.

In respect to this, does freezing something make it heavier?

There actually are simple A set amount of a substance has a constant number of atoms and going through a phase change does not change the number of atoms, so the mass of water remains the same when it freezes. Water unlike most substances gets less dense when it freezes.

does frozen fruit weigh more than fresh? If you buy frozen berries, you weigh them frozen. In the case of the berries, it won't make a huge difference.

Similarly one may ask, is fish heavier when frozen?

The frozen fish itself may have little ice crystals which will melt and flow away. You have to make sure that all the little bits of water are weighed before and after the thawing, and that no extra bits are added, and then you should get pretty much the same weight.

What weighs more water or ice?

No, water and ice do not weigh the same. For example, if we take the same volume of water and ice in the same container, water would weigh more than ice. The reason is that water is denser than ice and the space it occupies is less as compared to that occupied by ice.