When 0 ℃ ice melts into water, its volume shrinks due to the constant temperature. Why does the intermolecular distance decrease and the internal energy increase?

When 0 ℃ ice melts into water, its volume shrinks due to the constant temperature. Why does the intermolecular distance decrease and the internal energy increase?

When ice melts into water, it must absorb heat,
The temperature of the system remains unchanged,
So the heat absorbed is converted into molecular potential energy
That is, the internal energy increases
I hope it will help you