General Science: Case of the stolen skull

There were no two ways about it. I took her call 'cause I needed the money. The case was dirtier than a first grader's backpack and twice as heavy. The broad that hired me told me a couple a thugs took her skull, and I ain't talking about the one sitting on her shoulders neither. Seems she's into studying bones, and a couple of years backs some students gave her a horse skull they found. Now it was missing, and the only clues I had were four sets of prints and a pile of white powder.

Called in a favor with a buddy of mine downtown and he ran the prints and came up with a list of suspects with records so clean you could eat off of them. An English teacher, Devra Lehman, Asaf, the owner of the local toy store, the damsel in distress herself, Rebecca Perlin, and her husband, Danny Sadinoff. Each one had his own strange connection to a specific white powder: Devra to corn starch, Asaf to sugar, Danny to baking soda, and Rebecca to salt.

I let the boys in the lab take a crack at it. They tested the powder with more chemicals than you'd find in a package of Osem soup nuts. Then they looked at it under the microscope and checked if in solution it could conduct electricity. They compared the results to some similar cases they had a while back, and the answer was clear as day.

That science teacher must have thought I was some chump – turned out she was right. It was her and that other broad, the English teacher. One was in it for the thrill, the other for the spelling mistakes. Me, I had bigger fish to fry.

General Science: Chemistry in a bag

This week the kids carried out a really complicated lab. They mixed 4 different materials (calcium chloride, sodium bicarbonate, water, and phenol red) in a plastic bag. The materials that were liquids weren't added directly. Instead we first poured them into plastic cups, which themselves were carefully placed in the bag. Why all the extra steps? This allowed us to measure the mass of the whole business BEFORE and AFTER the chemical reaction took place. The kids were pretty surprised to find very little if any change. That's conservation of mass for ya!

As the materials combined the kids observed and recorded the many chemical changes that took place including: bubbles, color changes, and temperature changes. While all these changes were pretty cool, the fact we had combined so many different things at once made it tough to know what was really going on. Part 2 of the lab was breaking down the initial experiment into every possible combination of ingredients, carrying them out, and analyzing the results. By the end the kids new exactly which combo was responsible for each change.

General Science: Growing Crystals

This week we continued our investigations of solutions by making and examining crystals under the microscope. First we made saturated solutions of salt, copper sulfate, and borax. Then we placed a drop of each on a microscope slide, put them outside and waited for them to evaporate, and then used a microscope to look at the crystals that remained. We are also trying to grow some larger crystals. We'll see how they turn out next week...
One week later...
The good news is, Israel got a lot of rain this week. Great for growing crops, bad for growing crystals. We were hoping for our super saturated solutions (say that 5 times fast!) to evaporate, leaving behind beautiful crystals. Not likely to happen in the pouring rain. Next year we'll try this experiment in the late spring. In any case here's a picture of what you get when you SUCCESSFULLY grow large sugar crystals.

General Science: Which chip is the greasiest?

This week in science we asked the following questions: which brand of potato chip is the greasiest and more importantly, how can I be sure?

We went about answering them by carrying out 3 tests. The first 2 were a touch and a taste test in which the kids rated the chips on a scale from 1-5, with 5 being the greasiest. Then the kids were challenged to come up with a more quantitative test, one based on measurement. Some kids crushed equal amounts of each chip on a piece of graph paper and then compared the sizes of the different oil stains. Others compared the weight of the chips before and after crushing; the assumption being, the greasier the chip, the more oil lost in the act of being crushed on a piece of paper. Another test consisted of soaking different chips in water, removing them, and then comparing the amount of oil observed sitting on top of the water.

General Science: Solutions

This week we learned about solutions, that is liquid mixtures. In particular we wanted to know whether water temperature affects how well something dissolves. First the kids compared the time it takes to dissolve a couple drops of food coloring in different water temperatures. Then they tried to see how much sugar they could stir into solution, once again comparing different water temperatures. They concluded that hot water is much more effective at dissolving solutes (that's fancy-talk for stuff).

We also noted that the final volume of the sugar solution was surprisingly LESS than the sum of the initial water volume plus the sugar. Part of what happens when you dissolve something is that it breaks up into tinier pieces and more spaces open up within the molecules themselves.

General Science: White powders

This week we continued our exploration of physical and chemical properties by investigating 4 different white powders: sugar, salt, corn starch, and baking soda. The physical properties we investigated included: how each one looks under the microscope and how each one feels. As for chemical properties, we combined the powders with vinegar and iodine and recorded the results. Finally we looked at whether any of the powders conduct electricity when dissolved in water.

