Question

Which of the following transitions will require the most thermal energy?

a)1 g of ice at –15 °C to 1 g of ice at –5 °C
b)1 g of ice at –5 °C to 1 g of water at 5 °C
c)1 g of water at 5 °C to 1 g of water at 15 °C
d)1 g of water at 15 °C to 1 g of water at 25 °C

Answer 1

Here, 1 g of ice at –5 °C to 1 g of water at 5 °C will require the most thermal energy 'cause it will require some extra energy (latent heat = 80 Cal/gm for this case) for changing the phase from 0 C ice to 0 C water.

In short, Your Answer would be Option B

Hope this helps!