A ammonia as it has the least molar mass
        
             
        
        
        
<span>Oceanic-oceanic convergent plate boundary. 2 Continental convergent plate boundary. 3 Oceanic-continental convergent plate boundary.</span>
        
             
        
        
        
 It depends, for example, it is quite important to know the Kelvin scale (i.e 0 degrees Celsius is 273 K and -273 degrees Celsius is 0 K ) when dealing gases. But I don't know other situations where you would need to know other temperature scales.
Hope this helps and also if you are using Fahrenheit 1 Fahrenheit is -17.22 degrees Celsius