Yes, a thermos can keep things cold. Thermoses, also known as vacuum flasks, are designed to provide excellent insulation and retain the temperature of the contents inside. They are commonly used to keep liquids hot, such as coffee or tea, but they can also effectively maintain cold temperatures.
The inner chamber of a thermos is typically made of glass or stainless steel and is separated from the outer shell by a vacuum layer. This vacuum layer acts as a barrier against heat transfer, both from the outside environment to the inside and from the inside to the outside. This insulation helps to minimize the exchange of heat and keeps the contents of the thermos at their desired temperature.
To keep things cold in a thermos, you can pre-chill the thermos by adding ice water or placing it in the refrigerator prior to use. Then, pour the cold liquid or place the chilled items inside the thermos, and seal it tightly. The vacuum insulation will help maintain the cold temperature for an extended period, allowing you to enjoy cold beverages or preserve perishable items while on the go.
It's important to note that while a thermos can keep things cold, it is not a refrigeration device. Over time, the temperature inside the thermos will gradually equalize with the outside environment, and the contents may eventually lose their coldness. However, compared to regular containers, a thermos provides significantly better insulation and can keep things cold for a longer duration.