How do I calculate the total amount of energy required to change 125g of ice at -25 degrees Celsius to 125g of steam at 150 degrees Celsius?

That 's a physics Question. Anyway, you need to have the specific latent heat of fusion and the specific latent heat of vaporisation plus the specific heat capacity of water in all of its three forms (ie solid, liquid and gas).

1) You then multiply the specific heat capacity of ice for the 125g of ice for each degree rise, that is by 25.
2)At 0 Celsius, you'll use the spec latent heat of fusion for the 125g of ice.
3)From 0 to 100 Celsius multiply the spec heat cap of water in liquid state by the raise in temperature, that is by 100.
4)At 100, you'll use the spec latent heat of vaporisation for the 125g of liquid water.
5)From 100 to 150 Celsius, multiply the spec heat cap of steam by the raise in temp, that is by 50
6) Finally, add the answers from 1) to 5) to have the total energy you used.

I don't remember the values you need but they must have been given to you. Hope it helped.