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# Thermometers: Old and New (page 2)

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Author: Janice VanCleave

1. Make another gas thermometer by standing a straw with a 71/32-inch (O.56-cm) diameter in a cup half filled with water tinted with food coloring. While the straw is in the water, place your index finger over the open end of the straw. Hold the straw closed with your finger while lifting the straw out of the colored water and inserting the free end into an empty soda bottle. Seal the mouth of the bottle by wrapping clay around the straw. Observe how the colored plug of water rises and lowers in the straw as the air in the bottle is heated and cooled.
2. In 1623, a French physician, Jean Rey, designed a liquid thermometer. This instrument worked because liquids, like gases, expand and contract when heated. Construct a model of the Rey thermometer by filling a glass soda bottle with water tinted with food coloring. Insert about 2 inches (5 cm) of the end of a drinking straw into the bottle of colored water. Seal the mouth of the bottle by wrapping clay around the straw. Stand the bottle in a bowl of warm water.
1. Galileo's and Rey's thermometers had no fixed scale. The first thermometer scale was suggested by Christian Huygens (1629-1695), a Dutch mathematician, astronomer, and physicist. He used only one fixed point (either the freezing or the boiling point of water). In 1714, Gabriel Fahrenheit, a German scientist, introduced a simple mercury thermometer with a scale. Add a scale to your Rey thermometer model by attaching a piece of stiff paper to the straw with tape. Measure the temperature of the water in order to mark the Rey scale. (See Figure 29.3.) Try different straw and/or tube sizes.
2. What effect does atmospheric pressure have on the accuracy of open thermometers? Repeat the original experiment using the Rey thermometer with its scale and/or add a scale to the Galileo thermometer. Measure the atmospheric pressure with a barometer or secure the information from a television or radio weather forecast Take measurements on different days with varying atmospheric pressures. Display a chart of the results.
3. Draw diagrams comparing the Fahrenheit, Celsius, and Kelvin thermometer scales. Use the following algebraic equations to compute temperatures for each of the three scales. See Appendix 13 for example calculations.
1. Relationship between Fahrenheit and Celsius:
2. Relationship between Celsius and Kelvin

Display the diagrams and a few computations. Indicate common and interesting temperatures such as the average person's body temperature of 98.6°F, the boiling point of water at 100°C, and the freezing point of water at 273 K

### Get the Facts

The Italian physicist Galileo's thermoscope is the first known instrument used to measure temperature. Find out more about the development and uses of thermometers. What did the thermoscope look like? How was the Florentine thermometer different from the Rey liquid thermometer? Who introduced the first mercury thermometer? What was used to determine the first thermometer scales? Include information about the thermometer introduced by Gabriel D. Fahrenheit, Anders Celsius, and Lord Kelvin. F"md out about the use of digital thermometers and heat-sensitive "chameleon" chemicals that change colors.

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