Moment the ice completely melts?

In summary, the water's entropy decreases by 190 due to the heat of fusion of the ice, and the entropy of the water remains unchanged when the ice melts.
  • #1
~angel~
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Please help.

In a well-insulated calorimeter, 1.0 kg of water at 20C is mixed with 1.0g of ice at 0C. What is the net change in entropy of the system by the moment the ice completely melts? The heat of fusion of ice is 3.34*10^5 J/kg.

I'm not sure how to do this problem. I thought that since it is 1kg of water, change in entropy for that is -4190/293K. I also though that for the ice, it would be (0.001*3.34*10^5)/273 as well as 4190/273 when it melts.

Thank you.
 
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  • #2
~angel~ said:
Please help.

In a well-insulated calorimeter, 1.0 kg of water at 20C is mixed with 1.0g of ice at 0C. What is the net change in entropy of the system by the moment the ice completely melts? The heat of fusion of ice is 3.34*10^5 J/kg.

I'm not sure how to do this problem. I thought that since it is 1kg of water, change in entropy for that is -4190/293K. I also though that for the ice, it would be (0.001*3.34*10^5)/273 as well as 4190/273 when it melts.
The change in entropy of the water is:

[tex]\Delta S_{water} = \Delta Q/T_{water}[/tex]

where [itex]\Delta Q[/itex] is the heat loss, which is the same as the heat gained by the ice.

AM
 
  • #3
Would Q for water just be -4190, or is there something else involved?
I'm also not sure about the ice.
 
  • #4
You've already calculated the change of Q of the ice (0.001*3.34*10^5). So the change in entropy of the ice is just (0.001*3.34*10^5)/273, which you've done.
Regarding the change in entropy of the water, the change in Q is just the negative of the Q gained by the ice i.e. it would be -(0.001*3.34*10^5). So the change in entropy of the water is just -(0.001*3.34*10^5)/293. So now you can calculate the net change in entropy by just adding them up :)
Hope you understood that, I'm horrible at explaining things
 
  • #5
Yeah, thank you =)
 

Related to Moment the ice completely melts?

1. What happens to the temperature when ice completely melts?

When ice completely melts, the temperature remains constant at 0 degrees Celsius (32 degrees Fahrenheit) until all the ice has melted. This is because the energy is being used to break the bonds between the solid water molecules, rather than increasing the temperature.

2. Does the melting point of ice change?

The melting point of ice, which is 0 degrees Celsius (32 degrees Fahrenheit), does not change when the ice completely melts. This temperature remains constant as long as the ice and water are in equilibrium.

3. Why does ice melt when it comes in contact with something warm?

Ice melts when it comes in contact with something warm because heat energy is transferred from the warm object to the ice. This causes the ice molecules to gain enough energy to break their bonds and turn into liquid water.

4. How long does it take for ice to completely melt?

The time it takes for ice to completely melt depends on various factors such as the temperature of the surrounding environment, the size and shape of the ice, and the material it is in contact with. Generally, it can take anywhere from a few minutes to a few hours for ice to completely melt.

5. Does water always have to be at 0 degrees Celsius to melt ice?

In order for ice to melt, the temperature of the surroundings must be above 0 degrees Celsius. However, the water does not have to be exactly at 0 degrees Celsius. As long as the temperature is above the melting point of ice, the ice will melt.

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