What is the total energy required to change 15 g of ice at - 20°C to water at 100°C?

To change ice of - 20°C to water of 100°C you will need energy of 7524 J.

Explanation:

let q be the heat energy required for that given temperature change, c = 4.18 J/g.°C be the specific heat of water and ΔT be the change in temperature.

then:

the amount of energy required to change ice of temperature - 20°C to water at 100°C is:

q = m*c*ΔT

= (15) * (4.18) * (100 - (-20))

= 7524 J

Therefore, to change ice of - 20°C to water of 100°C you will need energy of 7524 J.