3. Two identical cups of cocoa are kept on a table.
One has a metal spoon in it and the other does
not. After 5 minutes, which cocoa cup
will be
cooler?
4. Several days after the end of a snowstorm, the
roof of a house gets completely covered with
snow. Another house has no snow on its roof.
Which house is better insulated?
5. Why are the tumblers, used to sip hot drinks
not made of metals?
a
Answers
The one with the spoon will be cooler. Metal can gain and lose heat quickly, so the spoon can take heat from the cocoa quickly and lose it to the atmosphere quickly.
Metals are very conductive to heat. So putting a hot drink in a metal container will allow it to cool more quickly than if you put it in an insulating container (like glass). It also means the outside of the container gets hotter, so it would be uncomfortable to hold a hot drink in a metal tumbler. And it’s the same for cold drinks; metal tumblers would be uncomfortable to hold and would warm the drink faster.
Glass is transparent and allows you to see what’s inside. For many drinks, visual appeal is part of the enjoyment, so glassware enhances the drink. A famous historical example is that beer was traditionally a cloudy beverage (due to yeast and other unfiltered sediment). It didn’t matter because beer was a cheap drink served in wooden, metal, or ceramic tankards. You couldn’t see how cloudy it was. About the time glassware became cheaper to manufacture, British brewers invented “pale ale”, a more light-colored, clear, golden beer that could be appreciated in the new bar glasses.
Affordable metals corrode, so finding a metal suitable for a drinking vessel is difficult. Iron would rust; copper would tarnish. Lead is poisonous, tin and zinc are brittle, and all of them impart a taste. The best options are probably tin-lined copper (currently in vogue for “Moscow Mule” drinks) or else low-lead pewter alloys. Glass is easier to care for than any of them.