When water at  0∘C  freezes to form ice at the same temperature of  0∘C , then it:

When water at  0∘C freezes to form ice at the same temperature of  0∘C, then it undergoes a phase change from a liquid to a solid. This process is known as freezing or solidification. Here are the steps involved:

1. Cooling: The water is initially at a temperature of  0∘C. It needs to be cooled further in order for the phase change to occur.

2. Formation of ice crystals: As the water is cooled, the molecules slow down and come closer together. At  0∘C, the water molecules arrange themselves into a regular pattern, forming ice crystals.

3. Release of heat: During the freezing process, heat is released. This is because the water molecules lose energy as they transition from a more disordered state (liquid) to a more ordered state (solid). The release of heat is why freezing water can sometimes feel warm to the touch.

4. Equilibrium: Once the water has completely frozen into ice, it reaches a state of equilibrium where the rate of freezing is equal to the rate of melting. At this point, the temperature remains constant at  0∘C until all the ice has melted or further cooling occurs.

Overall, when water at  0∘C freezes to form ice at the same temperature, it goes through a process of cooling, formation of ice crystals, release of heat, and reaches a state of equilibrium.