Question

the walls of a plastic bottle tend to get deformed or crushed inwards when the bottle is closed after pouring some hot water in it why

Answer 1

A plastic bottle collapses when we pour hot water into it. It is because the air is pushed out from the bottle and steam is created inside it. After closing the bottle, this steam condenses and because some air is pushed out, vaccum is created in the bottle which leads to its deformation.