Calibrating a Thermometer

Apologia Chemistry  – What’s happening at my co-op.

Did you know that most thermometers are not accurate?  I had no idea.

In Module 2 we learned the boiling point of water measured in Fahrenheit is 212 degrees.  In Celsius it is 100 degrees.  The freezing point of water measured in Fahrenheit is 32 degrees, while in Celsius it is zero degrees.

This may not be a surprise to any of you and it certainly isn’t a surprise to me.  However; I have always had to ask someone what is the boiling point of water in Fahrenheit or Celsius, because I forget…until now.  It clicked.  I remember it.  I’m like Dorie in Finding Nemo.

Fahrenheit 212 boiling.  Fahrenheit 32 freezing.
Celsius 100 boiling.  Celsius 0 freezing.
Hey, I remembered.  Want me to say it again?  Ok…..

Please tell me that is something to be proud of.

Back to class!

Each student is given a thermometer (Celsius) they will be working with throughout the year.  To accurately calibrate the thermometers we have to find where the measurement stops at freezing.

We used crushed ice and cold water.  After a set amount of time, they take the temp.  If it is below zero, they are to add whatever to get to zero.  If it was above zero they are to subtract whatever to get to zero.  Any time the students use their thermometer they have to make adjustments on every measurement.

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You know, I don’t think the kids can get more excited.

Once the thermometer is calibrated, we set the beaker on a hot burner to start warming up the water.  They were to take the temp. every minute and hopefully get to boiling.

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Four students heated their waters, while one recorded their mesurement.  Since I could do this experiment at home, my daughter was the one to do the recording.

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Keep on stirring.  We never made it to boiling.  Hot plates and alcohol burners are not chemistry experiment friendly.  ug…..

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The students made a graph of the temperature to time.  What it should show, and it does here, is that the freezing point remains the same for a short time and then rises.  What it should also show, but doesn’t because we couldn’t get it to boil, is once it hits boiling at 100 C, the temp remains the same as long as it is a rolling boil.

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Once home, the daughter and I performed the same experiment.  We put the beaker right on the burner.  Oh, you noticed I have a beaker in my home.  Are you asking if I have Chemistry equipment in my home?  Why yes.  Yes, I do. I’ll post about all the Chemistry goodies I have later.

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When it is at a rolling boil, can’t be stirred down, the temp should read 100 degrees C.   My daughter’s thermometer calibrated at -1.  That means she has to add 1 to all of her measurements with this thermometer.

As you can see here, the temp stopped at 99 degrees.  Adding 1 makes it 100, where it should be.

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That, people, is calibrating a thermometer.🙂

4 responses to “Calibrating a Thermometer

  1. Well I just learned something new also. Thanks for sharing. ~Blessings~

  2. Thanks for your awesome website. You helped me to get through my first year teaching Biology last year! I also used several of your ideas for my Physical Science class.

    After several years of teaching a Chemistry, I finally just bought good old Coleman burners from the WalMart camping section. We use the wire mesh on the burner. The propane burns a lot hotter than any home science equipment we can get. I spent a lot on butane burners last year. That wasn’t great, but better than alcohol! The propane does require ventilation in the room, we we open the windows a bit. We got through the experiment in an hour this year, including the graphing.

    • Thanks Jennifer. My husband was going to get me propane, but the director of the co-op was not interested in it and we don’t have any windows to open in any of the rooms. I am taking extra days at my home, so hoping we can do a little more worth while experiments. It’s no fun if the experiments are so safe they don’t work. 🙂

  3. It is definitely something to be proud of!

    I appreciate this tutorial! We aren’t there yet, but anything I can do to add to my knowledge now is very helpful!

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