Homemade compass

We decided to build our own compass to help orient us for our stargazing. We magnetized a paperclip using our dangerously powerful- magnet (rubbing the paperclip across the magnet many times). We filled a container with water and put our now magnetized paperclip on a piece of cork in the water. The paperclip and cork slowly rotated until it was oriented north-south. We spun the cork around multiple times and it kept re-orienting itself. Pretty cool to see this invisible force at work (although next time I'll use a round piece of cork so it doesn't get stuck on the edge of the container without being able to turn). Jr. Scientist A liked the experiment, but I have a sense that the underlying concept of the earth having a magnetic field was a little too advanced.

Why does yeast make dough rise

Jr. scientist A often asks why we add different ingredients when we cook and one of the common ingredients we use (since we make a lot of pizzas) is yeast. I decided a while back to try to give a better answer than my standard, "yeast makes dough get bigger" response. I knew that there was carbon dioxide being released that formed little pockets in the dough, thus expanding it, so I thought we could do an experiment where we use yeast to blow up a balloon. Originally I put some yeast and water in a bottle and covered the mouth with a balloon. We checked on our experiment the next morning to find a still deflated balloon. I tabled the experiment for a while and was poking around online and found I was missing a key ingredient - sugar. We re-did the experiment with two bottles. The smaller bottle had yeast and water and the bigger one had yeast, water, and sugar. By the next morning the bottle with sugar had a nicely bulbous balloon sitting on top of it. Thanks to some laziness, we discovered that the bottle without sugar did eventually make enough carbon dioxide to partially inflate the balloon, but it took a few days to happen.

Levitating ball

This is one of those experiments that I've seen in a number of books and kept passing up because it seemed like one of those experiments that looks like they should work but never do. The idea is that you use a hairdryer to "float" a light ball in the air. It works using Bernoulli's principle (the same principle behind airplane flight) - the fast air moving around the ball creates an area of low pressure, effectively acting to hold the ball in a tunnel. We were flipping through one of our books and Jr. scientist A found that experiment and asked to do it. I reluctantly got out the hairdryer, pointed it up and placed it on cool air, and gently placed the ball in the air stream. I was more than a little surprised to see the ball just float there on a cushion of air. Then Jr. scientist E did the next logical experiment - she nudged the ball. It moved a little and then moved back on its own to the center of the air stream like it was attached to a spring. That really got her excited. We all had a lot of fun with this experiment.

Exploring the lunar surface

Since jr scientist A has quite an interest in outer space, we decided to investigate why the moon looks like it does. I ran across this experiment in Pop Bottle Science (yes, I know, this has nothing to do with pop bottles). We looked at some pictures of the moon with all its craters and I asked jr. scientist A where he thought all those bumps came from. He didn't have any idea so we got out a container and some flour and made a mock lunar surface. Then I rolled a piece of play-dough into a little ball and threw it into the flour resulting in a mock crater in our mock lunar surface. Jr. scientist A had lots of fun making craters and it seemed to really make sense to him. It was a great way to explain an otherwise difficult to conceptualize idea (I wish I could take credit for coming up with the experiment!)

Electromagnets

After previous unsuccessful attempts to make an electromagnet (and my clear deficiency in electrical experiments), we turned to my first science teacher, Dr. A, for a little help. After finding the right type of wire (who knew there's a lightly insulated wire labeled specifically for making electromagnets - well I didn't, but thankfully Dr. A did!), we quickly had our electromagnet up and running, complete with a light switch that turned the magnet on and off. Jr. Scientist A had fun flipping the switch on, picking up metal objects like paperclips and silverware, and then flipping the switch off and watching them drop. Some paperclips did get temporarily magnetized, making the dropping effect a little less dramatic and the concept a little less clear, but it was still quite a success.

Playing (safely) with electricity

We got Jr. scientist A a snap circuit kit where we can put together different electrical experiments (the different parts of the circuits snap onto a board like Legos). He had lots of fun trying to put every piece of the kit on the board but I was eventually able to convince him to separate out the pieces needed for the "flying saucer" experiment (the little island of circuits in the middle of the board). After a little fiddling we launched the flying saucer by putting it on the motor, getting it going fast, and then cutting the power. The little disk flew up in the sky - it was pretty cool. Bedtime got pushed back quite a bit as we played with the new toy.

