Heat released during freezing of water

In summary, the water experiences no change in temperature but the thermometer does due to the heat being absorbed.
  • #1
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Homework Statement


A situation is given whereby a thermometer is placed inside acetone of 80C and is taken out. A layer of ice forms around the surface of the thermometer, does the reading of the thermometer change?


Homework Equations


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The Attempt at a Solution


At first I considered during condensation the substance (in this case, water vapour) experiences no change in temperature as heat released is the same as heat formed during the formation of bonds between water molecules. Then I considered that since heat is given out by the water molecules, the thermometer absorbs some of the heat and therefore experiences an increase in its reading. Am I correct to say that the water experiences no change in temperature but the thermometer does?BTW this is not a homework question, it is a question from my examination, and I chose to answer that the reading of the thermometer increase. I have this sinking feeling that I may be wrong :frown:
 
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  • #2
Did you mean 80C or -80C?

Imagine the thermometer was at -100C. When water vapour condenses on the thermometer it will warm the thermometer a bit. However the thermometer will also cool the water and it could cool it below 0C. It would depend on the temperature, mass and material of the thermometer as well as the mass of water.

Imagine what happens if water ice is dropped in liquid nitrogen. The water will warm the N but the N will also cool the water ice.
 
  • #3
Water vapor will continue to condense and heat the thermometer until the thermometer has reached 0C. After that, the room air will begin to heat the ice from the outside (with the thermometer remaining at 0C) until all the ice has melted. Then, the temperature of the water will begin to rise, and the thermometer temperature will follow.
 
  • #4
Well this question is purely qualitative, there are no calculations involved. Since my description of the question wasn't quite clear I shall copy the question itself

The diagram below shows a thermometer placed in a beaker of acetone and its reading is τ1. When the thermometer is taken out, and icy layer forms around the thermometer and its reading is τ2.Compare τ1 and τ2.

τ1 = τ2
τ1 Greater than τ2
τ1 less than τ2
 
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  • #5
Think in terms of a simple heat balance. An object at -80°C is put in contact with wet air at STP. Water condenses on the surface of the object - heating it up. Water freezes - heating it up. Ice cools down till its temperature is identical with the temperature of the object - object temperature goes up even further.
 
  • #6
Borek said:
Think in terms of a simple heat balance. An object at -80°C is put in contact with wet air at STP. Water condenses on the surface of the object - heating it up. Water freezes - heating it up. Ice cools down till its temperature is identical with the temperature of the object - object temperature goes up even further.

Alright looks like I was correct. Thanks Borek :)
 

1. What is heat released during freezing of water?

Heat released during freezing of water is the energy that is given off when liquid water turns into solid ice. This energy is released in the form of heat and is known as the heat of fusion.

2. Why does water release heat when it freezes?

Water releases heat when it freezes because of the unique structure of its molecules. When water molecules freeze, they form a crystal lattice structure which causes the molecules to move closer together. This movement releases energy in the form of heat.

3. What is the specific heat of water during freezing?

The specific heat of water during freezing is 334 joules per gram. This means that it takes 334 joules of energy to change the temperature of 1 gram of water by 1 degree Celsius during the freezing process.

4. How does the heat released during freezing affect the temperature of the surrounding environment?

The heat released during freezing can affect the temperature of the surrounding environment by either increasing or decreasing it, depending on the conditions. If the water is freezing at a temperature lower than the surrounding environment, the heat released will warm up the environment. However, if the water is freezing at a temperature higher than the surrounding environment, the heat released will decrease the temperature of the environment.

5. Can the heat released during freezing be harnessed for practical use?

Yes, the heat released during freezing can be harnessed for practical use. This process is known as the freeze/thaw method and is commonly used in refrigeration systems. By utilizing the heat released during freezing, refrigeration systems can effectively cool and preserve food and other perishable items.

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