Wednesday, August 26, 2009

Week 1 Day 3- Tickets and Exploding buckets and Observation vs. Hypothesis.

Today's Best Practice: "The Ticket out the door". For years I'd collect homework only to find 40% of the class did not turn it in. I'd play the "turn in your homework" chase game. Now their ticket out the door is the assignment handed to me as they walk out the door (I stand in the door). If they do not have it they cannot leave until it is given to me. This can be quite a fight at first. Make sure to make it clear what the "Ticket out" is for the day and it is best if they have to miss the FUN assignment as they finish their work. They will give all sorts of excuses why they cannot stay. Hold firm and tell them ,"then you should have completed it before the end of the period". Now you have to be smart about this. It's easier to do this if Break or Lunch is after class. Missing the bus can really anger parents. If a kid has to catch the bus hold them only a minute or so (to them is seems like an hour). It only takes a few kids to be stunck in class for them to get the idea that it's too much pain and not worth the trouble to miss assignment turn in. Now I am at about 93.4% homework collection.

It is day 3 of the year. I had to learn how you give emergency Glucogon injection for a student with diabedes. Ya, I know...Great! Well the student is a really nice kid so I do not mind. The first day freshness is gone, but all on good behavior. The "honeymoon" is still happening. I've some years that the "honeymoon phase" never ended all year.

The first day or two can have me being a talking head quite a bit. You need to break it up and hopefully give them a thrill in the middle of possible tedium.

EXPLODING CAN!!! I do a demo the first days of school. I fill a gallon paint can with propane (or natural gas, whatever PG&E provides) in the fume hood before class. I have a 3/8 inch hole drilled in the lid and on the lower side. I use duct tape to seal the can.
I tell the kids you can tell when you have a really good seal, it's when you hold it near your ear(I do this) and if you can hear "argh argh argh" its a good seal. 4 kids get it right away, 6 or 7 more in 5 more seconds...then you have to explain you just made a sound like a seal.
I show the can and taped over holes to the students. Then I place the can in safe location away from students and from any doors. I remove the top piece of duct tape and use a lighter to lite the gas. A tiny blue flame occures.

Then I remove the duct tape covering the hole on the side of the can. The flame immediatly grows to a tall 23 cm (10 inch) yellowish flickering flame with tinge of blue at the bottom. Over the next 3 1/2 minutes (time varies with the size of the holes) the flame burns smaller, bluer and steddier until it becomes a tiny half-marble sized blue flame...then...smaller...occasional flicker of orange as a dust mote burns...pea sized flame now...the kids are all wide eyed... and the class is silent...and dark... for I have turned the lights down...
...SCREAMS...SHRILL GIGGLES AND LAUGHTER...the blurbal blurbal blurbal of 30-40 students caught excidedly in mid thrill and all talking at once.


Make sure you know where the lid will go. With a new can, the lid has a tighter seal (never Seal jokes here) and will bounce off the ceiling, often denting the tiles up there. Older cans will only make a calm "PHLEMPH" sound.


Like you need a good excuse to do this demo! But you may have a stingy department head or administrater that says (imagine a real horsey high nasal shrill voice), "What standard does that demo address..hmmf."

Before I do the demo I explain that science is OBSERVING and then HYPOTHESIZING. I review that one is seeing-hearing-feeling and the other is inferring, guessing, drawing on past knowledge. I have them make a simple data table. OBSERVATION and HYPOTHESIS at the top seperated by a vertical line down the notebook page and then as the can burns I promt them to observe and to write down their guesses. We end the demo with discussion of their hypothoses. They end with writing a 1 sentence REFLECTION (what you thought about it and what you learned from it).

SPOILER ALERT: Why the flame does what it does?: Small blue flame to start until you open the side hole, now the gas can easily escape the top as AIR is allowed in. The flame shrinks and changes from yellow(cool) to blue (hot) as less fuel is present but with a better fuel/oxygen ratio. Finally when most gas is gone the flame dips into the can where a perfect ratio of gas/oxygen is present and..kaboom.

Well it's late and I gotta get going.

Love to Teach and Teach with Passion!

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