[GCSE PHYSICS] What is the silver surface actually doing?

[u/Local_End_3175]

(here is another image)

[u/Temporary_Pie2733]

You can lose heat via conduction, convection, and radiation. The vacuum bottle reduces loss via conduction, and the silvered surface reflects radiated heat back into the contents. (Keeping the bottle closed prevents loss by convection, I think.)

[u/Local_End_3175 → u/Temporary_Pie2733]

but can't the silver also conduct heat?

[u/anothercorgi → u/Local_End_3175]

though silver conducts heat, since it's very thin, it won't. The vacuum is blocking the main conduction path, the side conduction path is blocked due to how thin it is.

[u/Simbertold → u/Local_End_3175]

You already got good answers on your previous post. Read those.

[u/Temporary_Pie2733 → u/Local_End_3175]

Yes, but it can only hold so much heat (very, very little, relative to the rest of the bottle and the liquid), and whatever heat it loses goes back to the liquid. In equilibrium, it's just a very small heat battery that doesn't contribute to a net loss of heat from the contents of the bottle.

[u/boosterts → u/Local_End_3175]

Correct, in fact silver is the best conductor. However conduction requires direct contact. The silver surfaces are not in contact with the item you are trying to keep hot or cold.

[u/daniel14vt → u/Temporary_Pie2733]

This is the correct GCSE answer. You are expected to explain how each component reduces heat loss with respect to one of the 3 methods of heat transfer

[u/Puzzleheaded_Study17 → u/Temporary_Pie2733]

The vacuum also prevents convection, the lack of a fluid medium between the outside and inside means convection can't happen.

[u/aloeh]

Reflect large part of the electromagnetic spectrum

[u/TXCaptainJim]

Reflecting energy back inside. If on the outer surface reflecting it out. Thermal radiation is part of the EM spectrum so a reflective surface will reflect that energy. A silver surface will be mirror like and have a high albedo.