Chemistry That Matters

 Our second class finished our study of Matter - next week we will move on to Forces.

We started out with inertia.  Each child had a mason jar with a playing card set over the mouth of the jar, and a quarter sitting on top of the card.  If you flick the card with your finger, the card shoots out and the quarter (because of it's inertia) stays in place until gravity causes it to drop into the jar.

I was a bit concerned that the 5 year olds in the class wouldn't have the dexterity to flick the card, but they were great!  I think it helped to use the slippery playing cards rather than the index cards the book called for on this one.

Next we looked at changes in matter: physical changes, phase changes, and chemical changes.

 Starting with the physical, I held up a 4x6 index card and asked the kids if I could stretch the card all the way around me.  I pulled and tugged at the card, but they didn't think I could do it.

I proposed that I cut the card to make it longer.  Well that was a hilarious suggestion!  Everyone knows cutting things makes them shorter!

Except this zig zag cut stretched the card out to about 4 1/2 feet! (Yes, it did fit around me.)

Moving on to phase changes, I handed each kid an ice cube and let them put it in their mouth.  Of course the ice turned to water. I then passed around a mirror and had them all breathe on it so that they could see the water vapor.

Presto!  All three common forms of matter...in their mouths... at the same time!

I skipped demonstrating a chemical change (although we talked about it) in favor of the kids suggestion that we microwave the ice cubes and watch what happened. Better to nurture the spirit of inquiry than get through my lesson plan!

We talked about atoms, particularly the fact that the nucleus was positive and the outer shells are negative.  We demonstrated by letting the kids rub balloons on their heads and then using the charged balloon to make confetti (thoughtfully supplied by my 3 hole punch) "dance."

 I mentioned that atoms are always in motion and that this energy we perceive as heat.  I filled one jar with chilled water, one with room temperature, and one with hot water.  Then I dropped some liquid watercolor into each jar.  The watercolor dropped to the bottom of the cold water, swirled about in the lukewarm, and diffused rapidly in the hot.  I'm always surprised at how fascinated kids are by this.  It's easy and virtually no mess - I should do it more often!

I wanted to look at how atoms and molecules interact, so I filled one jar (far left) with two cups of water. Mason jars are great for this because they have measuring marks on their sides (but use an accurate liquid measure to put the ingredients in!).

For the next jar, I put in one cup of water and one cup of 91% isoproponal (rubbing alcohol).  That's the middle jar, and you can see it doesn't measure up to the whole 2 cups!

In the jar on the right, I put one cup of sugar, and one cup of water then put on a lid and let the kids shake it! In that jar we are "missing" about a 1/2 cup of matter!  The sugar and alcohol molecules slid between the water molecules which takes up less space.

Lastly, we played around with density.  The floating egg is in a salt water solution.  The sinking egg is in plain water with a few drops of milk added to mimic the look of the brine. It was a close enough look that I couldn't tell them apart without the eggs!

I had intended to do a little more density by asking them the "What weighs more, a pound of feathers or a pound of coins?" question, but I forgot it until I reviewed my notes.

The way that I like to explain to little kids about mass and density is this:  have them jump as hard as they can, so they really feel the jolt of their own mass as they land (works best inside on a floor that makes a lot of noise and moves a bit).  Tell them mass is the amount of stuff that they have inside them. Show them that I have more mass, more stuff in me (when I jump, I shake the floor more!).

Then explain that density is how much stuff is packed into a particular space. I like to hand them a golf ball and a ping pong ball.  They're about the same size, but the golf ball has more stuff packed into that space.