Making paper

For this experiment we turned paper into... paper. We started with some old newspaper and magazine pages and tore it into shreds (Jr. scientist A. is so good at doing that with paper he's not supposed to tear, but seemed unwilling to do it when he had permission!). We put the paper and some hot water in a blender, let it sit for 20 minutes, and then blended it into a watery mixture. We poured the mixture over a silk screen that was placed over a bin lined with a garbage bag. We then added leaves and a pressed flower we had collected on walks and pressed out some of the water. We let it sit in the sun, periodically pressing out more water. We eventually learned to put wax paper on top of the mixture before we pressed out the water after we kept pulling off parts of the "paper." After a day, it had dried and we carefully peeled it off the screen. We were left with (somewhat delicate) paper that had some of the leaf patterns pushed into the back side. A fun, albeit slow project.

Stalagmites and stalactites

After visiting a cave exhibit at the zoo, we decided to try to make our own stalagmites and stalactites. We dissolved as much Epsom salt as we could into hot water and divided it into 4 empty baby food jars. We added different food color to each jar and then hung strings between them - some wool and some cotton. Each string was weighted down on either end with a paperclip. The idea was that the water/salt mixture would go along the strings and drop down near the middle where the strings dipped a little. Over time, this should cause some crystals to grow down from the string where the water was dripping from and grow up from the container where the water dripped to. Unfortunately, the liquid never made it up any of the strings, so we never got any stalagmites and stalactites. However, crystals started growing both around the rim of the jars and on the outside sides, and even around the outside base of the jars! We didn't expect that - and it saved our experiment from complete disaster.

Rocket balloon

This should work. Inflate a balloon, attach it to a straw with a tethered string running through it, and when you let the air go out of the balloon, the "rocket" should be propelled along the string. But despite various different rocket "designs," we haven't been able to get this to work. We've tried taping a big balloon directly to the straw with packing tape (the balloon may move a little along the rope but not very far - and re-inflating the balloon tends to make it pop because of the tape stuck to it), attaching a paper towel tube to the straw and sticking a long thin balloon into it (the rocket doesn't move at all), and taping a long skinny balloon to the bottom of the paper towel tube (again, basically no movement). Maybe it's not enough force, maybe the pressure is not being well directed. All I know is we can't seem to get this experiment to work. How frustrating!

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.

Musical bottles

Today we turned bottles into whistles (blowing air across the top to make a note - a bit beyond the abilities of jr. scientist A). We added and removed water from a bottle to see how it changed the note we heard. As we added water (i.e., less air in the bottle) we got higher notes and as we took away water we got lower notes. We then tried to figure out if other things besides how much air was in the bottle affected the note we got. We took three different types of bottles (a wine bottle, a glass coke bottle, and a plastic water bottle). We filled both the wine bottle and the water bottle all the way with colored water. We then poured enough water out of the wine bottle to fill the coke bottle, emptying out the coke bottle afterwards. We did the same thing with the water bottle. This way, all three bottles had approximately the same volume of air in them. We then made a note on each bottle and got three very different notes! I think I was more excited about this than my son - it seemed to be a bit too advanced for a toddler - but I thought it was really cool. Clearly the shape/size of the bottle and the volume of air in the bottle both matter.

Growing crystals

We tried to make crystals by dissolving Epsom salt in water. We heated water up in the microwave (so we could dissolve the salt at the table in plain view). After we dissolved as much salt as we could (with some undissolved salt sitting at the bottom of the cup) we microwaved it again. This dissolved the remaining salt and let us mix more in. We repeated this a couple times, added food coloring, and poured a shallow layer of the solution into a tupperware container. After letting it sit a couple days so the water could evaporate, we were left with some rather unimpressive crystals. It was essentially a somewhat sparkly layer of material. We'll have to work on making better looking crystals.

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.

Hydrophobic experiment

Trying to demonstrate what it means for something to be hydrophobic, we mixed together water and oil in a small (2 Tbs) measuring cup. The result was a rather unimpressive separated mixture with one layer clear and the other label an unimpressively different slight yellow. We added some red food color to the mixture - still not an impressive difference between the two layers. We tried to dye the oil a different color and learned that whatever the food coloring is made of, it's either water of hydrophilic - at best, we could get little dots of color in the oil. We'll have to work on this one.

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.

Invisible forces

Materials
clear tupperware
pen
string
paper clip
magnet

Results
Success

Working theory
Since magnetic fields can't be seen, if we tether a paper clip and put something between the paper clip and the magnet, the magnetic field should be more apparent.

Experiment
We tied a paper clip on a string and tied the other end to the middle of a pen. We put the pen across the top of a clear tupperware with the paper clip just touching the bottom of the tupperware. We moved a magnet around under the tupperware, dragging the paper clip around through the tupperware without it getting "stuck" to the magnet.

Baking soda and vinegar rocket

Materials
soda bottle
scissors
baking soda
vinegar

Results
Perplexing

Working theory
Combining baking soda and vinegar creates a large amount of carbon dioxide gas, causing the mixture to expand and bubble out of the container. If we can direct that pressure downward, we should be able to propel the container upwards.

Experiment
We took an empty soda bottle and used a scissors to poke a hole in the lid. We put a good amount of vinegar into the bottle and filled the cap with baking soda. After our safety goggles were on we put the cap on the bottle and shook it up (with a finger over the hole). We placed the bottle on the ground, cap side down and stood back. Although the bottle became very pressurized and a bubbly stream came shooting out of the hole, we didn't get any lift. We think that either pressure was going out of the edge of the cap, near the threads (aimed upwards) or the cap wasn't flush against the ground, causing the pressure to go out at an angle.

Paper clip trains

Materials
paper clips
refrigerator magnet

Results
Success

Working theory
Ferromagnetic items (generally those with iron) can be magnetized. By rubbing a magnet across a ferromagnetic item like a paper clip, you can temporarily magnetize the item.

Experiment
We repeatedly rubbed a refrigerator magnet along a paper clip (always in the same direction - not sure if that matters). We were then able to use the magnetized paper clip to pick up another paper clip. By rubbing the magnet along multiple paper clips, we were able to make a series of magnetized paper clips. Placing them head to tail in a line we were then able to pull the whole train of paper clips by pulling the first one. We also magnetized other objects like certain keys, finding out that we could only magnetize objects that the refrigerator magnet would stick to (i.e. those that are ferromagnetic).

Rubber band guitar

Materials
Kleenex box
rubber bands
pens

Results
Success

Working theory

Sound results from periodic (i.e. regular) vibrations. Changing the length, thickness, or tautness of a rubber band should change how it vibrates and what pitch it produces.

Experiment

We started by placing different sized rubber bands around an empty Kleenex box, strumming the part of the rubber band that was over the opening of the box (where the Kleenex come out). This created a muted and muddy sound. Thinking the rubber band was up against too much of the box, preventing sustained vibrations, we moved two pens under the rubber bands and strummed in between them, making a nice note. By changing the distance between the pens (lengthening or shortening the part of the rubber band that vibrated), we were able to systematically change the pitch we got.