If you were to place a mobile phone inside a vacuum flask (also known as a thermos) and then put the vacuum flask in the freezer, the phone would eventually reach a temperature close to the freezer's internal temperature. However, the process of cooling down the phone inside the vacuum flask would be much slower compared to placing the phone directly in the freezer.
A vacuum flask is designed to provide excellent thermal insulation, which means it minimizes heat transfer between the contents inside and the external environment. It achieves this by having a double-wall construction with a vacuum layer in between, which prevents heat transfer by conduction and convection. Additionally, the inner walls are usually coated with a reflective material to minimize radiation heat transfer.
While the vacuum flask would slow down the cooling process, it would not completely prevent the phone from freezing if left inside the freezer for an extended period. The freezer's temperature is typically well below freezing point, and eventually, the phone's temperature would approach that of the freezer.
It's essential to note that exposing electronic devices like mobile phones to extremely low temperatures, especially below freezing, can be harmful to their components. Batteries, in particular, can be affected, leading to reduced performance or even permanent damage. Therefore, it's best to avoid subjecting your mobile phone to freezing temperatures intentionally. If you need to store your phone in a cold environment, keep it in a temperature range recommended by the manufacturer to ensure its optimal functioning and longevity.