Cells, up close and personal

This week we continued our investigations with microscopes. Having already gotten some experience last week with the ins and outs of using one, we focused on 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 how plant cells have a rigid exterior, which makes them look like boxes or bricks. 

Afterward the kids looked at other specimens under the microscope including: a mosquito (the wings are really interesting up close), a spider (much hairier than you'd think) , a louse (even scarier magnified 100X), a blade of grass, and various leaves.

Whisper words of wisdom, letter "e"

This week we learned how to use a compound microscope. First we reviewed the parts of a microscope and what they do. Then the kids learned how to prepare a wet mount (a slide with a specimen + a drop of water and a cover-slip) The first specimen the kids examined was a lower case "e." When it comes to the letter "e," there's more than meets the eye. It doesn't just get bigger...

After we got the hang of things, we looked at some serious specimens. If you think spiders are scary, try looking at one magnified 400 times!

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!

Biology: Measuring tiny things

This week we learned a technique for measuring the length of tiny things. The kids measured a louse (for the uninitiated that's singular for lice), onion cells, and a human hair. This activity gave new meaning to the question: Do you have thick hair or thin hair?

So what unit do you use when you're measuring something so small? Meters, centimeters, millimeters? At this scale we're talkin' microns, 1000 of which make a millimeter. Using a ruler, the kids measured the field of view. Then they converted this number to microns. After examining a specimen, they estimated how many times it would fit within the field of view, did some simple math, and came up with a measurement that was within 2.5% of the accepted value. Not bad for a day's work!

Physics: What color is it really?

This week we did 3 mini-experiments to investigate how we perceive color. The first was with spinning color wheels. The kids compared the patterns of the discs when still to the patterns they saw when the discs were spun. The second mini-experiment involved looking at magazine pictures under the microscope and comparing the images seen with the naked eye to the colors seen at greater magnification. The third was simply giving each kid some red, blue, and yellow paint and letting them go wild...well on paper anyway.

When we physically combine red, blue, and yellow paints in different proportions we can create an enormous range of colors. Similarly the human brain will combine colors that your eyes see when those 2 colors are seen in rapid succession, as in the case of the spinning color wheels or when they are placed very close together, as revealed by a microscopic examination of pictures from a magazine. What is especially cool about the magazine pictures is that no matter what color you "see," when examined under the microscope you realize that the image is made up of just 3 colors: magenta, cyan, and yellow (aka red, blue, and yellow). By producing images that include different ratios of the primary colors, you can get just about any color.

Biology: Water...more than meets the eye

This week the kids 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!