OT: Anybody here good with thermometers?

[Redwolf]

Well, not too off topic...this does involve something you put in your mouth!

My daughter's doing this science project in which she's supposed to determine whether an animal's fat layer really insulates it from the cold. The experiment calls for taking two bulb thermometers, sticking one in a cup full of shortening, and placing them both in the freezer, recording the starting temperature and then the temp at three-minute intervals for 1/2 hour.

OK...problem number one: Standard oral thermometers don't register any temperature at all unless the bulb is exposed to some kind of heat. So we each put one in our mouths until both registered 98.6, which we assumed would solve that problem.

Problem number two: Evidentally, they also won't register a drop in temperature. We had those suckers in the freezer for a solid half hour and neither dropped below the starting temp. Aparently the only way to get this kind of thermometer to drop is to shake it down.

Both I and our local pharmacist assumed that standard, old-fashioned oral thermometers were what was meant by "bulb-style thermometer," but maybe there's something else out there that we're not aware of? What we have clearly isn't working, and she only has a week to finish this experiment and a couple of related experiments involving thermometers. Thoughts?

Redwolf

[Nanohedron]

Cooking thermometers.

[Doug_Tipple]

As the laboratory supervisor for an aerospace manufacturing company, I used to do a lot a similar temperature recording with time. I used thermocouple sensors and a chart recorder. For your daughter's research, I would suggest any inexpensive outdoor bulb thermometer. They are designed to function right in the temperature range that your daughter wants to measure.

[Redwolf]

OK, next question...anybody have any idea where I can find a couple of those that aren't attached to decorative metal plates at about $20/per? The only place I've ever seen outdoor thermometers was at a hardware store, and those would be way too big to slip comfortably into the 9 ounce cups she's supposed to use.

I hate science fairs...they're nothing more than a lot of work and expense for the parents!

Redwolf

[FJohnSharp]

If you use two of those metal dial type of cooking thermometers--which I heartily recommend--make sure you look for that little dot in the middle of the stem. That's ground zero for the temp, and you ahve to make sure its well inside whatever you're measuring.

Those dial types are about $10 apiece at WalMart, and are very useful for the kitchen when the experiment is over. I'd also be that some friends already have some and you can borrow. But it would be a totally cool experimental constant to have identical thermometers.

[Redwolf]

I think hubby's come to the rescue. He found two identical outdoor thermometers at the drug store. They were encased in plastic, but he cut the plastic with a Dremel tool so they're small enough to fit in the cups.

Last year's experiment was so much simpler...all we had to do was watch apples rot! (she was testing to see which common variety of eating apple had the best keeping value. In case you're interested, the Pippin won hands down).

Redwolf

[Doug_Tipple]

Hello Redwolf,
I think that your husband has come on an acceptable solution. However, in rereading your description of the experiment, my thought is that you only really need one thermometer to do the experiment successfully. The temperature gradinet, with or without the shortening, can be done independently, thus requiring only one thermometer. In case the thermometers that you have don't work out, try this one on ebay. The price is right.
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 43883&rd=1

[Doug_Tipple]

I think that you should encourage your daughter as much as possible with regard to her interests in science. As a science major myself and a teacher of earth science, I think that science is very fascinating and might be an excellent career choice for your daughter. When I was her age, I was doing the same thing with the science fair projects. My dad was interested in science, and as a consequence all of his three sons have graduate degrees in science and have pursued careers in science, as well. I am the only one the plays flutes, however.

[Lambchop]

My daughter's doing this science project in which she's supposed to determine whether an animal's fat layer really insulates it from the cold. The experiment calls for taking two bulb thermometers, sticking one in a cup full of shortening, and placing them both in the freezer, recording the starting temperature and then the temp at three-minute intervals for 1/2 hour.

Right. Oral thermometers won't work. They're "special." A bulb thermometer simply has a reservoir of mercury or alcohol in a bulb at one end. The column itself is free to move up and down. A person-thermometer goes up only within a narrow range, but won't come down unless shaken.

Everyone gave excellent advice, to which I'll add another angle. Think about the animal with and without fat. You're wondering about the temperature of the inner animal, right? If you were able to stick a thermometer inside an actual animal, it would be measuring the temperature of animal innards. Both the fat animal and the skinny animal have the same innards.

In your school's recommended experiment, the thermometer in one container is in shortening. The other is in air? Is that the same "animal innards?" No. The results aren't going to be as meaningful as they would be if all circumstances were the same. Only the ONE variable should differ.

Another problem is that the thermometer in the air will be measuring the temperature of the cup itself unless you suspend it so that it doesn't touch anything. If it's in air, it's going to be affected rapidly by fluctuations in air temperature, i.e., the second you open the freezer door. You'll need to slow that down.

Usually, a thermometer in a lab refrigerator is suspended in a container of water. This keeps the temperature from fluctuating rapidly when you open the door to read the thermometer--you'll get a more reliable reading.

If you put both thermometers in a container of water (baby food jar?), suspended so that they don't touch the container itself, you'll have the same "animal innards" for both. Then, you can layer your shortening evenly around one jar.

You'll also have a problem with being unable to see the thermometer that is in the shortening. Taking it in and out will affect your experiment. My recommendation would be to use the kind of thermometer which employs a temperature sensor on a wire. Meat thermometers for the oven use these, as do outdoor thermometers which have indoor gauges. If you plan things right, you can do one half of the experiment at a time, rather than both together, so you need only one such thermometer which you can then use as part of an educational weather station. (Thinking ahead to next year's science project . . . ).

And, you know, shortening really isn't animal fat. Lard is closer. Animal fat has a microanatomic structure. It's encased in cells and stuff. If I were going to experiment with the insulating properties of body fat, I'd want to use . . . body fat.

Vegetarians might want to stop reading now.

The easiest way to do this is not with messy cups and shortening, but with cubes of beef and some beef fat which your butcher can supply.

Cut a beef chunk into a cylinder (so that the distance to the thermometer probe is even), place it on a rack, so that it isn't touching the sides of the freezer, insert the probe into the center, allow it to reach starting temperature and record your findings. You can run the wire right out the freezer door, so that you never need open the door or disturb your "hibernating experimental animal."

Next, simply wrap an even layer of beef fat around the cylinder, putting a bit on the bottom and a bit on the top (same depth). Punch a hole in the top for the probe and reinsert it into the same spot in the chunk.

Be sure to take photos and make diagrams of your experimental setup.

When you're done, put the suet outside in a tree for winter birds, toss the beef chunks into the stew, and install your new weather station thermometer.

[jbarter]

Well, not too off topic...this does involve something you put in your mouth!

Not necessarily.... sometimes thermometers get put where most people tell me to stick my whistles.