Measuring Temperature
A thermometer is an instrument that measures temperature, or how hot an object is. The How It Works box on page 21 describes how a bulb thermometer measures temperature.
The two temperature scales that you are probably most familiar with are the Fahrenheit scale and the Celsius scale. On the Fahrenheit scale, water freezes at 32°F and boils at 212°F at sea level. On the Celsius (or centigrade) scale, water freezes at 0°C and boils at 100°C. A degree Celsius is almost twice as large as a degree Fahrenheit. There is also a difference of 32 degrees between the zero point of the Celsius scale and the zero point of the Fahrenheit scale. You can convert from one scale to the other by using one of the following formulas.
The SI base unit for temperature is the kelvin (K). A temperature of 0 K, or 0 kelvin, refers to the lowest possible temperature that can be reached. In degrees Celsius, this temperature is −273.15°C. To convert between kelvins and degrees Celsius, use the following formula.
Figure 19 compares some common temperatures expressed in degrees Celsius, degrees Fahrenheit, and kelvins.
Section 1.3 Assessment
Reviewing Concepts
Why do scientists use scientific notation?- What system of units do scientists use for measurements?
- How does the precision of measurements affect the precision of scientific calculations?
List the SI units for mass, length, and temperature.
Critical Thinking
Applying Concepts A bulb thermometer gives an indoor temperature reading of 21°C. A digital thermometer in the same room gives a reading of 20.7°C. Which device is more precise? Explain.
Calculating Convert −11°F into degreesCelsius, and then into kelvins.
Math Practice
Write the following measurements in scientific notation. Then convert each measurement into SI base units.
0.0000000000372 g
45,000,000,000 km
The liquid in a bulb thermometer falls 1.1 cm. Calculate the liquid's change in volume if the inner radius of the tube is cm.
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