Temperature Scales
Celsius, Fahrenheit and Kelvin measure temperature.
About this topic
Celsius sets 0 °C and 100 °C at water's freezing and boiling points, Fahrenheit uses 32 °F and 212 °F, and Kelvin starts from absolute zero. Conversions: K = °C + 273.15, and °F = 1.8 × °C + 32. A kelvin and a Celsius degree are the same size.
Science uses Kelvin because it is an absolute scale: 0 K is the lowest possible temperature, and temperatures in kelvin are proportional to the average kinetic energy of particles. Gas law calculations must use kelvin, because Celsius can be zero or negative while pressure and volume cannot.
Worked example: normal body temperature of 37 °C is 310 K, or 1.8 × 37 + 32 = 98.6 °F. A hot day of 95 °F is (95 − 32) / 1.8 = 35 °C. Room temperature of 20 °C is 293 K. Interestingly, −40 is the same in both Celsius and Fahrenheit.
Scales were invented from reference points that were easy to reproduce: Celsius from water, Fahrenheit from a brine mixture and body temperature. Most of the world uses Celsius for everyday life, while the United States uses Fahrenheit. A common error is to write degrees with kelvin; it is just K. Another is to double a temperature in Celsius and claim it is twice as hot, which is meaningless because the zero is arbitrary.
Key ideas
- K = °C + 273.15
- Absolute zero is 0 K
- Water freezes at 0 °C
Quick check
Use cases: where Temperature Scales helps
- Homework: review the key idea behind Temperature Scales before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Temperature Scales without notes.
- Visual learning: play with the interactive lab to see how Temperature Scales changes when you adjust its inputs.
- Teaching a friend: explain Temperature Scales in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Temperature Scales?
Celsius, Fahrenheit and Kelvin measure temperature.
What will I learn in Temperature Scales?
K = °C + 273.15. Absolute zero is 0 K. Water freezes at 0 °C.
Is Temperature Scales part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Temperature Scales lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Temperature Scales?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.