Answer to Question #122145 in Molecular Physics | Thermodynamics for Quanda

Question

1) Smoke from a burning rubbish heap is observed to move upwards in a wavy manner. Explain:
(i) why the smoke moves upwards
(ii) why the movement is wavy
(iii) how the movement of the smoke is different from Brownian motion

2) Hot tea from the same flask is served into two cups of the same shape and same volume, one made of glass and the other of silver. State, giving reasons in each case
(a) which cup of tea colds fast
(b) the method of heat transfer by which the two cups lose heat at the same rate

Answer 1

Answer: 1)The smoke is heated to a certain temperature. And since the heating of gases increases the distance between gas molecules, the density of the gas decreases accordingly and becomes less than the density of air. And under the condition of aeration, gases with a lower density than the density of air rise up. Smoke and a balloon rise because they are displaced by heavier air, which falls under the action of gravity.

If there are wind currents, the smoke rises in waves.

2)Tea in a silver cup cools faster because silver has a higher thermal conductivity.

Substances with low thermal conductivity are used where they should be stored

body from cooling or heating.

The method of heat transfer by which two cups lose heat at the same rate is called radiation.