Friday, February 17, 2012

General Science: Which chip is the greasiest?

This week in science we asked the following questions: which brand of potato chip is the greasiest and more importantly, how can I be sure?

We went about answering them 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 were challenged to come up with a more quantitative test, one based on measurement. Some kids crushed equal amounts of each chip on a piece of graph paper and then compared the sizes of the different oil stains. Others compared the weight of the chips before and after crushing; the assumption being, the greasier the chip, the more oil lost in the act of being crushed on a piece of paper. Another test consisted of soaking different chips in water, removing them, and then comparing the amount of oil observed sitting on top of the water.

Wednesday, February 15, 2012

Physics: Batteries

This week we introduced a new topic: electricity. We started off by examining some batteries, taking note of things like voltage and the fact that every battery has a positive and a negative terminal. After a brief discussion about what batteries are and how they work, the kids made batteries out of grapefruit and strips of copper and zinc. Using a voltmeter we confirmed that our batteries worked. A single grapefruit has a voltage of around 1 v, which compared to your 1.5 v AAs is no small potatoes (FYI potatoes make great batteries too)! We attached wires to the battery, hooked up an LED, and NOTHING. Apparently 1 v is not enough voltage to power an LED. But, when life gives you lemons,make lemonade, or in my case, when life gives you a grapefruit tree, make several grapefruit batteries in series and voilà! Let there be light!

Monday, February 13, 2012

Biology: What are bones made of?

Over the last 2 weeks we have been investigating bones. We tested the effects of heat and acidic solutions on chicken bones. After placing bones in the oven, the kids observed that they became more brittle. On the other hand, bones soaking in vinegar lose their rigidity and become flexible. What do these two experiments demonstrate about the main components of bone? Bone is made up of collagen, a protein that gives bones flexibility, and calcium phosphate, a mineral that gives bone its strength. Heat destroys the protein, and vinegar dissolves the calcium phosphate through an acid-base reaction.

After these experiments, we reviewed the bones in the human skeleton and then did some comparative anatomy as we tried to identify various animal bones.

Physics: Sound waves

This week we continued exploring sound. We used slinkies to model how sound waves work and then spent some time experimenting in this really cool online sound lab.

General Science: Solutions

This week we learned about solutions, that is liquid mixtures. In particular we wanted to know whether water temperature affects how well something dissolves. First the kids compared the time it takes to dissolve a couple drops of food coloring in different water temperatures. Then they tried to see how much sugar they could stir into solution, once again comparing different water temperatures. They concluded that hot water is much more effective at dissolving solutes (that's fancy-talk for stuff).

We also noted that the final volume of the sugar solution was surprisingly LESS than the sum of the initial water volume plus the sugar. Part of what happens when you dissolve something is that it breaks up into tinier pieces and more spaces open up within the molecules themselves.

General Science: White powders

This week we continued our exploration of physical and chemical properties by investigating 4 different white powders: sugar, salt, corn starch, and baking soda. The physical properties we investigated included: how each one looks under the microscope and how each one feels. As for chemical properties, we combined the powders with vinegar and iodine and recorded the results. Finally we looked at whether any of the powders conduct electricity when dissolved in water.

The kids now have a comprehensive data sheet on these substances and their physical and chemical properties. If by chance, they should come into contact with some unknown white powder, making an identification should be a piece of cake!

One never knows when these skills and/or data might come in handy...

Thursday, February 2, 2012

Physics: E.T. phone home

While we're on the topic of sound I thought it would be a great time to learn how to make cup-phones. Problem is I had never really done it before. I knew we'd need cups and string, but what kind of cups? Thick string or thing string? Does the material matter? Tough questions, but lucky for me, like Thomas Edison, I've got a stable of engineers in my very own Menlo Park. Given a range of cups and strings to choose from, the kids tested out different models. By the end of the hour I expected a full report on how to make the best cup phone and time-permitting, the pros and cons of various cell-phone plans.

Biology: Acids and Bases

This week we started a new topic:  acids and bases.  First we used litmus paper and pH paper to classify different household liquids.  Then we boiled up some purple cabbage. Cabbage broth has the interesting property of indicating for acids and bases.

The kids added cabbage juice to the different liquids and observed the results. They recorded the color changes and using the pH values, ordered the cups according to where they fall on the scale. 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.


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.