Australia's Science Forum

Hi Everyone,

I have been asked to look for a prac that will test the energy in sugar. I have tried various ways of typing in the question in google and here and have not found what the teacher is looking for.
She suggested that there was a test you could do by boiling up a leaf and breaking down the cellulose but as no one has done that prac since I have been here and I can't seem to find it I am none the wiser.
Please help

I'm not going to be very helpful here except to say that it isn't up to the lab tech to find pracs for the teacher. Having said that what if the students burnt a sweet biscuit like the tiny teddys (little bear biscuits)under a boiling tube of water and see what the temperature of the water gets too. Teddy bears are used in place of peanuts in case students have peanut allergys. Also can someone correct me if I say that the boiling of a leaf (in metho on a hotplate) to break down cellulose is the prerequisite for testing starch in a leaf.
Lyn.

P.S. The peanut/teddy prac uses 10ml of water in the boiling tube. You measure the temperature of the water then light the peanut/teddy and when the peanut/teddy is completely burnt measure the temperature of the water again. "It takes 42J of energy to raise the temperature of 10ml of water by 1 degree centigrade. Multiply the rise in temperature by 42. " This tells you how many joules of energy were transferred from the peanut/teddy to the water. Don't forget to find the mass of your peanut/teddy before you burn it. This is from Science Dimensions 2 page 175.

Hey Tigger,

We used to do an experiment that boiled leaves, but it was mostly to do with determining the starch content of leaves. Then we either used variegated leaves, or covered some leaves with foil over half the leaf etc to look at production of sugars/starch in leaves. If that is what your teacher is talking about, then its not really determining the energy level of sugar per se, rather it tests the levels of sugar produced (energy conversion?) in leaves.

And yes, the burning tiny teddy experiment also works. I have even seen it done by an enthusiastic student, who made some biscuits with, and without sugar in the dough, and then compared the results. Pretty cool eh? Got just that bit closer to identifying the energy released by the sugar, but the subsequent maths was a nightmare

Thank you both so much for your help.
I too thought the boiling leaf was more to do with the starch but who am I to tell a teacher that. I will suggest the tiny teddy prac to them.

You can use marshmallows instead of tiny teddies but they are quite messy. Wonder whether you could use fairy floss as this is pretty much pure sugar? We normally use cheezels instead of peanuts here for measuring the energy content of food - they are easily stuck onto a pin set in plaster of paris before lighting and placing under a boiling tube.

We use fruit loops or nutrigrains.
Peanuts are banned in our school. Pasta is doable, but takes a long time to light and keep it going.
Lada

tigger wrote:I have been asked to look for a prac that will test the energy in sugar. I have tried various ways of typing in the question in google and here and have not found what the teacher is looking for.

It is all in knowing the right terms. Measuring the energy change in a reaction is called calorimetry, so the keywords you need are: "sugar calorimetry classroom experiment".

One of the top search results of this on google is the Soda Can Calorimeter: http://www.flinnsci.com/media/510570/soda_can.pdf

The PDF not only outlines the equipment setup, but explains the mathematics behind it.