What is the Latent Heat of Fusion and Why Does it Take Heat to Freeze Something?

[MadmanMurray]

I did a lab experiment were we measured the latent heat of fusion of ice but I am not quite sure what that is. I read that latent heat of fusion is the energy(heat) it takes to change liquid to solid. Is that true? Why would it take heat to freeze something?

 

[alxm]

I did a lab experiment were we measured the latent heat of fusion of ice but I am not quite sure what that is. I read that latent heat of fusion is the energy(heat) it takes to change liquid to solid. Is that true? Why would it take heat to freeze something?

Confusion like that is why 'latent heat of fusion' is now referred to as 'enthalpy of fusion' instead.

And in the case of water it doesn't require energy, melting is exothermic and freezing is endothermic.
By the same amount.

 

[astrokreng]

Yes, your understanding of the latent heat of fusion is correct. The latent heat of fusion is the amount of energy (in the form of heat) that is required to change a substance from its liquid state to its solid state at a constant temperature. In the case of ice, this is the energy needed to freeze liquid water and form solid ice at 0 degrees Celsius.

The reason why it takes heat to freeze something is because of the molecular structure of the substance. In the liquid state, the molecules are moving and vibrating freely, which allows them to flow and take the shape of their container. However, in the solid state, the molecules are more tightly packed and have less freedom of movement. In order to change from a liquid to a solid, the molecules need to be rearranged and this requires energy. This energy is provided by the heat, which causes the molecules to slow down and form a more organized structure, resulting in a solid state.

The measurement of the latent heat of fusion is important in understanding the properties of a substance and its behavior during phase changes. It is also important in various industrial processes, such as freezing and preserving food, and in the production of materials such as metals and plastics. I hope this helps to clarify the concept of latent heat of fusion for you.