An 800. mL sample of oxygen at 90.00C and was cooled at constant pressure until it has a volume of 400.0 mL. What was the final Celsius temperature of this gas?

In a heat engine of 1000 j of heat enters the system and the piston does 500 j of work what is the final internal energy of the system if the inital energy was 2000 j we have to do all of these down here 1)write the equation 2)list out your know variables 3)plug the numbers into the equations 4)solve 5)write your solution statemtn that includes inital energuy and final energuy added