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!

Milk Mixer

What happens when you add a few drops of food coloring to water? What about milk? What happens when you put some soap on the end of a toothpick and gently touch the surface of the milk containing the drops of food coloring? Let's just say, it gets pretty psychedelic.

It's the chemical reaction between the fat in the milk and the soap that causes everything to swirl around, so we decided to compare the effects of using heavy cream, 3%, and 1% milk.

As if we didn't already have our hands full tie-dying milk, we took some non-soapy cream, shook it up inside a glass jar, and made some creamy delicious butter.

Our conclusion: Milk fats are yummy and fun!

Water, water, everywhere!

When it comes to space exploration, nothing makes the news quite like the possibility of finding extra-terrestrial water. Just over a month ago,  a research team from Japan used the Subaru Telescope to observe the water-rich atmosphere of Gliese 1214 b, a planet 40 light years from Earth.

Why are we always searching for water in space? What does discovering water have to do with the possibility of discovering extra-terrestrial life? 

To begin answering these questions, we explored some of water's interesting properties through the following investigations:

Water's molecular structure: We made models of water molecules, noting how oxygen and the 2 hydrogens share electrons.

Water sticks to other water molecules and other stuff too: We observed the U-shaped water line in a graduated cylinder and the dome shaped water line, as you fill a cup just beyond the brim.

Water is strangely denser than its solid form, ice. 

Water's a great solvent: We saw how water dissolves marker ink and carries along its components through filter paper.

Finally we discussed why these properties are so important for life as we know it.

Etrog vs. Lemon

With the holidays just wrapping up, studying etrogs from a biological perspective seemed like a great way to kick off Science Explores aka Life Science. The etrog, more commonly known as the citron, belongs to the citrus family of flowering plants. Etrog trivia: The "pittom" is which part of the flower?1

Then we asked the question: Is an etrog simply an over-priced, funny-shaped lemon, or is there more going on?2 We made some external observations, noting their shape, color, volume, mass, and density. Then we opened them up and looked inside. Turns out, there are some interesting differences in the relative proportions of peel, fruit, and juice volume. We measured each fruit's pH, and then celebrated a job well-done to the tune of a tall glass of lemonade. Due to the lack of juice, the etrogade wasn't as successful.

More ETROG TRIVIA...
"Flavedo" and "albedo" are
a. the yellow and white parts of the rind
b. trapeze artists, as in "The Amazing Flavedo and Albedo"
c. great scrabble words, well "flavedo" anyway
(3)

Answers
1. The stigma, the part that receives pollen grains
2. There's more going on 
3. a.

Ice cream in a bag!

This week we did a pretty COOL trick....we made ice cream, without a freezer, without an ice cream machine. How did we do it and what does it have to do with science?

First we demonstrated that ice covered in salt will melt faster than ice alone, and most surprisingly that the liquid salt water is actually COLDER than the frozen ice. We then discussed how phase change, or matter moving back and forth between solid, liquid, and gas states, involves a transfer of energy or heat. In other words, when there is a phase change, heat is absorbed in one direction and released in the other. These ideas and observations formed the basis of our ice cream experiment.

The kids poured the ice cream ingredients (milk, vanilla, and sugar) into a small plastic bag. Then they placed this bag into a larger bag filled with a lot of ice and a lot of salt. The whole business was then wrapped in a towel and then shaken until the milk mixture solidified. The rock salt caused the ice to melt quickly and reach a sub-zero temperature, so that the resulting freezing salt water could quickly absorb heat from the milk mixture, giving you yummy, delicious ice cream or at the very least, a super-cool milk shake.



Here's the procedure in case anyone wants to try it at home.

1. Pour ¼ cup of milk into a sandwich-size zip lock bag.
2. Add 1 teaspoon of sugar and a couple drops of vanilla extract.
3. Close the bag carefully, while getting rid of the extra air.
4. Mush the bag around to mix the contents.
5. Place this bag in another sandwich zip lock bag, remove the extra air, and seal.
6. Fill a 1-gallon zip lock bag with ice and a half a cup of rock salt.
7. Place the double bagged milk mixture inside the larger bag, squeeze out the extra air, and seal.
8. Wrap each bag in a towel and mix, shake, and churn until the inner bag's contents freeze.

Tips:

* Make sure all bags are closed, especially before you start shaking up the bag of ice and salt.
* Double-bagging the milk mixture is important, to help reduce the odds of salt penetrating the bag and getting into the ice cream (yuck!).
* Err on the side of too much ice and too much salt.
* Try to keep the milk mixture bag in the middle of the ice, and especially in the middle of the melted salt water.
* See what happens if you add different flavors like chocolate syrup or lemon juice.

Chemistry in a bag

The kids started off with calcium chloride, sodium bicarbonate (see if your kids remember this compound's common name...it's baking soda), water, and phenol red, an indicator for acids. They put all of these materials in a plastic bag, the catch being that the liquids (water and phenol red) were first poured into plastic cups, which themselves were carefully placed in the bag. Why all the extra steps? This allowed us to measure the whole business BEFORE the chemical reactions began. After tying off the bag, the kids allowed the powders and liquids to mix, and that's when things got exciting! The kids observed many changes including: bubbles, the bag inflating, the red liquid turning yellow, and the contents both heating up and cooling down. The kids then measured the weight of the bag with its contents, and they were pretty surprised to find very little if any change. That's conservation of mass for ya! Step 2 of this experiment was breaking down the reaction into parts to see what happens when you combine different pairs of ingredients.



Chugim will run as usual next week for all groups, INCLUDING Tuesday's sessions, which will meet at their usual times.

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!

Quiz: Etrog vs Lemon