Units of temperature tell us exactly how hot 🔥 or cold 🥶 something is.
There are three units of temperature, also called temperature scales, used in the world:
Celsius, Fahrenheit, and Kelvin.
Units of temperature are exact temperature changes everyone agrees on.
Only Celsius and Fahrenheit are commonly used every day.
Kelvin is used by scientists to measure the coldest things in the universe. You'll learn more about Kelvin later.
The Celsius scale is used in most countries around the world, except for the United States.
Celsius is based on the temperature at which water boils and freezes.
The unit of temperature in the Celsius scale is degrees Celsius. Its abbreviation is °C.
Water freezes at 0 °C.
Tip: Ice also melts at above 0 °C.
0 °C is the temperature where water changes state between liquid and solid.
Water boils at 100 °C.
On a nice day outside, it might be 23 °C.
Tip: Some people put a space before or after the degree symbol, or put no space at all:
23 °C
23°C
23° C
All three ways are acceptable. Just ask your teacher which they prefer and be consistent. The first way above, 23 °C, is used most in business writing.
Now, let's learn about the Fahrenheit scale.
The Fahrenheit scale is used in the United States.
The unit of temperature in this scale is the degree Fahrenheit. Its abbreviation is °F.
Water freezes at exactly 32 °F.
Water boils at 212 °F.
On a nice day, it might be 72 °F outside.
In the 1700s, more than three hundred years ago, a German physicist name Daniel Gabriel Fahrenheit invented the first temperature scale.
He simply decided that the temperature of salty, icy water had a value of 30°, and that the average human body temperature had a value of 90°.
Later, scientists found out that the freezing point of water was actually 32 °F, and the average human body temperature actually had a value of 98.6 °F.
You can always convert from Celsius to Fahrenheit and back.
0 °C = 32 °F
Freezing temperature
23 °C = 72 °F
Nice day
100 °C = 212 °F
Boiling water (very hot)
A thermometer is an instrument used to measure temperature.
The type that is most commonly used in households is a narrow glass column filled with red liquid.
The level of the liquid goes up as it gets hotter. It goes down as it gets colder.
There are also digital thermometers.
In this type of thermometer, you can just read the temperature as a plain number.
To read the temperature on a thermometer, look at the top of the red liquid.
What's the temperature in °C?
That's right! It's 40 °C. ✅
What's the temperature in °F?
Yes, it's 104 °F. ✅
That's quite hot. You'd be sweating outside.
Your body temperature is about 98 °F, or 37 °C
A hot cup of cocoa is 150.8 °F or 66 °C.
A very cold bottle of water is 35.6 °F or 2 °C.
Warm bread is 125.6 °F or 52 °C.
A just cooked grilled cheese sandwich is 138 °F or 58.9 °C
The inside of a hot oven is 300 °F or 149 °C. That's hotter than the boiling temperature of water.
Inside the classroom is 68 °F or 20 °C.
Knowing the temperature in a place helps us prepare well.
Unfortunately, converting between the two scales isn't very easy. It takes a few steps.
1️⃣ First, subtract 32 from the temperature in Fahrenheit.
2️⃣ Then, divide the answer you get by 1.8. 🙈
°C = (°F - 32) ÷ 1.8
Let's try converting 53.6 °F to Celsius.
(53.6 - 32) ÷1.8 = ?
21.6 ÷ 1.8 = 12
53.6 °F is equal to 12 °C.
1️⃣ First, multiply the temperature in Celsius by 1.8 or 9/5.
2️⃣ Then add 32.
°F = (1.8 × °C) + 32
Let's try to convert 36 °C to °F.
(1.8 × 36) + 32 = ?
64.8 + 32 = 96.8
36 °C is equal to 96.8 °F.
Excellent job learning about units of temperature.
Now, try the practice.