Thursday, March 18, 2010

General Science: The Case of the Stolen Handouts

There were no two ways about it. I took her call 'cause I needed the money. That case was dirtier than a first grader's back backpack and twice as heavy. The broad that hired me told me a couple a thugs stole some paper, and I ain't talking about the kind with dollar signs. Some handouts on "Why does salt taste so darn good?" 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. Two teachers: Tammy Lefcourt and Devra Lehman, Asaf, the owner of the local toy store, and the damsel in distress herself, Rebecca Perlin. Each one had his own peculiar attraction to a specific white powder. Tammy and her baking powder; Devra, corn starch; Asaf, sugar; and Rebecca, 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 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.

Wednesday, March 17, 2010

Biology: The Genetics of Blood Types

This week we continued learning about genetics. Once again we carried out a simulation. However, there were a couple key differences from last week:

  • Last week "parents" produced 1 child with a lot of different traits, and this week "parents" produced MANY kids, focusing only on a single trait.
  • Last week the kids looked at made up traits, such as star- vs blast-shaped eyes, while this week they looked at a true example: ABO blood types.
  • Because we had such a large sample size of offspring, we were able to compare the distribution of the different genotypes and phenotypes to what we would predict based on chance alone.

Thursday, March 11, 2010

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.

Physics: Science of swings

This week the kids set out to understand what a swing is by building them out of K'nex and Legos. Once we had a few models to compare, we were able to consider what sorts of changes we could make to the design to affect the swing's period, the time it takes to swing back and forth. The kids came up with a few different variables: the mass of the swing, the length of the swing, and the height or angle at which you start the swing. Next week, we plan to test these variables in the field, on actual swings. Weather-permitting, we'll visit a playground and see which of these variables affects a swing's period the most.

Biology: Chip off the old block

This week the kids carried out a simulation in which they flipped coins to see which genes they would pass on to their offspring, the offspring being different kinds of smiley faces. In this simulation, each parent was heterozygous for the 12 traits carried by smiley faces. Despite the fact the parents all shared the same genotype, the offspring displayed a wide range of variation. We discussed the importance of chance and how the number of potential combinations grows as the number of traits or more accurately, chromosomes increase.

Thursday, March 4, 2010

General Science: Which chip is the greasiest?

Purim is over, and like many of you my house is filled to capacity with chips, candy, chocolate, and other junk. As I sorted through all the snacks I couldn't help but wonder...which potato chip is the greasiest and more importantly, how can I be sure?

Today the kids helped me with these questions 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 performed a more quantitative test where they crushed 3 grams of each chip on a piece of graph paper and then compared the different oil stains. Some kids decided to weigh the paper before and after smashing the chips, some compared how translucent the paper became, and others did their best to count the squares.

Then we tested our TESTS. We read the nutritional information on the wrappers and reviewed our data to see which test was actually the best. Surprisingly the touch test was the most accurate. The kids concluded that the oil stain test could have been improved by controlling how people crush the chips and for how long.

FYI Osem Chipsy Chips contains more fat than Herr's Ketchup Chips or Pringles (sour cream and onion).

Tuesday, March 2, 2010

Physics: Build a motor

As you may remember, a while back the kids magnetized an iron nail by wrapping it in many loops of wire and attaching the ends of the wire to a battery. This week the kids expanded on this principle to build a motor. Once again they made a coil of wire and inserted it into a circuit by resting it on 2 metal struts attached to a battery. Then they placed a small round magnet on top of the battery. The electro- magnet (the loops of wire connected to the battery) and the regular magnet exerted magnetic pulls and pushes on each other so that the coil rocked back and forth.

To make it spin, we had to get creative...the kids put white out on the tops of the wire where the coil made contact with the metal struts. Doing this broke the circuit half the time. What did this do? When the circuit was closed, the coil became magnetic, which gave it an initial push away from the other magnet. As the coil made half a turn, the circuit turned off, and the momentum kept it spinning, bringing the coil full circle.

In a perfect world, the coil would continue spinning until the battery ran out, but alas, we don't live in a perfect world. Besides gravity and electromagnetic forces, the kids had to contend with the most challenging force of all....FRICTION. The need to reduce friction explains why this activity took an hour, and not 5 minutes, and why by the time they got home, the motor may have stopped working.