Question

How much energy is required to change a 60 g ice cube from ice at -25

Answer 1

1. Heating ice
How much heat would be required to raise 60g of ice to its melting point?
The ice temperature must be raised 25 degrees to reach 0oC.

Since the specific heat of ice is 0.50 cal/g-oC, that means that 0.50 calories is needed to raise 1g of ice 1oC. Thus, it would take 60 x 0.50 calories to raise 60g up 1oC and25 x 60 x 0.50 =750 cal to raise the ice to its melting point.

2. Melting ice
How much heat would be required to melt the 60g of ice?
The latent heat for melting ice is 80 cal/g. That means that 1g of ice requires 80 cal of heat to melt.

Thus, 60g requires 60 x 80 = 4800 cal to melt.

3. Heating water
How much heat is required to heat 60g of water from 0oC to its boiling point of 100oC?
Since the specific heat of water is 1.00 cal/g-oC, that means that 1.00 calorie is needed to raise 1g of water 1oC. Thus, it would take 60 x 1.00 calories to raise 60g up 1oC and 100 x 60 x 1.00 = 6000 cal to raise the water to its boiling point.

4. Boiling water
How much heat would be required to boil the 60g of water?
The latent heat for boiling water is 540 cal/g. That means that 1g of water requires 540 cal of heat to boil.

Thus, 60g requires 60 x 540 = 32400 cal to boil.

5. Heating steam
How much heat is required to heat 60g of steam from 100oC to 105oC?
Since the specific heat of steam is 0.48 cal/g-oC, that means that 0.48 calories are needed to raise 1g up 1oC. Thus, it would take 60 x 0.48 calories to raise 60g of steam 1oC and 5 x 60 x 0.48 = 144 cal to raise the temperature of the steam to 105oC.

6. Total
The total heat required to change 60g of ice at -25oC to steam at 105oC is:

750 + 4800 + 6000 + 32400 + 144 = 44094 cal.

1 calorie = 4.18400 joules

4.184 x 44094 = 184,489.29 joules