Conventional freezers are designed to maintain temperatures below the freezing point of water, which is 0 degrees Celsius (32 degrees Fahrenheit). The freezer's internal temperature is typically set to be slightly below this freezing point, usually around -18°C (0°F) or lower.
When you place water in a freezer, it will eventually freeze because the temperature inside the freezer is lower than the freezing point of water. The freezer continuously removes heat from the water until its temperature drops below 0°C (32°F), causing the water molecules to slow down and arrange themselves into a solid crystal lattice, forming ice.
The reason why conventional freezers typically don't go lower than 0°F (-18°C) is for energy efficiency and practical reasons. Lowering the temperature further would require more energy and might not provide significant benefits for most household food storage needs. Additionally, some freezers are designed for a specific temperature range, and going too low may lead to issues with the freezer's components or the quality of frozen food.
It's worth noting that there are industrial and scientific freezers available that can reach much lower temperatures, even down to cryogenic levels, but these are specialized devices used for specific applications, such as in laboratories or for long-term storage of certain sensitive materials.