Re: Stop using calorie?

[herbgottlieb@juno.com]

 EDT LUDWIK KOWALSKI  writes:


> On 21 Sep 1997 Herb Gottlieb wrote:
>
> How do you explain Joule's  paddle wheel experiment WITH calorimetry?"
I have >been explaining that  the work done (by the falling weights
attached to the paddle wheel)  resulted in an increased temperature of
the water of known mass in 
> the tank. This explanation does not require any calorimetry.
>
> Without being too philosophical (about explanations) let me pretend of 
> being your unusual student. "Staying in school yesterday I was 
> repeating the demo and noticed that the change of temperature is smaller
when 
> more water is added to the cylinder. Why is it so?"
Again, it is much simpler to answer such a question without referring to
calorimeters, calorimetry, or caloric.   

By doing the paddle wheel experiment, it was established that 4186 joules
of mechanical  energy (newtons times meters) is required to change the
temperature of one kilogram of water one degree celsius.  Using more
water with the same amount of input energy could not possibly result in
the same increase of temperature.

Ludwik...  I still do not understand how reference to calorimetry would
simplify your  response to this unusual student. However, I do believe
that there is justification in teaching calorimetry  as an outmoded
concept that has historical significance and has helped science progress.


Herb Gottlieb from New York City
(Where we still teach calorimetry because teen agers are very weight
conscious here)