When an air bubble at the bottom of a lake rises to the top, it will

An air bubble rising from the bottom to the surface experiences a decreasing hydrostatic (ambient) pressure; gases expand when the external pressure on them falls. Texts note that pressure compresses gases (higher pressure → smaller volume), so a reduction in pressure causes the gas to occupy more volume [1]. More specifically, as a parcel (or bubble) rises the ambient pressure decreases with height and its volume increases accordingly [2]. This behavior is described by Boyle’s law (PV ≈ constant for a given amount of gas at near-constant temperature), which directly explains why the bubble grows as the surrounding water pressure drops during ascent .

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 9: The Amazing World of Solutes, Solvents, and Solutions > 9.5.3 Effect of pressure on density > p. 148
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > A Parcel of Rising Air > p. 297