Back to Science Class: Earth Science

I didn't do the science class this week because I was having trouble getting my act together over the weekend. Then again, I hadn't yet posted what I had done last week, so here it is!

I started out talking about the structure of the Earth. I handed out printouts (that show the crust, mantle, core, etc.) and we talked about how the Earth is not a perfect sphere.

To look at why the Earth bulges in the middle, we assembled these nifty contraptions.

You cut out two long thin strips of construction paper and punch holes on both ends.

You thread the holes onto a pencil or pen so that you form a ball with the pen just inserted a little way into the ball (we stapled the part where the strips cross to give some stability).

When you twirl the pen, the ball flattens because there is nothing rigid inside to support the spherical shape.

Since we were already spinning things, I brought out a tray of 18 eggs - half hard boiled and half raw! I asked the kids to figure out which were which... The trick is to spin the egg and stop it briefly. If the egg is hard boiled, it will stay stopped. If it's raw, it will start turning again because the inertial motion of the liquid inside will still be spinning.

Now for the act of faith! Once two Zoomlians agreed that a particular egg was hard boiled, I chopped it in half with one really quick hard blow from a heavy kitchen knife. They were correct! This was one I move I had practiced beforehand. If you do it fast enough, you get a really clean cut and you can use the eggs layers as a model of the Earth with the shell being the crust, the white the mantle and the yolk the core. The core is not to scale (and you don't have an inner core), but the shell is. What I wanted the kids to see was that the crust is a very small, very thin layer of the Earth.

I then crunched up the egg a bit to show how the crust is in pieces (tectonic plates). We then tried to do a continental drift experiment. I was dying for this to work! I had cut up some paper continents and I laid them on diluted corn syrup in a pan on the stove (it was PANgea, get it?). I then heated the pan so that the simmering motion would disperse the continents. Which it didn't.

I had gotten this to work the week before (after a lot of trial and error), but the corn syrup must have formed a matrix with the water after a week in the bottle.

The problem with using water is that the paper absorbs the water and sinks. It's just too fluid. The problem with corn syrup is that it quickly forms a skin that glues the continents together. If you want to try it, add some water just before you use it.

We then demonstrated what happens when plates collide by using newspapers (sliding over and under) and fabric (folded mountains). We talked a bit about the Ring of Fire.

Then it was on to the favorite activity: volcanoes!

I had made play clay with salt, flour, and coffee grounds. To me, the coffee makes it look more like rock. Plus, the grown ups thought it smelled great! The kids were of divided opinion on the smell.

I also had some small plastic soda bottles (maybe a cup volume) and some plastic plates saved from recycling for just such an occasion.

I had a big bag of baking powder and a funnel.

I had a gallon jug of vinegar to which I had added a squirt or two of dish soap and some red paint.

The kids worked in teams to mold the clay around the bottles on the plates. When they were done, they carried them OUTSIDE to the driveway. When I've only had 3 or 4 volcanoes, I've done them in the bathtub, but I ended up with 7, so it needed to be outside!

The kids used the funnel to add baking soda to the bottle. They used between 2 tablespoons and 1/3 cup... Everything works.

I poured in the vinegar! WHOOSH!! Piles of red foam spewing everywhere! Kids shrieking with glee! Grownups taking two steps back! Do it again! Do it again! And we DID.

A perfect class!!