Degrees Celsius: Definition & Conversion

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  • 0:02 Definition
  • 0:45 Temperature Conversions
  • 2:09 Fahrenheit to Celsius
  • 7:42 Lesson Summary
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Lesson Transcript
Instructor: Elena Cox
Temperature refers to how hot or cold something is. The same temperature has different readings on the three temperature scales shown below - Fahrenheit, Celsius, and Kelvin. Learn more about the Celsius temperature scale, practice conversion among different scales, and test your knowledge with quiz questions.

Definition of Celsius

In science, the Celsius scale is used more often than the Fahrenheit scale. The Celsius scale is divided into 100 equal parts, called degrees Celsius (°C), between the freezing point and boiling point of water. This scale was invented by Anders Celsius in 1742. Celsius also based his scale on the freezing and boiling points of water. The freezing point of water on this scale is 0 degrees Celsius (0°C). The boiling point of water is 100 degrees Celsius (100°C). This thermometer scale is sometimes called the centigrade scale because there are 100 Celsius degrees between the two fixed points.

Temperature Conversions

As shown by these thermometers, a given temperature is represented by different numbers on the three temperature scales:

Temperature Scales
comparing f c and k

For example, the freezing point of water is 32°F, 0°C, or 273 degrees Kelvin. As you can see, 0°C is actually a much higher temperature than 0 K, but a change of 1 degree Kelvin is equal to a change of one Celsius degree. In addition, 0°C is a higher temperature than 0°F, but a change of one Fahrenheit degree is not equal to a change of one Celsius degree. We can convert from one scale to another using these simple equations.

Conversion Equations
conversion table

Let's look at some examples on how to use the conversion table. A weather report of 21°C in London, England, predicts a pleasant day, good for shorts and a T-shirt. A weather report of 21°F in Minneapolis, Minnesota, means a heavy winter coat, gloves, and a hat will be needed. Because the U.S. is only one of a few countries that use the Fahrenheit scale, it is useful to know how to convert between Fahrenheit and Celsius.

  • T(Fahrenheit) = 9/5 T(Celsius) + 32
  • T(Celsius) = 5/9( T(Fahrenheit) - 32)

k to c con

Fahrenheit to Celsius Conversions

Let's look at the examples of major conversions between various temperature scales.

A friend in Paris sends you a recipe for a cake. The French recipe says to bake the cake at a temperature of 200°C for 45 minutes. At what temperature should you set your oven, which uses the Fahrenheit scale?

Let's break this question down.

1. You're looking for: the temperature in degrees Fahrenheit

2. You're given: the temperature in degrees Celsius

3. Relationships: Use the conversion formula: T(F) = 9/5 T(C) + 32

4. Solution: T(F) = (9/5)(200) + 32 = 392°F

The scale that is still used in modern scientific work (although it is gradually being replaced) is associated with the name of a man who neither first proposed it nor ever actually produced it. Anders Celsius (1742) used the freezing and boiling point of water for reference points and then divided the distance between them into 100 equal parts: a convenient scheme for the user. Strangely enough, Celsius set the temperature of freezing water at 100° and boiling at 0°. Some years later, with these two numbers more reasonably interchanged, the arrangement came to be known as the centigrade scale (from the Latin centum, meaning 100, and gradus, meaning degree). The tenth International Conference on Weights and Measures (in 1954) changed the scale's name to the Celsius scale.

Celsius and Kelvin Scales
k and c scales

Let's solve more problems on conversions between Celsius and Fahrenheit temperature scales.

Let's say you are planning a trip to Iceland where the average July temperature is 11.2°C. What is the temperature in Fahrenheit?

1. You're looking for: the temperature in degrees Fahrenheit

2. You're given: the temperature in degrees Celsius.

3. Relationships: Use the conversion formula: T(F) = 9/5 T(C) + 32

4. Solution: T(F) = (9/5)(11.2) + 32 = 52.2°F

Here's another example: you are doing a science experiment with a Fahrenheit thermometer. Your data must be in degrees Celsius. If you measure a temperature of 125°F, what is this temperature in degrees Celsius?

1. You're looking for: the temperature in degrees Celsius

2. You're given: the temperature in degrees Fahrenheit

3. Relationships: Use the conversion formula: T(C) = 5/9(T(F) - 32)

4. Solution: T(C) = (5/9)(125 - 32) = 51.7°C

Here's a final, two-part example. The temperature on the Moon varies from -230°C at night to 120°C during the day. What is the range in temperature on the Moon in degrees Fahrenheit?

First, you will have to convert -230°C into degrees Fahrenheit:

1. You're looking for: the temperature in degrees Fahrenheit

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