Sunday, February 20, 2011

General Science and Biology: Butterfly Season

Over the past few weeks the kids have been creating butterflies that are camouflaged in different areas of my house. For each one we recorded the date the butterfly went up on the wall, its birthday and the day it was observed by one of my kids i.e. the day of its death.

Check out some of the most well-adapted ones!

Thursday, February 17, 2011

Physics: What is density anyway?

This week we explored what density is. We started with a comparison of STUFF vs SPACE (i.e. mass vs. volume). Then we measured the mass and volume of 6 different objects. Measuring the mass was pretty straightforward...we used a scale. Measuring volume was a different story. To measure the blocks we used a ruler to measure each dimension and then multiplied them together, and for the irregular-shaped objects, we dropped them in a graduated cylinder filled with water and recorded the subsequent change in volume. Now for the HARD part! To get an idea of just how much STUFF is in a given amount of SPACE, we calculated the density by dividing the mass by the volume. Finally we put each object in water and noted whether it was a sinker or a floater. The coolest part was noticing that the density of all the floaters was less than 1 g/ml and the sinkers were all greater than 1 g/ml, and from this we inferred the density of water - 1 g/ml.
Not an easy lesson, but hopefully it will eventually SINK in!

Wednesday, February 16, 2011

General Science and Biology: Purple cabbage broth...more than just just smelly and blue

This week we boiled up some purple cabbage. Why did we do this? Well, it wasn't simply to overwhelm our senses with its powerful smell and uncanny blue color. Cabbage broth has the interesting property of indicating for acids and bases.
The kids added cabbage juice to 7 different liquids and observed the results. They recorded the color changes and using their data from last week, ordered the cups according the pH values. They observed that cabbage juice indicates strong acids with pinks, weak acids with purples, neutrals with blues, weak bases with greens, and strong bases with yellows. Finally they were given an unknown liquid, and using their cabbage-pH scale they guessed its pH.

In the Biology group we took the analysis one step further. After measuring each liquid's pH with the cabbage juice indicator, we explored what happens to the pH of an acid as we add increasing amounts of a base. The kids started off with vinegar + cabbage juice, giving them a nice bright pink, indicating a pH of around 2. As they added more and more baking soda they were able to observe the vinegar change colors as its pH gradually moved closer to a neutral 7.

Friday, February 11, 2011

Biology and General Science

This week we learned about acids and bases and three 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.

Physics: Depth perception in basketball and football

This week the kids designed and executed an experiment to investigate whether two eyes are better than one when it comes to football or basketball. This lesson was a follow-up to the lesson we carried out two weeks ago, in which we carried out some mini-experiments on depth perception. Reflecting on the difficulties and challenges that came up during these experiments allowed the kids to write a more well-thought-out and developed experimental design for this week's experiment.

All groups found that on average a subject's game was improved with the used of two eyes over one.

Thursday, February 3, 2011

General Science: The Case of the Stolen Handouts

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 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.

Biology: Makes the heart go pitter patter

This week we talked about homeostasis, the idea that our bodies need to keep things inside more or less the same despite an-ever changing outside environment. Our cells need a certain amount of oxygen, water, and energy in order to function. Furthermore, they can only carry out their metabolic processes within a particular range of temperatures. When we are in situations that challenge the status quo the body must do something to compensate.

This week the kids designed and ran experiments to determine the effects of exercise (loosely translated in some groups as consuming hot chocolate and candy) on breathing and heart rate. Next week they will analyze their data and present their findings.

Physics:'s your density

This week we began an investigation of why things float and sink. We looked at a couple different set-ups and made observations. The first thing we looked at were some raisins in a glass of seltzer. What was odd about the raisins was that sometimes they floated and sometimes they sunk. It took a while to figure out what was going on, but then we noticed that the raisins would initially sink, and then after collecting some bubbles from the soda, would take a ride to the top. The second set-up was a simple lava-lamp-like device. Some water, some oil, and then to literally spice things up, we added salt. Globs of oil that had been previously sitting on top of the water were dragged down by the sinking salt. As the salt separated from the oil, these globs would then race back to the top. Finally, the kids filled test tubes with 3 different liquids: water with food coloring, corn syrup, and oil. They observed the layers that formed and then tried adding them to the test tube in a different order to see if that made a difference.

Next week we'll discuss these observations more and try to understand what's going on.