Science question

Question

Determine the number of calories needed to change 27g of water at 25C into steam at 100C(degrees celsius).

Answer 1

Hi Valerie,

 

The specific heat capacity of water is 1.00cal/g°C, this is the rate of heat energy water absorbs when its temperature is raised between 0 and 100°C. When water turns into steam at 100°C it absorbs heat at the rate 539 cal/g.

 

The  number of calories = energy needed to bring water to steam + energy needed to turn water into steam

                                    = mass*specific heat *change in temp + mass*latent heat of vaporization

                                    = 27g*1.00 cal/g°C *(100°C - 25°C) + 27g* 539cal/g

                                    = 2025+14553

                                    =16,578 calories or 16.6kcal