Which statement about convection is true?

Which statement about convection is true?

• A. It can occur in solids
• B. It can occur in both liquids and gases
• C. It occurs only in liquids
• D. It occurs only in gases

Answer: (B)

Convection is heat transfer created by the bulk movement of a fluid. For convection to occur, the medium must be able to flow, and heating must create a density difference that drives circulation: warmer, less dense regions rise while cooler, denser regions sink. This is why you see convection in liquids and gases—water boiling on a stove, air circulating in a room, or warm air rising near a heater. In solids, the atoms can’t flow past each other, so there’s no bulk motion to carry heat through convection. Heat in solids mostly moves by conduction (through contact and lattice vibrations) or, in some cases, by radiation. So the statement that convection can happen in both liquids and gases is the true one, while it does not occur in solids under ordinary conditions.

Convection is heat transfer created by the bulk movement of a fluid. For convection to occur, the medium must be able to flow, and heating must create a density difference that drives circulation: warmer, less dense regions rise while cooler, denser regions sink. This is why you see convection in liquids and gases—water boiling on a stove, air circulating in a room, or warm air rising near a heater.

In solids, the atoms can’t flow past each other, so there’s no bulk motion to carry heat through convection. Heat in solids mostly moves by conduction (through contact and lattice vibrations) or, in some cases, by radiation. So the statement that convection can happen in both liquids and gases is the true one, while it does not occur in solids under ordinary conditions.