Question

Which of the following would happen, when a liquid is heated in a beaker on a flame?

• A. Heated molecules become less dense, and they rise.
• B. Colder molecules from the top layers would sink to the bottom.
• C. Heat currents are set up in the liquid due to convection.
• D. Heat transfer happens in the liquid via conduction.

Answer 1

Answer: (A), (B), (C)

The correct options are
A Heated molecules become less dense, and they rise.
B Colder molecules from the top layers would sink to the bottom.
C Heat currents are set up in the liquid due to convection.

When a beaker of liquid is put on a flame, the heat from the bottom of the beaker will heat the molecules of the liquid in the bottom layers. This makes them light, and hence, they rise to the surface of the liquid. On the other hand, colder molecules in the top layers of the liquid will descent to the bottom, and get heated up. This cycle, repeats until all the liquid is evenly heated up, and there is no temperature difference.