Summary: This set of activities introduces the importance of calibration to the students.
Preparation: The focus of this activity is to help the students think about different scales on tools that they use and how they know that they provide a true reading. It will also emphasize the benefits of using an electronic probe or sensor.
Materials:
unmarked thermometer (available
from Science Kit & Boreal Laboratories - thermometer blanks Catalog
Number 63351-00)
marked standard Celsius thermometer
temperature probe
boiling water
heating source and container suitable for boiling water
Styrofoam cups
ice water
water at varying temperatures (at least 250 ml per group)
small cork # 5 (for holding the unmarked thermometer)
nail (around 20 D in size)
fork (to hold the cork)
permanent fine point Sharpie markers (one for each group)
metric ruler
Classroom Management: This activity could be done as a teacher demonstration or by allowing the students "hands on" work in teams. The size of the teams will depend on the number of available thermometers and temperature probes.
Safety:
The unmarked thermometers
are made of glass. Care should be taken to not shatter or drop
them. Caution should be taken while placing the unmarked thermometers
in the one-hole stoppers so they do not break or shatter. Do
not use any thermometers with mercury.
Activity Steps:
Think About Scales
Ask the students to list different types of scales that exist. Possible types might include car speedometers, furnace (thermostat) dials, bathroom scales, and thermometers. Discuss with the students the following questions:
How do you know that a scale is giving a true reading?
If you were given an unmarked thermometer, could you design a method of using it to determine true temperature readings? Explain how.
To help make a scale on your unmarked thermometer, what two temperatures of water would provide you with two known values?
Why is the Celsius scale preferred in science to that of Fahrenheit?
Exploring Temperature Tools
Have the students place a marked thermometer, an unmarked thermometer, and a temperature probe in ice water. Using the marked thermometer as a reference, aske the students the temperature of the ice water? Have the students make a mark on the unmarked thermometer. Refer to the temperature probe manual to record the first temperature in the calibration program.
You should carefully place a marked thermometer, an unmarked thermometer, and a temperature probe in boiling water. This should be done as a demonstration for each group. Using the marked thermometer as a reference, ask the students the temperature of the boiling water? Make a mark on the unmarked thermometer for that temperature for the students. Refer to the temperature probe manual to record the second temperature in the calibration program.
Helpful Hint: Often times sophisticated equipment (ring stands, utility clamps, etc.) is not availblein primary classrooms. A fork can be used to place the unmarked thermometer in t he boiling water. Use the fork placed firmly placed in the cork to move the thermometer outside of the path of the steam (with the bulb of the thermometer still in the boiling water) to mark the boiling point. Care should be taken will placing the unmarked thermometer into the cork. If the fit is too tight, do not force the thermometer. It may shatter. Make the hole larger, but not so large that the thermometer will fall out of the cork.
Scaling the Temperature Tools
Now that the students have identified the boiling and freezing point of water on their unmarked thermometer, ask them how they could mark the other points between these two known points.
Remind the students that the Celsius scale is set to 100 equal divisions (degrees) between the freezing and boiling points. Ask the students if their unmarked thermometer present any difficulties in making accurate markings.
Since the unmarked thermometers are so small, marking each of these divisions will be impossible---no matter how thin the markings. The students should decide on how small the divisions can be an still maintain accuracy. Remember the divisions must be in units of 10. One strategy might be to measure the distance in millimeters with a metric ruler from the boiling point to the freezing point. Another might be to divide this distance by two and mark your 50-degree point. This should be used as an opportunity to discuss the notion of the limits of particular measurement instruments. Remind the students that the temperature probe automatically sets it scale from the two known points.
Have the students scale the unmarked thermometer as best as they can.
Collecting Data With Calibrated Tools
Provide the students with a wide variety of water at different temperatures in Styrofoam cups. Have the students test simulateanously the temperature of one of the cups of water with their newly marked thermometer, temperature probe, and scientific thermometer. Have them record the results from each tool. Have the students repeat the process for each cup.
Ask the students the following questions:
How did the temperature readings vary between tools?
How did the temperature readings vary from cup to cup?
Have the students write a paragraph that explains why scientific instruments need to be calibrated.
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