Changes of State ice to steam problem

In summary, the problem is asking for the energy needed to convert 0.500 kg of ice at -20C to steam at 250 C. Using the specific heat capacities and heat of fusion and vaporization, the energy in each phase is calculated. The next step is to use the Clausius-Clapeyron equation to find the energy needed for the phase changes. Finally, the total energy needed can be obtained by adding all the energy values together.
  • #1
jKotha
30
0
Ok, I am having some trouble with this problem:

How much energy does it take to convert .500 kg ice at -20C to steam at 250 C? Specific heat capacities: ice: 2.1 j/g C, liquid: 4.2 j/g C, steam: 2.0 j/g C. Hvap = 40.7 kj/mol, and Hfus = 6.02 Kj/mol.


What I have done so far is use q=mst for all 3 phases to obtain the energy in 3 phases.

q= (.500)(2.1)(20) = 21000 J, this is for the ice from -20C to 0C
q= (.500)(4.2)(100) = 210000 J, this is from 0 C to 100 C because of liquid water to boiling pt (steam).
q= (.500)(2.0)(150) = 150000 J, this is from 100C to 250C

Am I on the right track? Or am I doing this all wrong? I don't have a clue what to do next. However I think it must use the Clausius-Clapeyron equation in some context. I'm not sure what to do with the Hfus either. Please HELP!

Thanks,
Jkotha
 
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  • #2
One also has to account for the heat of fusion (ice absorbs energy (heat) at constant temperature while changing to liquid) and heat of vaporization (steam condenses (by releasing heat) to liquid at constant temperature).
 
  • #3
I Got It!

Hey, thanks. YOU ARE THE MAN. I can't believe I forgot about those.
 

What is the process of changing ice to steam?

The process of changing ice to steam is called phase transition or change of state. It involves the absorption of energy in the form of heat, causing the ice molecules to gain enough energy to break free from their fixed positions and become liquid. As more heat is added, the liquid molecules gain more energy and eventually break free into the gas phase, becoming steam.

What is the required energy for ice to steam phase transition?

The required energy for ice to steam phase transition is known as the latent heat of vaporization. This is the amount of heat energy needed to change a substance from liquid to gas at its boiling point. For water, the latent heat of vaporization is 2260 kJ/kg.

Why does ice melt before turning into steam?

Ice melts before turning into steam because it needs to absorb enough energy to break the bonds holding the ice molecules together and become liquid. This is a slower process compared to the change from liquid to gas, as the molecules in the liquid phase have more energy and are able to move more freely.

What factors affect the rate of ice to steam phase transition?

The rate of ice to steam phase transition is affected by several factors, including temperature, pressure, and surface area. Higher temperatures and lower pressures will speed up the process, while a larger surface area of the substance will allow for more heat to be absorbed and result in a quicker phase transition.

Is the phase transition from ice to steam reversible?

Yes, the phase transition from ice to steam is reversible. This means that if the steam is cooled down, it will turn back into liquid and then solidify into ice. This is because the molecules in the gas phase lose energy and are able to bond together again in the liquid phase. However, this process is not always 100% reversible and some energy may be lost in the form of heat.

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