Not so very easy.?...and Celsius maybe?

Sorry.i thought it said it was very easy,my mistake I think.

Kelvin and Celius (sic) can be swapped with Farenheit (sic), without changing the description of either group. Therefore the puzzle is not unique, and ignores one of the rules of this game.
Also,
Can't understand either why people take the time and effort to create a puzzle for members of the public to attempt, and then ruin them with multiple typos???
Celius isn't even phonetically correct, and the proper meaning cannot even be inferred by reading.
As a result, people are inclined to look for hidden words, or anagrams.
It's just cheap & lazy.

A low-quality grid: misspellings, two categories of the fill-the-blank form (best only to have one), questionable categorization, and closely overlapping categories. Avoid.

Compared to a lot of grids lately this is not bad. At least it seems to be a genuine attempt and has some entertaining parts.

Agree with the others, overall a poor grid.

Learn to spell

Need to chill out, this is over two years old and is still on the good page despite the comments.