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!

Seesaws

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.

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?