Question Video: Converting from Fahrenheit to Kelvin Physics • 9th Grade

What is 80° F in kelvin? Give your answer to the nearest kelvin.


Video Transcript

What is 80 degrees Fahrenheit in kelvin? Give your answer to the nearest kelvin.

To begin, we can recall that the kelvin is the base SI unit of temperature. So, oftentimes in physics, when we need to calculate with temperature, we have to convert values from any other temperature scale to the kelvin scale. Still though in some places, Fahrenheit is the most commonly used temperature scale, so it’s good practice to convert from Fahrenheit to kelvin. To do this, we can recall that a temperature in kelvin equals five-ninths times the temperature in Fahrenheit minus 32 all plus 273. And if this part of the formula looks familiar, it’s because this is precisely how we convert a value given in Fahrenheit to Celsius.

Remember, a change in temperature in kelvins has the same magnitude change in Celsius. So to convert Celsius to kelvin, we simply add 273. This is essentially what we’ll do to find the answer to this question. But let’s just go ahead and use this full formula written in green to do the conversion all in one go. Now, 𝑇 subscript 𝐹, the value that we’re starting with, equals 80 degrees Fahrenheit. So, let’s substitute this into the formula, and we have five-ninths times 80 degrees Fahrenheit minus 32 plus 273. Plugging this expression into a calculator gives a result of 299.6 recurring kelvin.

Finally, we’ve been told to round this to the nearest kelvin, so our answer just becomes 300 kelvin. Thus, we found that 80 degrees Fahrenheit is equivalent to 300 kelvin.

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