# Heat Removal from Ice: How Much Energy?

• Savage1701
In summary, the conversation discusses the process of converting one gallon of water at 32.1 degrees F to ice and then back to water, with the assumption that 1200 BTU's of heat energy is required to convert the water to ice. It is stated that in order to lower the temperature of one gallon of water 1 degree F, approximately 8.34 BTU's of heat energy must be removed. It is also mentioned that the specific heat capacity of ice is less than half that of water, at 2050J/Kg compared to 4180J/kg for water. Finally, it is concluded that in order to melt the ice back into 32.1 degree F water, 266 BTU's
Savage1701

1. I have one gallon of water at 32.1 degrees F
2. It is correct that in order to lower the temperature of one gallon of water 1 degree F, approximately 8.34 BTU's of heat energy must be removed from that water.
3. Latent heat of fusion requires that approximately 1200 BTU's be removed from the water to convert it into ice.

Let's assume that I remove that 1200 BTU's of heat from the water and it then transitions into ice. Now let's further assume I place that gallon of ice, which is at 32 degrees F, into a room that is maintained at 0 degrees F by refrigeration.

Am I correct in assuming the following:

1. The ice will release an additional 266 BTU's of energy to reach equilibrium temperature with the room, i.e., 0 degrees F? Of course, this assumes the refrigeration equipment is capable of removing that heat from the room and maintaining 0 degrees F.

2. In order to melt that ice back into 32.1 degree F water, I will need to add 266 BTU's to that gallon of ice to bring it to its transition temperature of 32 degrees. I will then need to add 1200 BTU's of heat energy to cause that ice to melt back into water that is just above the freezing point?

Thanks for any help.

Not quite, the specific heat capacity of ice (and steam oddly enough) is less than half that of water. So it only takes 2050J/Kg to raise ice 1degC rather than 4180J/kg for water (same ratio in imperial units).

Otherwise you're correct.

Thanks for the prompt and helpful reply. Good to know I had not forgotten everything from my HS and college physics 20-some years ago.

Thanks again.

## 1. How much energy is required to remove heat from ice?

The amount of energy required to remove heat from ice varies depending on the initial temperature of the ice, the desired final temperature, and the mass of the ice. However, on average, it takes about 334 joules of energy to remove the heat needed to melt 1 gram of ice at 0 degrees Celsius.

## 2. Can heat be removed from ice without melting it?

Yes, heat can be removed from ice without melting it. This process is called sublimation, where the ice transitions directly from a solid state to a gas state. However, this requires a very low pressure environment and is not a practical method for heat removal in most situations.

## 3. How does the rate of heat removal affect the melting of ice?

The rate of heat removal does not affect the melting of ice. The melting point of ice is a constant temperature of 0 degrees Celsius, regardless of how quickly or slowly heat is removed from it.

## 4. What are some common methods for removing heat from ice?

Some common methods for removing heat from ice include using a refrigerant system, using chemical reaction-based cooling systems, or using liquid nitrogen or dry ice. These methods typically rely on the transfer of heat energy from the ice to a colder medium, such as a gas or liquid.

## 5. How does the composition of ice affect the amount of energy required for heat removal?

The composition of ice does not significantly affect the amount of energy required for heat removal. However, ice that contains impurities or air bubbles may have a slightly lower melting point, which could affect the amount of energy needed to remove heat from it.

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