Tuesday, November 26, 2013

Chanukah science...spinning tops

What do bicycles, frisbees, yo-yos, hula hoops, dreidels, and even the earth have in common? They all spin, and so long as they spin the better they are at resisting what gravity is trying so hard to get them to do, which is tumble and fall.

This week we talked about how dreidels work and then we observed the optical illusions produced by spinning tops with different colorful patterns. We finished up by making our own tops using old CDs.

Chanukah science...Which oil is the most miraculous?

In anticipation of Chanukah we investigated different oils and candles to see which one burns most efficiently.* We tested each oil or candle by measuring the mass before and after letting the wick burn for 3 minutes  We concluded that the one that lost the LEAST weight was the most efficient fuel source, and also the most miraculous.

*inspired by Amitai Levy and Roey Roth's 2008 science fair project

Chanukah science...Candles, air, and a bowl of water

This week the kids explored the effects of using a graduated cylinder to cover a lit candle standing in a bowl filled with water. What happens and why...these were the questions we set out to discover. Some of the results were easy to spot. Others required repeating the experiment multiple times.

Tuesday, November 19, 2013

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!


This week the kids were challenged to reverse engineer a catapult. Presented with some old broken catapults, the kids had to figure out how they were made. Then, using slightly different materials, they modified and improved this initial design to produce catapults of their own. These catapults are examples of a 3rd class lever .


The daffodils we planted in the yard are just starting to emerge from the ground. We can see a few tiny shoots. On the other hand, the bulbs growing inside show visible changes day-to-day. That's why we decided every kid should have a bulb of his own to plant and observe at home. Weekly observations just aren't enough! The kids made special diaries, "daffodiaries," to keep track of how their bulbs develop.

You can plant a daffodil outside in the soil, but we decided to "force" our bulbs to grow indoors without soil, so that we could better observe the changes.  The downside of doing it this way is that the daffodils will take in fewer nutrients for NEXT year's growth. With the exception of water and sun, everything the flower needs is already packed inside the bulb.

With that in mind, here's what we're going to do when we get home:
  1. Find a small glass bowl. 
  2. Fill it with some rocks, marbles, legos, etc. 
  3. Place the bulb on the rocks/marbles/etc. pointy side up.
  4. Pour just enough water into the bowl, so that ONLY the base of the bulb is under water.
  5. Leave the bowl in a sunny spot, and wait and see.
Within a day or two we hope to see roots, and not long after, a shoot coming out of the top. We just need to make sure that the roots have water, and that the plant gets enough sun.

Monday, November 11, 2013

Make like a tree and LEAVE

Continuing our unit in plants, we started to discuss leaves and their role in producing food for the plant. We took a walk outside and collected leaves, and then we classified each one according to its
  • general anatomy: simple or compound
  • margin: simple, serrated, or lobed
Next week we'll finish graphing our results to see which leaf types are the most common.

It's only been a week!

Not much going on with the bulbs we planted outside, at least not much that we can see, but WOW...the bulbs growing inside are unstoppable. After a day or two, we could already see the roots coming down from the basal plate, and after 3 or 4 days, a tiny shoot started to emerge from the top of each bulb.

How many 3rd graders does it take to change a bulb?

This week we started our unit on plants with a discussion of bulbs, that is a type of plant that uses an underground storage system for everything it needs to grow. After comparing and contrasting different kinds of bulbs including onions, garlic, and daffodils, we dissected a daffodil bulb, noting the scales, providing food for the young plant to eat as it grows; the basal plate, where roots develop; and most amazingly, the miniature leaves, stems, and flower parts.

Finally we planted daffodil bulbs both in the soil and in a glass bowl, which will remain indoors.We're looking forward to tracking their progress

Separating Inks

This week we separated yet another mixture - in this case, the ink you find in a typical water-based marker. To do this we used a technique called chromatography. Using the marker we wanted to investigate, we drew a line on a piece of filter paper. Then we dipped one end into a bowl of water. As the water traveled up the paper, it dissolved some of the dyes in the ink. Because each dye has different properties, they travel through the paper differently, and as a result separate into bands of different colors.

