Convection in Heated Water

Steps:

• Heating water increases its temperature, causing thermal expansion.
• Thermal expansion reduces the water's density compared to cooler water above.
• Less dense hot water becomes buoyant and rises due to gravity.
• This upward movement initiates convection currents in the beaker.

Why A is correct:

• Density decreases upon heating (from thermal expansion), and buoyant force drives upward movement, per Archimedes' principle.

Why the others are wrong:

• B: Incorrectly states no movement; convection causes rise.
• C: Wrong on density (decreases, not increases) and ignores movement.
• D: Density decreases, not increases; upward movement is correct but paired wrongly.

Final answer: A