candle inside to make smoke, but it seemed like too much trouble (and I didn't want to light the box on fire).

You can see a slight ring of flour dust in front of the cannon's hole

We had a great time playing around with our cannon. It was pretty powerful even with such a small box! Next time we get a package in the mail we're going to use the box to make a bigger cannon.

Flying cups!

It was also fun to shoot at targets from opposite sides at the same time

Plastic Bag Hot Air Balloon

We really wanted to try making our own hot air balloon from a plastic bag. There are a lot of different ways to do it, and tutorials. I thought this one looked most promising (the instructions are very detailed). There are 6 videos to watch. We almost, almost got our balloon to fly. It hovered for a moment. But it just wouldn't go all the way up. We tried it first with a dry-cleaning bag (it started to melt before getting very far up, though it did stand up) and then with a small trash can liner we got at church, but it must have still been too thick---or perhaps the folds on top needed to be smoothed out so they didn't get so hot (he shows this in one of the videos).

We would have tried again, but we had no more bags, no more candles, and no more time that day! But it was a really fun project, and not too difficult. The boys did all the measuring and taping/cutting of the straw frame, the foil, etc. by themselves, and I helped with attaching the candles to the foil. I read that you can use hot glue instead of melting the wax, and I think that would have worked better (the wax had a tendency to be unstable). There are other good troubleshooting suggestions on this main page also.

Candle platform

Measuring the bag

Attaching the "frame"

Ready to fly

We do have this on our list of things to do another time! I really think we can get it to work better, so next time I have to have something dry cleaned we'll give it another go!

We also might give one of these methods a try (there are several other tutorials like this one around), but because the heating apparatus is not attached, I'm not sure it would be as effective. Might be worth trying, though.

Fully inflated

Almost!

The Albuquerque Box

While we were looking up the history of Albuquerque's Balloon Fiesta, we learned about something really interesting called the "Albuquerque Box." It's a wind/weather pattern that happens because of Albuquerque's geographical position. Basically, for this pattern to occur, you need very dry air, a small/enclosed valley, and a place where daytime warms and nighttime cools are widely disparate.

I'm not an expert on this, but as I understand it, when these conditions are right, the cold nighttime air falls down the mountains/mesas to lower elevations. As the sun comes up and starts to warm the upper air, it creates wind between the air layers that makes a strong air current in one direction (south, in this case). As the cold air moves south and away from the enclosing "walls" of mountain, it warms and moves upward in elevation. Another air current then forms, moving the opposite direction, back toward the enclosed valley. The warmer air then cools again, falls, and joins the other current moving south.

You can see why balloonists would like this phenomenon: when it is present, they can take off from one location (the balloon fiesta park, e.g.), fly at low altitude south for a while, and then, when they wish to return, go up higher to catch the "return trip" wind current right back to where they started!  No chase vehicles necessary. :) Of course, the Albuquerque Box doesn't occur all the time, but it's more common in Fall when the Balloon Fiesta takes place, and when it does occur, it makes for great ballooning, apparently! Interesting, eh?

Hot Air Balloon Unit

Hot air balloons (and gas balloons) have a pretty fascinating history. I knew there would be lots of related scientific principles to learn, but I didn't know about the use of balloons as the first "air force" in several wars, notably the Civil War. The book Lincoln's Flying Spies (Gail Jarrow) was really interesting. It was too long for me to read the whole thing to the children, but I read it all myself, and then read excerpts to them, and summarized other parts, and we looked at the pictures.

Of course the highlight of the unit was getting to see the hot air balloons at the Balloon Fiesta in Albuquerque, but we also really enjoyed the Balloon Museum there at the end of the launch field. There were a lot of hands-on activities, some of which we skipped because of the crowds, and we also liked seeing several historic balloons---ones used for transatlantic flight attempts, etc. I feel like it's kind of sad that, because of all the advantages airplanes have over balloons, the impetus to make passenger airships, etc., kind of fizzled out. Not that I don't like airplanes---but there's something so majestic and beautiful about a balloon. I'd love to ride in one of those big zeppelins or airships! :)

I was also just thinking how nice it is to have a usable vocabulary about various subjects. I don't care about knowing all the fancy jargon that only experts use, but it's just satisfying to be able to say (and have the children say), "Look, now the hot air is going through the skirt into the envelope!" rather than "Look at that flap part directing the air into the balloon part!" Or, "He opened the parachute valve!" instead of "The top flap thing is opening!" It's not that big of a deal, but I just like being more accurate and effective in our speech. And I like hearing the children use those words even when they are just playing with each other.

Here's a good overview of how balloons work:

http://science.howstuffworks.com/transport/flight/modern/hot-air-balloon.htm/printable

Parts of a balloon:

http://www.chm.bris.ac.uk/webprojects2003/hetherington/final/Hot_air_balloon_parts.html

A coloring page---no educational value, but it was fun to color rainbow balloons

We watched several videos of hot air balloons and balloon flights:

This one was cool (amazing scenery!): http://www.youtube.com/watch?v=LSV9INvPvQA

This was also good:

http://www.youtube.com/watch?v=77Ej_Ayugxk&playnext=1&list=PL04A9F2900A881539&feature=results_video

And here is Daisy riding in the hot air balloon Abraham built for her! (that's my big exercise ball under the blanket on top) :)

Water Pressure

I don't have a lot of pictures, but understanding water pressure is essential to understanding how dams and water towers and pipe systems work, so we had a lot of discussion about it (and, peripherally, air pressure). Along with the bottle demonstration pictured above, the older boys were delighted to play this trick on Sam. We also used Sebby's straws (he got these for his birthday a couple years ago) to experiment with the ways that pipe thickness, distance, gravity, etc. affect water pressure.

They took their hole-y water bottles outside and pretended they were water towers (enterprising Abe, whose bottle worked fastest, was charging "money" for the others to fill their cups at his water tower)

We talked about clouds and rain and lightning on one of the days (just briefly; we will do a longer unit on weather sometime because there's lots more to cover!), and made these clouds in a bottle. We also loved making "lightning" with balloons and light bulbs (as described here and here). We did this demonstration in my closet and the kids LOVED it. They were all giggly and nervous there in the dark at first, not knowing what would happen, but after we made it work a few times, they could hardly be persuaded to stop! [note: We used a CFL and I thought it looked much more impressive with that than with his long fluorescent bulb in that second link, but I do really like his explanation of volts vs. amps and how fluorescent bulbs work. ]

A couple other good resources we used on water and air pressure:

http://thehappyscientist.com/science-experiment/feeling-pressure

http://www.asme.org/kb/news---articles/articles/k-12-grade/5-ways-to-demonstrate-air-pressure-to-children

http://thehappyscientist.com/science-video/cartesian-diver

http://www.history.com/shows/underwater-universe/videos/the-science-of-water-pressure#the-science-of-water-pressure

http://www.abc.net.au/spark/experiments/s1199904.htm