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!


This week we started talking about simple machines. The first machine we looked at was the lever. After discussing the 3 classes of levers and examples of each, we experimented with a class 1 lever, the seesaw. Each lab group was given a pair of unequal weights. The goal was to figure out how to place them on the seesaw, so that they would be perfectly balanced. In each case we recorded the distance from the fulcrum. After trying out several different pairs, we reviewed our data and looked for patterns.

Let's see how much YOU know about levers...If you place a 500 g weight 10 cm from the fulcrum, where do you need to place a 100 g weight so that it will balance the heavier weight?

Catch me, I'm falling!

Why do some objects fall faster than others?

We reenacted Galileo's experiments in Pisa to test whether an object's weight influences its speed. After a quick trip up the Leaning Tower of Raanana (aka my stairs) like Galileo, we concluded that weight DOESN'T matter, and that how fast an objects falls is the result of an object's air resistance, i.e. the friction between the object and the air as it moves.

From there we naturally moved on to the subject of parachutes, objects specifically designed to maximize air resistance to keep jumpers from hitting the ground too fast. We dropped balls of modeling clay with and without home-made parachutes and compared flight times and the effects of hitting the ground on our jumpers.

See this TED ED talk for a great way to think about gravity

As an extra bonus this week, we also caught the solar eclipse. Thanks to my husband, Danny for the heads up about the eclipse and for showing us how to safely project the image of the sun on to a white board using binoculars. Of course, you should NEVER look through a telescope or binoculars to point them at the sun. Doing so can result in partial or total blindness.

Melting Away

This week we investigated what happens to the temperature of ice as it melts. We measured the temperature every minutes for 10 minutes, while checking to see if the water was solid, liquid, or gas.

Initially the temperature was a FREEZING -10° C. Not surprisingly the temperature started to rise, but then something funny happened.  As the temperature approached 0° C, it stopped changing. Yet, the ice was still melting. Clearly heat from the surroundings was being absorbed by the ice, but to look at the temperature, you'd never know it. Then, as soon as all the ice was melted into water, the temperature started to climb once again. 

From this experiment we learned two things: 
1) The freezing point of water is 0° C
2) At this temperature, the energy flowing from the environment into the ice is being used to change the water from a solid to a liquid, resulting in a constant temperature until all the water is in the liquid state.  

We see the same thing happen as substances move between liquid and gas states.

Friday, November 8, 2013

Slip sliding away

The kids took what they had learned previously about friction to the field. We spent the first half of the lesson planning out a controlled experiment to compare the "slidability" of different materials. Then we walked to Park Mapu, where the kids worked in groups measuring the time it takes to go down the slide on a range of materials including: a towel, a piece of card board, and a fleece blanket.

Popcorn Science

This week we did a little popcorn science, the questions being: what happens to the mass and volume of popcorn after you pop it and why does heating kernels make them pop? 

We measured the mass and volume of a sample of kernels and then threw in some oil (30 ml / 23 g to be exact). We put all the popcorn into a pot with said oil, turned on the stove, waited, and then POP! We took out the popcorn, weighed it, measured the volume, and here's what the kids concluded: The kids predicted the volume would increase and so it did...practically by a factor of 10. The mass, on the other hand decreased a tiny bit. 

As for why the heat makes it pop...turns out there's a tiny bit of water inside each kernel, which when heated expands and exerts enough pressure to burst the kernel open. As each kernel "explodes", its volume increases while at the same time allowing a small amount of water to escape, accounting for the slight decrease in mass.

Measuring the Volume of Stuff That's Shaped Kinda Weird

We learned a new use for graduated cylinders. Turns out they're not just good for measuring the volume of liquids, but used cleverly can help us measure the volume of objects that are shaped kinda weird. When it comes to simple shapes, like a block, you can use a ruler to measure the different dimensions, but with something like a screw or a paper clip, how do you figure out EXACTLY how much space it takes up? Here's a clue: What happens to the water level when you get into the bath and why?