Question

A capped empty glass bottle floats into tank, whereas uncapped empty glass bottle sink . Why?

Answer 1

A capped empty bottle is lighter as it contains air which also makes it less dense. This is why it floats on water due to being less dense than water.

A open bottle when placed in water would allow some water to enter inside. This would add to its weight and make it more dense than water. This is why it would eventually sink due to being more dense than water