Question

Duncan knows that it takes 36400 cal of energy to heat a pint of water from room temperature to boiling. however, duncan has prepared ramen noodles so many times he does not need to measure the water carefully. if he happens to heat 0.700 pint of room-temperature water, how many kilojoules of heat energy will have been absorbed by the water at the moment it begins to boil?

Answer 1

1 cal = 4.184 joules 

Therefore, 30940 cal = (30940 * 4.184) joules = 129000 joules (to 3.s.f) = 129kJ (3.s.f) 

Therefore, 0.850 pints require 129kJ (3.s.f) to boil from rtp. 

Hope this helps!