Wednesday, December 31, 2008

General Science: Elements we know and love

This week we in introduced the Periodic Table of Elements. At first the kids were a bit overwhelmed by all the scary looking numbers and letters, but on closer inspection, they realized that there were a lot of elements they know quite well. After talking a bit about different elements the kids carried out an experiment in which they explored the properties of sulfur and iron using a magnifying glass, a microscope, and a magnet. They combined them, and then assessed 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 decide!

Chemistry trivia: What are the chemical symbols for sulfur and iron? Ask your kids and let them show off their Latin!

Wednesday, December 24, 2008

General Science: Plant cell and animal cells...up close and personal

Last week we continued our investigations with microscopes. Having already gotten some experience with the ins and outs of using a microscope, we focused on different kinds of cells. The kids got a chance to compare plant and animal cells by extracting human cheek cells (sounds much more painful than it actually is) and onion cells (a little smelly, but otherwise no tears). We talked about how animal cells are more "blob-like," and plant cells have a rigid exterior, which makes them look like boxes or bricks.

Physics: Build a motor

This week the kids built motors. First they made a coil of wire which rested on 2 metal struts attached to a battery. When connected to the battery, the coil became an electromagnet. Then they placed a small round magnet near the battery that was connected to the electromagnet. The 2 magnets: the regular one and the electromagnet 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. When the circuit was broken, it was the momentum of the coil itself that carried it through the second half of the spin. 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 another challenging force.... 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. I guess you could say the kids got a lesson in real-world engineering. A bit frustrating, but definitely builds character!

Physics: What color is it really?

We all know what happens when you mix yellow and red paints...what happens when your brain does the mixing?

This week we did 2 mini-experiments to investigate how we perceive color. The first one was with spinning color wheels - discs with various color patterns, which when spun reveal different colors. The second involved examining magazine pictures under the microscope.

Both experiments demonstrate that what we see is limited by how much information our eyes and brain can take in at once. With the spinning color wheels, when we see 2 colors within a short period of time, our nervous system combines the colors. Pictures in a magazine, like the paintings of Seurat (did I mention we got all cultural and talked a bit about pointillism?), are actually made up of patterns of tiny dots. When the dots are small and placed closely together, your brain can't process them separately and instead combines them to produce the experience of various colors. What is especially cool about the magazine pictures is that no matter what color you "see," the image itself is actually made up of just 3 colors: magenta, cyan, and yellow (aka red, blue, and yellow) plus black. By producing images that include different ratios of the primary colors, you can get just about any color.

Thursday, December 11, 2008

Physics: Making Magnets

Last week the kids discovered that iron-containing metals can themselves becomes magnets if they are rubbed by a magnet. We used this observation to build compasses in 3 easy steps:
  • Rub a light-weight iron needle with a magnet 50 or so times.
  • Stick it through a thin piece of Styrofoam.
  • Set the whole business afloat in a bowl of water and observe how, try as you might, you cannot prevent the needle from pointing along a north-south axis.
Afterward, the kids built electromagnets. It turns out in an electric circuit, the movement of electrons creates a magnetic field. Because it is quite weak, you might not notice it. One way to increase it's strength is by building a circuit with MANY loops of wire, with each loop reinforcing the strength of the magnetic field. In our case, the kids wrapped wire around an iron nail. The kids explored the effects of changing the number of loops on the strength of the electromagnet.

Wednesday, December 3, 2008

Physics: Magnetic Muscle

This week the kids did several mini-experiments on magnetism.
  • They tested various materials around the house to see if they were magnetic.
  • They compared different magnets to see which one was the strongest.
  • They explored the effects of rubbing a magnet on an iron nail...apparently being magnetic is contagious!
  • They observed how magnets influence the pointer on a compass.
  • They mapped out magnetic fields by observing the behavior of iron filings in a plastic container placed next to a magnet.
Next week the kids will use what they have learned to build a compass.

General Science: It's a gas and "Ooblek"

For our experiment this week, we did an oldie but a goodie...what happens when you combine baking soda and vinegar?
Perhaps because of some past experience building volcanoes, 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?!) But more than that, they observed that the mixture of baking soda and vinegar interacts with a lit candle differently than would vinegar or baking soda alone. Passing a lit candle over baking soda had no effect on the flame. Same deal for the vinegar alone, 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. Those are your bubbles, and they have the property of putting out a fire. That's why they put it an actual fire extinguishers. Cool, huh!?

Afterward the kids mixed cornstarch and water to create a really neato substance. What's so cool about "oobleck?" Well, it behaves like a liquid until you apply pressure to it. Then it behaves like a solid. Check out this video to see what I mean.