Message-Id: <334DBEB2.3671@postoffice.pacbell.net>
Date: Thu, 10 Apr 1997 21:31:46 -0700
From: Guido van Rijn <vanrijn@pacbell.net>
To: pinhole@exploratorium.edu
Subject: Re: Calory counter
Pinhole Listserv wrote:
>
> Don't miss the simple calorimeter in the Exploratorium Quarterly Food issue.
>
> Burn a peanut under a test tube containing a measured 10 mL of water.
> measure the amount of water left after the burning ends.
> Use the temperature increase from room temp to 100C and the amount of water
> boiled away (2 mL) to calculate the energy delivered by the burning peanut
> to the water.
>
> Paul Doherty
Seems like an awful lot of heat loss. Try taking a tin can with both
sides opened - to be used as a combustion chamber. Wrap a paper cup in
some tin foil so that it sits inside the opened tin can. Fill with 50
ml (grams) of water. Make sure there are openings at the bottom of the
tin can and at the top so that you have some air flow. I use corks
wrapped in aluminum foil with a pin sticking out the top to hold a
peanut, cashew, popcorn, etc.
1. Measure the mass of the "peanut" on the pin prior to burning.
2. Measure the mass of the "peanut" after burning. The difference
represents the amount of "peanut" actually burned (i.e delta m).
3. Obtain the change in temperature of the water (delta T).
4. Multiply this change in temperature by the specific heat of water
(sp. Ht. = 1) and again by the number of grams of water (50g). This
should equal the total number of calories released by the burning
"peanut".
4. Divide by the number of grams of "peanut" that was actually burned
and you get calories per gram of "peanut". don't forget that food
calories are actually Kilocalories - so - divide by 1000 to get
kilocalories per gram.
This pretty much describes my annual piromania lab that I do with my
Physical science students.
By the way. Isn't there a way for us to actually send files back and
forth. Could we not exchange actual lab experiments that we use in
classes by sending them along as attachments? Just a thought.
Guido van Rijn
Burlingame HS