Question

Seema takes her coffee in a metallic mug, whereas Tina takes her coffee in a glass
mug. Coffee in both the mugs is poured at the same time, in the same amount, and at
the same temperature. Coffee in which of the mugs will cool faster and why?

Answer 1

Explanation:

mug is a type of cup typically used for drinking hot drinks, such as coffee, hot chocolate, or tea. Mugs usually have handles[1] and hold a larger amount of fluid than other types of cup. Typically, a mug holds approximately 8–12 US fluid ounces (240–350 ml) of liquid.[2] A mug is a less formal style of drink container and is not usually used in formal place settings, where a teacup or coffee cup is preferred. Shaving mugs are used to assist in wet shaving.

Answer 2

Answer:

Thermal conductivity largely depends on material properties. Pure metals are extremely good conductors of heat because of the presence of free electrons. Alloying metals with impurities will reduce thermal conductivity because the impurities will act as scattering centers lowering the motion of electrons. Therefore, hot coffee contained in plain carbon steel cup will cool faster than the coffee contained in a stainless steel cup. Next, in glass and ceramics (both crystalline and amorphous ceramics), the atomic structure is highly disordered and irregular. Conduction takes places because of lattice vibrations - greater the lattice irregularity, more the vibration and hence more efficient the heat transfer. However, efficiency of heat transfer due to free electrons (as in pure metals) is far greater that that due to lattice vibrations (as in amorphous and crystalline substances). Thus, thermal conductivity of steel (~16 W/m.K) is way higher than either glass (~0.8 W/m.K) or ceramics (~1.5 W/m.K). Further, the ceramic mugs are made to have pores which further lowers thermal conductivity. Thus, heat loss takes place in the following order by conduction mode: Metal (steel) > Glass > Ceramics