Outline why a given mass of water has more internal energy than the same mass of ice at the same pressure?

To achieve maximum score, you are expected to define every term that you will use. Therefore in this case define internal energy (the sum of the potential and the (random) kinetic energy of the molecules of a substance).
Answer after definition: Since the temperature is the measure of internal energy, and the water is inarguably is on higher temperature therefore has more internal energy.