GED Science TestPhysical ScienceMedium
A student is heating a beaker of water on a hot plate. They notice that the water at the bottom of the beaker heats up first, then rises, and cooler water from the top sinks to take its place, creating a continuous circulation. This method of heat transfer is known as which of the following?
- AEvaporation.
- BRadiation.
- CConvection.
- DConduction.
Show answer & explanationAnswer & explanation
Correct answer: C. Convection.
Convection is the transfer of heat by the movement of fluids (liquids or gases). In this case, the heated water becomes less dense and rises, while cooler, denser water sinks, creating a convection current.
Why the other options are wrong
- A. Evaporation is a phase change, not a primary method of heat transfer within a bulk fluid.
- B. Radiation is heat transfer through electromagnetic waves, without a medium.
- D. Conduction is heat transfer through direct contact, without fluid movement.
Convection
Heat transfer by the movement of a fluid (liquid or gas) between areas of different temperatures, driven by density changes.
- Occurs in liquids and gases.
- Involves the physical movement of heated particles.
- Responsible for weather patterns, ocean currents, boiling water.
Memory trick: Conduction is 'Contact', Convection is 'Circulation', Radiation is 'Rays'.