This should have been a big success...

Jr. scientist E is obsessed with the moon. Every time my computer is out she asks to look at the pictures of the moon in our telescope gallery and she loves looking at the moon whenever it's out. So I've been excitedly waiting for the moon to be visible at a time when she'd be awake so we could look at it through the telescope. Tonight was finally the night. I set up the telescope, attached the camera so she could look at the camera screen instead of the much-more-difficult eye lens, and waited for the excitement. She was completely uninterested. I guess for a two-year-old the concept of looking down at a screen to see something up in the sky didn't make sense.

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.

Messy experiments

We made a couple of bubbly chemical reactions today. Jr. scientist A's prediction: "It's gonna be messy." For our first reaction, we mixed hydrogen peroxide and active dry yeast. This made big bubbles (left picture) that raised up in a high column before the column eventually fell over. For our second reaction, we mixed baking soda and vinegar and got much smaller bubbles that quickly ran over the edge of the container (right picture). Jr. scientist A. liked these experiments a lot.

Making things sink on command

Today we played with surface tension. We dropped a loop of yarn onto a bowl of water and it floated. We then added some drops of dish detergent, breaking the surface tension, and the yarn sank to the bottom. We repeated the experiment with a few other objects. A twisty-tie floated until we added the detergent. A paperclip sank right away - oops too heavy. Paper floated, even after we added detergent, but sank to the bottom when we pushed it under water. A cork floated no matter what we did. Its buoyancy amused jr. scientist A.

Sun bleaching in the rainy season

We did some more sun bleaching - this time making sure everything was firmly attached to prevent the cats from interfering. It ended up raining and raining and raining for days in a row, making it take more days than usual. In the end it turned out pretty well. Jr. scientist A. wanted me to cut out the rectangle to carry around and then was surprised that, without the surrounding bleached out paper, it just looked like an ordinary sheet of construction paper.

Clanking coin

We tried an experiment from 365 More Simple Science Experiments with Everyday Materials. The idea is that if you put a bottle in the freezer, it fills with cold air. When you take the bottle out of the freezer, the air inside the bottle warms up and therefore expands. If you block the way out for the expanded air, it will cause pressure to build up behind the blockage.

We first tried with a plastic bottle, putting it in the freezer for 5 minutes. We took it out, put a wet quarter over the bottle opening, and waited. Unfortunately nothing happened. We tried a glass bottle with a smaller opening, thinking the quarter wasn't fully blocking the mouth (or that the sound of a quarter on plastic wasn't very noticeable). The quarter did lift up and clank back down as pressure built up and was released in the warming bottle . However, there was a long time between clanks. We tried cooling the bottle overnight to make sure the air inside was very condensed. This worked well. We got lots of clanking, one after the other. Jr. scientist A. got quite a kick out of it.

Hydrophobic experiment, take 2

Our last hydrophobic experiment was less than successful, although we did learn that you can't dye olive oil with food coloring. Part of the problem was one of scale - it was too difficult to see the color difference with just a small layer of oil. This time we filled a small water bottle half full with water dyed red with food coloring. We then filled the other half with olive oil and sealed the bottle. We then shook up the bottle, making the liquid one uniform color. Nearly instantly the oil, being hydrophobic, started to separate out. We checked on the bottle every 1-2 minutes, watching the water and oil slowly separate. Within about 10 minutes, the two were almost completely separated, with a yellow liquid (oil) section and a red liquid (water) section.

What I liked about this experiment:

It allows a lot of jr. scientist participating - after the raw materials are in the bottle and the bottle is sealed, they can do the rest of the experiment themselves

It's infinitely resettable - at any point the bottle can be shaken and the experiment restarted

It's robust

It works quickly

It's fun

Tin can phones

We had some empty giant coffee creamer plastic containers so we decided to make some "tin can" phones. We had made some before using paper plates, string, and popsicle sticks (wrapping the string around a popsicle stick up against the plate), with limited success. The coffee creamer containers worked much better, probably because they captured sound better and added their own funny-sounding resonance. We also figured out that we could use one of the containers as an amplifier so when we strummed the string between the two "phones" we could hear a clear note come out of each container - a good example of how the string was transporting vibration and the containers were turning those vibrations into sound (o.k., technically the ear was turning them into sound and the containers were just amplifying and modifying the vibrations). Overall I'd say it was a fun experiment that worked well.

Sun-bleaching

We're starting to do some experiments using the sun. The big downside is that these tend to take awhile so they're more set-it-and-forget-it types of experiments. Our first sun experiment is sun-bleaching. Since the sun will bleach color out of construction paper (or just about anything else), we set up a sheet of bright red construction paper in a window that gets strong sunlight and put a few objects on it - the idea being that the sun will bleach all of the paper except what is under the objects and we'll end up with permanent "shadows" of the objects.

Our first attempt was thwarted by our cats, who clearly aren't big fans of science (they often try to chew on the materials for our science projects) who knocked all the objects into different places on the paper each day, giving us multiple and ill-defined "shadows." Still very exciting to see that the experiment can work! We're now clipping a key to the paper, which I hope will prevent the cats from causing more mischief.

Next up: sun dials and pin hole (construction paper) cameras.