Final answer:
A watch glass is used to cover a beaker of boiling water to prevent splattering, it reduces the heat transfer necessary to keep the water boiling. Running hot water over a tight metal lid can aid in opening it by causing expansion. A thermos bottle's design, including a vacuum and silvered walls, minimizes heat transfer. The correct answer is D.
Step-by-step explanation:
The item used to cover a beaker of boiling water to prevent splattering is d) Watch glass. A watch glass is a concave piece of glass commonly used in chemistry labs to cover beakers, allowing for evaporation while preventing contamination or splattering. Covering a beaker with a watch glass reduces heat transfer, thereby reducing the energy required to maintain the boiling by containing the steam and heat.
As for the question about hot water and a tight metal lid, running hot water over a tight metal lid on a glass jar can help in opening it because it causes the metal to expand, which can loosen the seal and make it easier to unscrew the lid.
Concerning the thermos bottle (Dewar flask), its design includes various parts to minimize heat transfer: the vacuum prevents conduction and convection; the silvering of the walls reflects radiant heat; the thin-walled long glass neck reduces the area through which heat can be transferred; the rubber support minimizes heat transfer from the bottle to the external surface; the air layer provides slight insulation; and the stopper aids in preventing heat loss through the top of the flask.