Temperature and Temperature Scales in GOB Chemistry

Chapter 3: Matter and Energy 3.4

Temperature: Definition and Measurement

Temperature is a fundamental concept in chemistry, representing the degree of hotness or coldness of an object relative to another. It is a key physical property measured using thermometers and is essential for understanding chemical and biological processes.

• Temperature is a measure of how hot or cold an object is compared to another object.

• It is measured using a thermometer.

• Common applications include measuring body temperature to assess health status (e.g., fever, hypothermia).

• Example: A digital ear thermometer is used to measure body temperature in medical settings.

Temperature Scales

There are three main temperature scales used in chemistry: Fahrenheit (°F), Celsius (°C), and Kelvin (K). Each scale has its own reference points and units.

• Fahrenheit (°F): Used primarily in the United States. The freezing point of water is 32°F, and the boiling point is 212°F.

• Celsius (°C): Used worldwide and in scientific contexts. The freezing point of water is 0°C, and the boiling point is 100°C.

• Kelvin (K): The SI unit for temperature, used in scientific calculations. The freezing point of water is 273 K, and the boiling point is 373 K. Kelvin does not use the degree symbol and does not have negative values.

• Each scale divides the temperature difference between boiling and freezing points of water into units called degrees.

Comparison of Temperature Scales

The following table summarizes the key reference points for each scale:

Scale	Freezing Point of Water	Boiling Point of Water	Units Between Points
Fahrenheit (°F)	32°F	212°F	180
Celsius (°C)	0°C	100°C	100
Kelvin (K)	273 K	373 K	100

Kelvin Temperature Scale

The Kelvin scale is based on absolute zero, the lowest possible temperature where molecular motion ceases. It is widely used in scientific calculations.

• Absolute zero is defined as -273°C or 0 K.

• Kelvin units are called kelvins (K) and do not use the degree symbol.

• There are no negative temperatures on the Kelvin scale.

• The size of one kelvin is equal to one degree Celsius: $1~K = 1~^ ext{o}C$.

Converting Between Temperature Scales

Temperature conversions are essential for scientific work. The following equations allow conversion between Celsius, Fahrenheit, and Kelvin.

• Celsius to Fahrenheit: $T_F = 1.8T_C + 32$

• Fahrenheit to Celsius: $T_C = \frac{T_F - 32}{1.8}$

• Celsius to Kelvin: $T_K = T_C + 273$

• Kelvin to Celsius: $T_C = T_K - 273$

Example: Convert 34.8°C (body temperature in hypothermia) to Fahrenheit:

• Given: $T_C = 34.8$

• Use: $T_F = 1.8T_C + 32$

• Calculation: $T_F = 1.8 \times 34.8 + 32 = 62.6 + 32 = 94.6~^ ext{o}F$

Practice Problems (Learning Checks)

• What is the temperature at which water freezes?

  • 32°F

  • 0°C

  • 273 K

• What is the temperature at which water boils?

  • 212°F

  • 100°C

  • 373 K

• How many Celsius units are between the boiling and freezing points of water?

  • 100

• Convert -15°F to Celsius:

  • Use $T_C = \frac{-15 - 32}{1.8} = \frac{-47}{1.8} \approx -26.1~^ ext{o}C$

• Convert 37°C (normal body temperature) to Kelvin:

  • Use $T_K = 37 + 273 = 310~K$

Summary Table: Temperature Scale Reference Points

Event	Fahrenheit (°F)	Celsius (°C)	Kelvin (K)
Freezing Point of Water	32	0	273
Boiling Point of Water	212	100	373
Normal Body Temperature	98.6	37	310
Absolute Zero	-459	-273	0

Additional info: The notes are based on "General, Organic, and Biological Chemistry: Structures of Life" by Timberlake, Chapter 3, and are relevant for GOB Chemistry students studying matter, energy, and temperature scales.