General Science: Indicators for acids and bases

This week we learned about acids and bases and two types of indicators you can use to identify them. We began by using red and blue litmus paper to test different household liquids. We were then able to classify them as acids, bases, or neutral. However while litmus paper is useful, it doesn't tell you anything about how strong or weak a base or acid is. So, for example, while baking soda and bleach, the two bases we encountered, score the same on a litmus test, baking soda tastes mildly bitter whereas tasting bleach will land you in the hospital (hypothetically speaking, of course!). We observed that in order to appreciate this without landing in the hospital, pH paper comes in real handy.

General Science: Dry Ice

We started off the session by discussing what makes dry ice so COOL.

While it looks like regular water ice, it is actually frozen carbon dioxide. It is genuinely cooler than regular ice. That's why we ONLY handled the dry ice with tweezers. Possibly the coolest part is how it sublimes, meaning it changes directly from solid into a gas, skipping the liquid phase.

Then we demonstrated its coolness in the following ways....

• froze cooked pasta and flowers by dropping them in acetone with dry ice. (Acetone is good thermal conductor, so it gets really really cold.)

• 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).

• measured temperature changes in water after adding dry ice.

• made the dry ice "squeal" and vibrate after pressing it with a metal spoon.

• inflated a latex glove by putting a piece of dry ice inside and then tying off the open end.

• produced a loud popping sound by placing a piece of dry ice in a small plastic container and then closing it.

Physics: Dry Ice

We started off the session by discussing what makes dry ice so COOL.

While it looks like regular water ice, it is actually frozen carbon dioxide. It is genuinely cooler than regular ice. That's why we ONLY handled the dry ice with tweezers. Possibly the coolest part is how it sublimes, meaning it changes directly from solid into a gas, skipping the liquid phase.

Then we demonstrated its coolness in the following ways....

• froze cooked pasta and flowers by dropping them in acetone with dry ice. (Acetone is good thermal conductor, so it gets really really cold.)

• 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).

• measured temperature changes in water after adding dry ice.

• made the dry ice "squeal" and vibrate after pressing it with a metal spoon.

• inflated a latex glove by putting a piece of dry ice inside and then tying off the open end.

• produced a loud popping sound by placing a piece of dry ice in a small plastic container and then closing it.

Physics: Friction

This week we revisited a concept we discussed earlier this year, FRICTION. The kids built inclined plane devices (that's fancy talk for a ramp and a protractor), and they measured the minimum angle necessary for a stationary 10 agurot piece to begin to move. The idea being, the steeper the angle necessary to get the coin moving, the greater the friction between the material and the coin. We compared wood, plastic cutting boards, styrofoam, binders, and cardboard.

Now before you start with your "what possible applications and practical value can this highly theoretical and esoteric research have for me in my every day life..." you should know that following this highly controlled experiment, the kids designed a related experiment they will carry out next week in the field: Sitting on which material makes YOU to go down the slide the fastest?

Stay tuned.

General Science: The Case of the Stolen Handouts

This week we were supposed to do a fascinating investigation, Salt: What makes it taste so darn good? As usual, I placed the handouts on the table, and then left for a few minutes to gather some supplies. When the kids arrived, my whiteboard was lying on what I thought was the pile, but when I lifted it, I was quite shocked to find no paper, but a PILE OF MYSTERIOUS WHITE POWDER!!!

While the kids were checking outside for clues, I quickly dusted for fingerprints, messengered the fingerprints over to the police station, and after a lightning-fast search through their databases, they faxed me a list of suspects (further proof Raanana is in fact Israel's most efficiently-run city).

Suspects:
1) Danny Sadinoff, a real meat-and-potatoes guy who likes his gravy so much (and so thick), that he is often seen carrying a bag of corn starch. When questioned he admitted that he needed some paper to block the sun out of his office since there are no curtains.

2) Chen Sadinoff, aka babyface likes nothin' better than Cheerios with a generous sprinkling of sugar. She's known to be quite mischievous, stealing people's homework and other important documents only to scribble on them in some top secret language known only to her and her evil associates.

3) Asaf, owner of the popular Yaar Kasum stationery store: Asaf could not be found when we came to question him, but a woman who works there mentioned that she has heard him complain about my having cut back on the copies I make there. Also suspicious were the packets of baking soda sitting on the counter.

4)Me...Look, it's not surprising that MY fingerprints were found. After all, it is my kitchen. Still, some of the more cynical members of the chug had the nerve to suggest that I had planned the whole thing. Pretty ridiculous, I know.

Luckily our amateur detectives had some previous experience identifying white powders. With the help of iodine, vinegar, a microscope, and an electrical circuit run through water, they were able to identify the powder and ID the bad guys.

Turns out the powder was a mixture: salt and corn starch suggesting that it wasn't one perp but two. And, if it weren't for you meddling kids, Danny and I would have gotten away with it!

Physics: All the world is a narrow bridge

This week was the 3rd and final week in our unit on bridges. After learning about the different types of bridges as well as various bridge-building principles, the kids were challenged to build a bridge that spans 42 cm that could hold the maximum weight.

Each kid/team was given 25 straws, masking tape, and 1 m of fishing string, and about an hour to build their dream bridge. There was a quite a range of diversity including beam bridges, suspension bridges, and truss bridges. There wasn't too much in the way of arch bridges given the limitations of straws as a building material. However, many kidsused what they learned about buttresses to strengthen their bridges and columns.

Personally, I think the kids just like saying "buttress."

General Science: Iodine as indicator

This week the kids learned how to use an INDICATOR, a compound that will change color when it comes in contact with a particular substance. Without too much background on what starches are, the kids were given around 10 different foods to test using iodine, a compound which changes from orange to black on contact with starch. As they made their way through the food samples (testing them, not eating them), they were able to refine guesses about what starches have in common. Finally, we concluded that starches come from plants and are how plants store simple sugars.

Afterward we discussed how simple sugars are connected by chemical bonds to make complex sugars and conversely, how the chemical bonds within complex sugars are broken to produce simple sugars. The kids chewed on that for a few minutes...literally! I gave each one a cracker, and they observed how after a few minutes of chewing, they could taste the sugar that resulted from their saliva breaking down the starch.