The kids now have a comprehensive data sheet on these substances and their physical and chemical properties. If by chance, they should come into contact with some unknown white powder, making an identification should be a piece of cake!

One never knows when these skills and/or data might come in handy...

General Science: Let your fingers do the talking

This week the kids learned about fingerprints, you know...dactyloscopy. They used graphite from their pencils and transparent tape to record each of their fingerprints. Then we looked at some common patterns and used these to classify them. Finally the kids produced a single "mystery" print which their partners were challenged to identify using the database of labeled fingerprints.

General Science: Iron nails in copper sulfate

While we're on the subject of chemical reactions here's a photo of an iron nail submerged in copper sulfate solution. As you can see, the color of the solution changes and in place of an iron nail you get a sandy solid that is copper. What actually happens is the iron displaces the copper and as the reaction goes to completion we are left with iron sulfate and copper.

General Science: It's a Gas!

For our experiment this week, we did an oldie but a goodie...what happens when you mix baking soda and vinegar?

Having some experience with making volcanoes or otherwise messing around in the kitchen, the kids guessed correctly that the combination would produce, in their words, "AN EXPLOSION!!!" (Aren't you glad this happens at my house and not yours?!)

This week we took it one step further to show that the combination of baking soda and vinegar produces a gas that can put out a fire. Passing a lit candle over baking soda had no effect on the flame. Same deal for the vinegar, but when you combine the two, and you get your EXPLOSION (i.e. bubbles), passing the candle over extinguishes the flame. Why does this happen? Mixing baking soda and vinegar is a chemical reaction, and as such, produces something new, carbon dioxide. That's what the bubbles are, and they have the property of putting out a fire and that's why they carbon dioxide in an actual fire extinguishers. Cool, huh!?

General Science: Iodine as indicator

This week the kids learned how to use an INDICATOR, a compound that changes color when it comes in contact with a particular substance. The kids were given around 10 different foods to test using iodine, an indicator that 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. Try chewing on a cracker for a few minutes (works best with unsalted ones), and you'll notice a sweet taste in your mouth that results from your saliva breaking down the starch into simple sugars.

General Science: Mixing Sulfur and Iron

This week we started learning some chemistry. Using a microscope and a magnet the kids explored the properties of 2 elements: sulfur and iron. Then they combined them and determined whether they had performed a physical change or a chemical change.

Here are some of the high points of their results:

iron: black, magnetic
sulfur: yellow, smelly, not magnetic
iron + sulfur: grayish yellow, smelly, BUT easily separated from each other with a magnet

Physical or chemical....you decide!

General Science: Going on Safari

This week the kids went on a different kind of safari. No big-game here, but instead hunted for microorganisms in a sample of pond water taken from Robert and Karen Clements' pond (thanks once again for your annual donation of pond scum!).

To get a sense of what we were looking for, we started off by watching a few short video clips of different microorganisms. Then the kids prepared their slides, making sure to get a sample of pond water that was nice and goopy. After hunting around a bit, the kids turned up some interesting single-celled organisms and even a water flea. What's cool about this little guy is that being transparent means you can WATCH its heart beat!

General Science: Ooblek, solid, liquid, or gas?

This week's challenge was to classify ooblek (roughly 2 parts cornstarch to one part water) as a solid, liquid, or gas. Pretty easy, right? Wrong! Ooblek belongs to an unusual class of liquids that become solid when subjected to sudden pressure or force. As it happens quicksand behaves remarkably similarly to ooblek, which comes in handy if you're an ooblek expert asked to consult on the best way to escape from quicksand. To thrash or not to thrash? The kids submerged action figures and plastic animals in the ooblek and compared the reults of rescuing them using quick movements versus slow movements. Their recommendation: Move slowly and don't panic. Thrashing around simply causes the ooblek (or quicksand) to solidify, making it even harder to get free.

General Science: The Right Stuff

This week the kids were charged with designing a spacesuit that could withstand the intensely high temperatures one might find on Venus. Lacking the funding to actually travel to Venus and not wanting to violate the Helsinki Declaration,* we used ice-pops instead of people and hot water instead of Venus. The kids made spacesuits using one of three available materials: tin foil, wax paper, and bubble wrap. Once outfitted with their spacesuits, each ice pop was submerged in a pot of boiling water for one minute. For comparison we also had a control ice pop, meaning an ice pop with no space suit. After a minute the kids opened up each ice-pop and measured how much of it had melted by pouring the liquid into a graduated cylinder. Of the 3 materials, bubble wrap was the best insulator.

*ethical principles for research on human subjects