When you put a bowl of water in the freezer, it takes longer to freeze compared to putting ice cubes directly into it because of the difference in the heat transfer process.
The freezing time is influenced by the concept of latent heat of fusion, which is the energy required to change a substance from a liquid to a solid state at constant temperature and pressure. When you put ice cubes directly into the water, they already have a temperature below the freezing point of water. The ice cubes release their latent heat of fusion into the surrounding water, which accelerates the freezing process.
On the other hand, when you place a bowl of water in the freezer, the water in the bowl needs to cool down to the freezing point (0°C or 32°F) before the freezing process can begin. This initial cooling process takes time as heat transfers from the water to the surrounding air in the freezer. Once the water reaches the freezing point, the actual freezing process starts, and the latent heat of fusion is released to freeze the water into ice.
So, the process of cooling the water in the bowl to the freezing point first and then freezing it into ice takes longer than directly adding already frozen ice cubes, which already have a head start in the freezing process.
Additionally, the surface area-to-volume ratio also plays a role. Ice cubes have a relatively higher surface area compared to a bowl of water, which means they can cool the surrounding water more efficiently.
In summary, placing ice cubes directly into water takes less time to freeze because they already have a lower temperature and release their latent heat of fusion immediately, while a bowl of water needs to first cool down to the freezing point before the actual freezing process begins.