Tuesday, January 24, 2012

Biology: Homeostasis...the final verdict

We spent this past lesson analyzing our data using Excel. Each kid entered and analyzed one of the 5 sets of data we collected. Then we discussed our results. Most of our results fit in with what we know about how the body maintains homeostasis. Following exercise our heart rate and breathing rates increased in order to bring in more oxygen and sugar, and at the same time rid our cells of accumulating waste products.

Our data on body temperature were somewhat contradictory. While on average body temperature decreased, subjects sweated more and their skin color reddened over time, both of which are ways our body regulates increasing body temperature. We all agreed that measuring body temperature is difficult and subject to a lot of error. But there's hope...

Following our analysis we read an article about the CorTemp temperature pill that can record body temperature and heart rate data continuously and wirelessly transmit this data to an external device for graphing and archiving. The pill has seen many applications in the real world for athletics, for the military, for monitoring of animal vitals, and my personal favorite...for helping food companies test exactly how much heat a hot dog can tolerate before it becomes overdone.

Physics: Good Vibrations

This week we started a new topic: SOUND. We talked about what a sound is and experimented with sounds produced by different materials. The kids made oboe-like straws, plucked rubber bands of different widths and lengths across shoe boxes, bounced wooden sticks off the side of tables, and struck water-filled glass jars, noting in each case how different changes affected the pitch. Finally, the kids used their observations to created their own instruments, and then we had a concert!

Physics: Pulleys

Our goal this week was to raise a 300 g weight a distance of 30 cm. To do this we used a new kind of simple machine, the pulley. We built 3 different kinds, and in each one analyzed the user's experience.
All pulleys PULL, but up or down? How much string do you need to use? and most importantly...Does it feel any easier than just lifting the weight on your own?

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!?

Thursday, January 19, 2012

Biology: Homeostasis, new and improved

After 2 weeks of brainstorming, trying out mini-experiments, and working out the logistical details of how to simultaneously measure a whole bunch of different things within a short period of time, we finally carried out our new and improved homeostasis experiment. Each kid ran for 6 minutes, while the rest of the crew made observations of body temperature, skin color, perspiration level, heart rate, and breathing rate. We'll analyze our results next week.

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.

Thursday, January 12, 2012

Biology: Homeostasis

This week the kids completed their experiment on the effects of different physical activities on body temperature. The results were quite surprising. After performing activities, subjects' body temperature stayed the same or went down. Afterward we discussed sources of error and decided that there were some design issues we wanted to change. Most importantly the kids wondered whether carrying out an activity for one minute would be enough time to produce a measurable change. The kids spent the rest of the class planning out a more extended experiment in which subjects will perform 10 minutes of physical activity and the kids will observe a number of physiological changes in addition to body temperature, such as heart rate, skin color, and amount of sweating. Next week they will carry out this experiment.

Friday, January 6, 2012

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!

Wednesday, January 4, 2012

Biology: Feeling hot hot hot!

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 on body temperature. Next week they will analyze their data and present their findings.

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!