Science Buddies: "Ask an Expert"

Trying out the fat content in food experiment (Potato Chips). Dissolved the fat in acetone, filtered it and kept if outside overnight (24 hours). The weight lost in now dried food is less than fat that remained after the acetone evaporated. Say the Dried food jar was initially 100 gms, then after dissolving it is 90 gms. The fat remaining after drying (in a different Jar) the weight is 20 gms (i.e the extracted fat from chips). Where are we getting the extra 10 gms? It is consistent in all 10 -12 samples

Hi and welcome to Scibuddies.
I cannot say for certain why you got the results you did, but at least they are consistent, so whatever happened affected all the samples the same way.

The first thing you would think of is that somehow you read the scale wrong, but that is unlikely because you used a digital scale. Did you put all the strained out food bits back into the food jars?

The other source of error would be residual acetone that was weighed along with the samples, but if you followed the instructions (https://www.sciencebuddies.org/science- ... #procedure) then all the acetone would have evaporated.Obviously the total cannot be greater than the mass of the food that you started with. The acetone dissolves the fat so the food weighs less, but the weight of the remaining food plus the weight of the extracted fat can't be more than the weight of the food before extraction.

I have no explanation why you came up with higher weights. What I would do is try the extraction again being extra careful with the weighing and with allowing the acetone to evaporate completely. You don't have to do all three foods. Just pick one and do three extractions so that you have three readings to compare.

If you still get the same results, then that is the way you have to present your data. There is an explanation. I just don't know what it is.

Let us know what happens when you repeat the experiment. In fact, it would be a good idea to make a data table and send that in the post so we can see your actual results. Maybe something will click in someone's mind that gives the answer.

Sybee

Thanks. Will share the result. Is it possible that there might be impurities in the acetone?

You're welcome!

Impurities in the acetone? Probably a little--but not that much. Do an experiment. Weigh a jar, add 20 ml acetone, weigh again and let it all evaporate and then weigh again. That is one control that you should have done in your experiment anyway. It will answer your question about the impurities and rule out one more possibility.

Keep us posted on what you find out. Remember--just because an experiment turns out weird, that's no reason to ignore the data. Lots of scientists have made discoveries by accident.

Sybee