Baking soda and vinegar reaction without the vinegar

We found this reaction by accident. We decided to try to make baking soda crystals. Just like we've done when making salt crystals, we started with dangerously hot water so that we could dissolve a lot of baking soda into the water. To our surprise, when we dropped the first spoonful of baking soda into the water, it fizzed up as if there was vinegar in the solution. Thinking that I had grabbed a container that had a little vinegar residue in it, we marched on with our crystal experiment (standing a little farther back). Every time we added baking soda, we got another fizzy reaction, long past the point where any vinegar residue would have been used up in the reaction. It turns out that mixing baking soda into hot water does create carbon dioxide, just like when mixing vinegar and baking soda. Granted this was (unintentionally) not the safest experiment, but it's always fun to find a new fizzy reaction. Of course, Jr. scientist A had quite a lot of fun repeating this one.

Noisy noisy balloon

I found a fun sound experiment where you drop a nut (the metal type) into a balloon and inflate the balloon. When you shake the balloon you can get the nut to circle around inside, making a neat whirring sound (thanks to the repeated pattern of the edges). Jr scientists A and E had fun playing with this one. Making the sound is clearly easy enough for a baby - Jr scientist E had no trouble making it go. The only downside is that the nut starts to make tiny tears in the balloon after a few minutes, resulting in an increasingly small (and less fun) balloon. Maybe we should start buying balloons in bulk.

The curious case of gak

We made a batch of gak - mixing cornstarch and water to make something between a liquid and a solid. Jr. scientist A had fun playing with it and making quite a mess. Jr. scientist E's reaction was very interesting. I dipped her hand into the gak slowly (making the gak act like a liquid) and then dipped her hand into the gak quickly (making it act more like a solid). She got a very curious look on her face when the previously liquid gak suddenly seemed solid. I think it dawned on her that something surprising was going on. It was pretty neat to see.

Anti-gravity pepper

I didn't expect this to be such a cool effect. We put some pepper on a sheet of paper and then built up an electrostatic charge on a balloon by rubbing it against our hair (Jr. scientist A thought that was pretty funny). As we brought the balloon close to the pepper, the pepper became positively charged and started flying up off the paper and onto the balloon. As we held the balloon in place, more pepper kept flying up (and down) for a few seconds. It was so neat we kept repeating the experiment, trying to build up an electrostatic charge in different objects like plastic spoons (worked well) and cups (not so well). Jr scientist A and the senior lab members watched in amazement.

Hidden bubbles

We found this effect quite by accident. One of Jr. scientist A's new favorite things to do is to mix various ingredients together to see what happens - I think we have a budding chemist! We were adding things to red cabbage-dyed water (a pH indicator). As expected, when we added baking soda, the mixture turned blue, and adding vinegar to the same mixture caused it to bubble and then turn red. What caught us by surprise was that we next added salt and the mixture bubbled again. I had never heard of salt causing a chemical reaction resulting in bubbles, so we did some more investigating. Adding more salt turned the mixture from red (acidic) to purple, as would happen when you added a base, making us think that salt was a base (it's actually neutral). We tried combining vinegar and salt in another cup and got a rather unexciting cup of salty vinegar with no bubbles. After some google-ing, we found out that the salt wasn't actually creating bubbles, it was releasing the carbon dioxide bubbles trapped in our mixture after the baking soda and vinegar reaction. We decided to try adding salt to soda and got instant bubbles again. We even were able to create a little soda fountain (nowhere near as big as the mentos and diet coke reaction, but still cool). Jr scientists A and E both got quite a kick out of this accidental experiment, and I think it will become a new regular experiment.

Rafting

As a first step towards making an air- or rubber band-powered boat, we took some small pieces of corkboard and turned them into rafts (that is, we put them in a pool). Our brave gingerbread man once again sailed out to sea as Jr. scientist A made waves to get the raft to go to different ends of the pool. As for Jr. scientist E, she just giggled every time the raft sailed by her. An unexpectedly fun first step towards a bigger goal.

Water-crayons

Jr. scientist A wanted to do an experiment with swishing water in a bottle. We started out trying to make a tornado in a bottle where you tape two bottle caps together facing opposite directions and poke a hole through them both. When you attach the caps to two bottles (one with water) and swirl the bottles, you're supposed to get what looks like a tornado. Unfortunately, our tape didn't hold and we were left with two separate bottles with holes in the cap. So what do you do with bottles with holes in the cap? Make water-crayons of course! When you turn the bottles upside-down and squeeze, you get a steady stream of water that you can use to "draw" with. We had a lot of fun drawing shapes, people, animals, or just scribbling (Jr. scientist A also had fun "drawing" on my feet every chance he got!). What a fun accidental experiment.

