Friday, June 24, 2011

General Science and Physics: Dry Ice

Dry ice is unlike the ice we know and love. It's frozen carbon dioxide, and it's called "dry" because it passes from the solid phase directly into the gas phase, skipping the liquid phase entirely, resulting in some AWESOMELY weird and funky behaviors! It's CRAZY-cold, so cold in fact, we only handled the dry ice with a towel or tweezers....NEVER with our bare hands!

We demonstrated its COOLNESS in the following ways...
  • compared "dry ice" to regular "wet ice"
  • produced a lot of spooky fog.
  • "poured" carbon dioxide gas into a cup on a scale and noted that it weighed more than an equal volume of air.
  • used carbon dioxide gas as a fire extinguisher (Don't panic, the fire was a single lit candle).
  • made long-lasting carbon dioxide bubbles by adding dry ice to soap solution.
  • made the dry ice "squeal" and vibrate after pressing it with a metal spoon.
  • inflated a balloon by putting a piece of dry ice inside and then tying off the open end.
The COOLEST thing we did was toasting a fantastic year of science with home-brewed soda.
Here's the recipe:
1. Pour juice into a pitcher
2. Add a block of dry ice
3. Enjoy the show as you down your cold, carbonated fruit-flavored soda!

Wednesday, June 22, 2011

Biology: Results are in!

The results are in! With the help of some vanilla ice cream and sprinkles the kids reviewed their results from the Science Fair, and here's what they found:
  • Vanilla is detected faster than other flavors.
  • Seeing red isn't just an expression. Our scientists found that staring at red raises your heart rate more than yellow or blue.
  • Doing exercise decreases the amount of time you can blow bubbles using one breath.
  • Listening to rock music was associated with the slowest relflexes.
Of course the results were only half the story. We also discussed sources of error and ideas for next time.

Monday, June 13, 2011

Science Fair

General Science:
Market Research Projects.Which ______ is the ______est?

In these projects the kids were challenged to compare everyday objects through the lens of scientific evaluation. To determine which object was the best for a particular category the kids had to define best in some way that could be measured and then set up conditions that allowed for a fair competition. This is the method used by all scientists regardless of their questions.

Physics: Inventors Workshop

Over the past few weeks the kids have attempted to design and build an invention that contains a lever. We agreed up front that it was unlikely that any of our inventions would succeed in the traditional sense of the word. After all, most inventors spend thousands of hours imagining, designing, building, failing, and restarting the process again and again. When you look at these projects, you should see them as a sort of diary of the kids dreams and their initial attempts to actualize them. Trial and error plays a role in the creation of every great invention. Here is a window into this process.

Biology: Human Body Projects thanks for volunteering

Working with people is never easy. Working with human subjects even less so. Part of what we discovered this year in biology is the complexity and lack of predictability you get with all living things. Whether its microscopic organisms in pond water or human size ones in my backyard, bottom line is it takes a lot of patience, planning, and careful observation to design and carry out an experiment with human subjects. The biology kids first did their experiments on each other. After analyzing their results they modified their experiments to arrive at what you see here today.

Making ice cream with salt without making salty ice cream!

This week we did a pretty COOL trick....we made ice cream, without a freezer, using our own DIY ice cream machine. How did we do it and what does it have to do with science?

The kids poured the ice cream ingredients (milk, vanilla, and sugar) into a small plastic bag. Then they placed this bag into a larger bag filled with a lot of ice and a lot of salt. The whole business was then wrapped in a towel and then shaken until the milk mixture solidified. The rock salt caused the ice to melt quickly and reach a sub-zero temperature, so that the resulting freezing salt water could quickly absorb heat from the milk mixture, giving you yummy, delicious ice cream or at the very least, a super-cool milk shake.

Here's the procedure in case anyone wants to try it at home.

1. Pour ¼ cup of milk into a sandwich-size zip lock bag.
2. Add 1 teaspoon of sugar and a couple drops of vanilla extract.
3. Close the bag carefully, while getting rid of the extra air.
4. Mush the bag around to mix the contents.
5. Place this bag in another sandwich zip lock bag, remove the extra air, and seal.
6. Fill a 1-gallon zip lock bag with ice and a half a cup of rock salt.
7. Place the double bagged milk mixture inside the larger bag, squeeze out the extra air, and seal.
8. Wrap each bag in a towel and mix, shake, and churn until the inner bag's contents freeze.


* Make sure all bags are closed, especially before you start shaking up the bag of ice and salt.
* Double-bagging the milk mixture is important, to help reduce the odds of salt penetrating the bag and getting into the ice cream (yuck!).
* Err on the side of too much ice and too much salt.
* Try to keep the milk mixture bag in the middle of the ice, and especially in the middle of the melted salt water.
* See what happens if you add different flavors like chocolate syrup or lemon juice.