When you want to know how tall you are, you use a ruler to measure your height. The scale that is used to measure height is in feet or meters. If you want to know how much you weigh, a scale is used in pounds or kilograms. We need a "scale" to measure amounts of a specific desired quantity.

When you stand on the bathroom scale, do you accept its reading as true? How do you know that the scale on your furnace or air conditioning thermostat is registering the correct value? You use scales everyday. A true scientific instrument needs to be tested and registered at two known values to provide you with an accurate reading.

Think about your earlier class discussion about the temperature scale. Discuss with your group your ideas for determining the accuracy of your three measuring tools. This process is known as calibration.

Go to "Investigating the Question" to see how to calibrate your thermometer.