Question

Which items are true concerning a typical "thermos bottle"?

radiation is hindered by the silver coatings
convection is not possible because of the vacuum
the glass walls will not conduct heat
the silver coatings stop convection losses
conduction losses are prevented by the vacuum

Answer 1

True:
- radiation is hindered by the silver coatings — the reflective (silvered) inner surfaces reduce radiative heat transfer across the vacuum gap.
- convection is not possible because of the vacuum — with no gas in the gap there is nothing to convect, so convective heat transfer between the inner and outer walls is prevented.
- conduction losses are prevented by the vacuum — the vacuum eliminates conduction through a gas in the gap.

False:
- the glass walls will not conduct heat — the glass does conduct heat (albeit relatively slowly); conduction through glass and the neck/supports is a real heat loss path.
- the silver coatings stop convection losses — the coatings reduce radiation, not convection; convection is already prevented by the vacuum.

(If precision is required: the vacuum prevents conduction through the gap but not conduction through solid supports or the stopper, which remain heat-loss paths.)