Changing colors

Red cabbage juice is pretty cool. It changes color based on the pH of its environment. We got some dehydrated red cabbage juice powder in a science kit and decided to try it out. We mixed some of the powder and water in two cups, making some nice purple mixtures. We took our favorite acid and base (vinegar and baking soda, respectively) and added the baking soda to one cup and the vinegar to the other, getting bright blue and red mixtures (shown in the picture). Jr. scientist E was not impressed by the color changes, but Jr. scientist A really got into it. He immediately came up with a list of items to add to the mixture. We added baking soda to the vinegar mix, turning it back to purple (after the bubbles subsided). At Jr. scientist A's insistence, we added lemon juice, orange juice, flour, coffee, nuts, and various other things we had on hand - not a pretty mixture in the end but quite a crowd-pleaser!

Separating colors

This experiment came from friend-of-the-lab Sandy. The goal of the experiment was to show that black is made from a mixture of colors. We put a long strip of paper in a bottle so that the paper went from the bottom of the bottle, up and out the top, and down to the table top. We filled the bottle part way with water and made a thick black line on the paper above the water level using a permanent marker. By the morning, our thick black line had turned into a smearing of colors. Although Jr scientist A would clearly have liked the black to separate before our eyes, the experiment clearly sparked his imagination and he's now asking to see what other colors are made of.

Peering into the microscopic world

Jr. scientist A just got a microscope (thanks Arthi and Glenn!), so we've been exploring the microscopic world. He instantly noticed that there was something very telescope-y about this new device ("it has a focus knob!"). As with the telescope, I wasn't sure how much he would be able to see through the lens, so we played the "what do you see" game. We looked at some string (top right photo), which he described as "branches" - a pretty good description. We also looked at colored sugar (bottom right photo), paper, grass, salt, sandpaper, and a few other things. Jr. scientist A had a lot of fun, but this was another one of those experiments where he had to compete with the adults for a turn!

Paper boats

After some attempts to make floating canoes with paper and glue, which inevitably sunk when the glue dissolved, friend of the lab Arthi provided us with an origami paper boat. We sailed (and sank) our boat in the bathroom sink, much to the delight of jr scientists A and E. The experiment also turned into a surface tension experiment when our paperclip passenger stayed afloat after our boat sank. Remembering back to an old experiment, we added some dish soap and watched the paperclip plummet.

Frozen boat

Inspired by an episode of MythBusters, we made a boat out of wet scraps of paper frozen together. We sandwiched the wet paper between two tupperware containers and put it all in the freezer. After it was frozen, we popped out the boat and set it to sail on the high seas of the bathroom sink with some brave gingerbread men, much to Jr. scientist A's delight. After a few minutes, the boat thawed and came apart. We put it back between the tupperware containers to re-freeze and sail again another day.

High flying fun

I swear there was a time when I could make paper airplanes that flew, but that time has clearly passed. So I got a book on making paper airplanes (recommended by friend of the lab Arthi). We were able to make a bunch of really cool airplanes (some of which actually took decent flights). Although I got this book for Jr. scientist A, I was surprised at how much fun the younger Jr scientist E had watching the airplanes fly by. She eventually started toddling over to where they fell and bringing them back for another flight. We had a lot of fun seeing how different designs and different modifications resulted in different flight patterns (I have to confess that I started making two of each design because I wanted more turns!). At some point, Jr. scientist A must have decided that the planes were flying because they were made of paper and insisted on trying to fly an (unmodified) paper bag. This isn't the first time that he's gone from observer/participant to actively guiding experiments in new directions, and I have to say I'm a bit proud of that!

Fizzy colors

Looking for a good experiment for Jr. scientist E, at my wife's suggestion I went back to an old fizzy standard - mixing baking soda and vinegar. To make it more interesting, I put down a drop of red food coloring and a drop of blue food coloring, with the baking soda and vinegar in the middle. As the fizzy mess spread, it took up the food coloring. Jr. scientist E just stared intently at the bubbly concoction (I think with interest!), getting transfixed each time I added more baking soda or vinegar to restart the fizzing.