Is the molecule gaining or losing energy when an ice cube melts into water?

Answer 1

Think of it this way: When water is frozen the molecules are barely moving, that's why it's a solid. When it starts to melt, the particles pick up speed( they're moving faster), so the ice is absorbing energy ( in the form of heat ). This is known as an endothermic reaction.

Answer 2

It's gaining energy.

Water is often misunderstood. At ~0 c, water can be solid (ice) and it won't ever melt unless energy is put into it. Similarly, at ~0 c water can also be liquid and won't ever solidify/freeze unless energy is expelled from it.

This means if I cool a cup of water to ~0c and NO LESS, it won't freeze. Or heat ice to ~0c and no more, it won't melt. Because both states are actually very stable and at ~0c, there's no spontaneous need to change.

Now, we can take this a bit further. If I have ice at ~0c and put energy (heat) into it, it won't raise in temperature. This energy goes into turning the ice into water while the temperature remains at ~0c. Only when it has converted into water, does the temperature begin to rise again. The same is true of the reverse.

So when ice melts, it is actively gaining energy. When it freezes, it is actively losing energy.

Answer 3

When an ice cube melts into water, the molecules are gaining energy. This is because the heat energy from the surroundings is used to break the bonds holding the ice molecules together, allowing them to move more freely as liquid water.

Answer 4

Melting is endothermic, it gain energy into itself.