4C.11

[Raashi Chaudhari 3B]

Hi!
I am a bit lost about what to do for this problem and am unable to make sense of the solutions as well.
The problem asks, "How much heat is needed to convert 80.0 g of ice at 0 C into liquid water at 20 C"
I understand that there's a phase change occurring and the state is going from solid to liquid, but I don't know what to do with that information.
Hope someone can help!

[Katie_Dinh_1D]

Hello!
1) I calculated the amount of energy needed to melt 80.0g at 0.00 C of ice using the known delta h of fusion. We convert the grams of ice into moles and multiply by deltaHfusion. This will convert our ice to liquid
2) From here, we now have liquid water at 0.00 C, so we need to calculate the energy needed to raise the temperature from 0.00 to 20.00 C. We can calculate this using q=mCdeltaT
3)we can just add the values we got from both steps to get the final answer. Hope this helps!

[annabelchen2a]

Hi! For problems like these, one of the UA's (I can't remember which one) said it would be helpful to draw a heating curve, so you know when to implement multiple steps or just one. So for this problem, you would need to melt the 80.0 grams of ice at 0°C (step 1) and then heat the liquid water to 20°C (step 2).
Just keep in mind step 1 requires enthalpy of fusion for water, which is 6.01 Kj/mol, and step 2 requires the equation q = mcΔT.

[Kayla Law 2D]

Hi! You have to break this problem up into multiple steps. First, you need to calculate the amount of heat needed for a phase change for 80.0 g of ice into 80.0 g of liquid water. To calculate the amount of heat required for a phase change, you can use the equation q = nΔH, where n is the number of moles. So, for this problem, the heat of the phase change is q = (80/18.01)*ΔHfusion since the ΔH of fusion is the enthalpy of fusion, or the amount of heat required to change one mole of a substance from a solid to a liquid. Next, your liquid will be at 0°C and the question asks how much heat is needed to convert the ice into liquid water at 20°C, so you need to calculate the amount of heat needed to raise the temperature of the water by 20°C. Therefore, you can use the equation q = mCΔT, where m is the mass of the water, C is the specific heat capacity of liquid water, and ΔT is the change in temperature. Finally, you just add the heat needed for the phase change and the heat needed to raise the temp of the liquid water. Hope this helps! :)