How much energy is needed to change 70g of ice at 0ºC to water at 90°C?

The energy needed to change 70 g of ice to water is aprrox. 50 kJ.

Explanation:

As the problem is to derive the energy required to melt the ice to water, first we have to determine the latent heat of ice. Latent heat of ice is also termed as latent heat of fusion. It is the amount of energy stored in the molecules in order to form ice from water. So, generally 1 g of ice will have 334 J of energy in them.

Then, 70 g of ice will contain 70 * 334 J = 23380 J=23.38 kJ of latent heat of fusion.

So, this energy is used to convert ice to water. Another energy is required to increase the temperature of water to 90°C from 0°C. This is derived using the specific heat formula.

Q = mass*specific heat of water*change in temperature

Mass is given as 70 g, specific heat of water is 4.186 J/g and the change in temperature will be (90-0) = 90°C

Then, Q = 70*4.186*90=26372 J=26.4 kJ

So, the total energy needed is 26.4 + 23.4 = 49.8 kJ.

Thus, the energy needed to change 70 g of ice to water is aprrox. 50 kJ.