heat

The Leidenfrost Effect – revisited

Time to get back into the blogging game.

I made this video some time  back about an interesting phenomenon called The Leidenfrost Effect:

then came across the following from

thanks to 

Now that was cool

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Firewalking; a wonderful introduction to heat

I introduce Heat Capacity by asking the following question: How come, when you get up in the middle of the night to take a pee, and walk across both tile and carpet, the tile seems much colder than the carpet even though in reality both are at the same temperature (room temperature)?
It introduces the concept of thermal conductivity, and also acts as a reminder to why we need objective measurements in science.

This video on firewalking would make a wonderful follow-up activity, and might just make some a little wary of  ‘life-coaches’.

Thermal conductivity and Low heat capacity; Firewalking explained in terms of taking a cake out of an oven.

Would work at both Junior or Senior cycle.

So how could you design an experiment to ascertain who is right?

And then while we’re here at all, let’s look at an intertaining presentation by Michael Shermer on debunking pseudoscience.

From http://www.ted.com; part one of two. The second half is also well worth seeing.

Horrible Experiments

There are four mandatory experiments to do with Heat on the leaving cert syllabus.
And we always do them.
And, apart from the first, they can all give horrible (and I mean horrible) answers.

I warn the troops in advance and suggest that a percentage of under 30% would be acceptable. It’s not unusual for a student to get a percentage error greater than 100%.
But they generally don’t calculate this untill they are writing up the experiment at home.
They don’t ask about it in class because they probably think that they would just be highlighting their own incompetence, and I don’t mention it because I also am a little embarassed by their results, knowing that they were only following my instructions.

Am I the only teacher who is this inept?
Do many others check?
What do I know? As I keep saying, in this business once we close that classroom door we become kings of our own classroom, and it wouldn’t be unusual for a teacher to go from their own secondary school as a student, up until the day they retire, having only ever seen one other person (their old science teacher) teach any given topic.
This can’t be right.
Can it?