Posted by Linda on Tuesday, March 18, 2014 at 11:02pm.
1000 J = 1 kJ is the factor so
220 J x (1 kJ/1000 J) = ?
You see you multiply the value you start with by the factor. You can place the factor as 1000/1 or as 1/1000. Only one way is right. The right way will ALWAYS cancel the unit you don't want and keep the unit you want. For example, you see J in the numerator cancels J in the denominator and kJ in the numerator (the unit you want to keep) stays.
Next is 350 kJ to cal.
1000J = 1 kJ and
4.184 J = 1 cal. Here there are two factors but they work the same way even in long lines of factors from one unit to the next.
350 kJ x (1000 J/1 kJ) x (1 cal/4.184 J) = ? cal
You see the first kJ in the numerator cancels with the first kJ in the denominator of the first factor. That factor converts kJ to J. The J in the first factor in the numerator cancels with J in the denominator of the second factor. That factor converts J to cal which is what you want.
For the others:
1000 cal = 1 kcal
1 cal = 4.184 J
1000 cal = 1 kcal.