Why does an air bubble rise through still water?
Show answer & explanation
Answer: The air inside is lighter than the water, so it rises
The water surface pulls them up like a suction cup — The surface does not suck a submerged bubble upward. The upward force comes from pressure differences around the bubble, even when it is far below the surface.
The air inside is lighter than the water, so it rises ✓ — An air bubble weighs much less than the water it displaces, so buoyancy exceeds its weight. Water pressure is greater at the bubble’s bottom than at its top, giving a net upward push. This works in cold water too; heating is not required.
The water heats the air, so it expands and rises — A bubble need not be heated to rise through water. Water pressure increases with depth, so the pressure difference pushes the bubble upward even at a uniform temperature.
More Physics in Daily Life questions
- In a warm office that already reads 26 C, which change can make people feel cooler without lowering the thermostat?
- Why might 26 C feel acceptable in a breezy naturally ventilated summer building but too warm in a sealed winter office?
- On a warm, humid day, why can a 27 °C room feel worse once your skin is sweaty?
- Why can moving air make a 27 C room feel cooler without changing the thermometer?
- Why can a desk beside a cold window feel chilly even when the thermostat across the room still reads 22 C?
- Why might someone who just climbed stairs feel warm in a 22 C room while someone sitting in a T-shirt feels chilly?