Heating the air inside causes the bottle to expand-the presure inside is enought o force the walls out,
plastic
The volume inside the bottle gets smaller.
It floats because the water is heaver then the bottle. The bottle is light so it floats. No,It floats because the particles are free to move inside but with water in it there is not enough space for the particles to move so it floats.
it might melt
Because the substance inside the bottle is highly volatile and can be lost by evaporation if the bottle is not closed.
The air inside shrinks its space needed.
it moist inside the plastic
With a butter knife. Just dig it.
When the bottle is put in the hot water the air inside it heats up and expands (the atoms become more energised and move farther away from each other). When the lid is put on and it is put in the fridge, the air contracts; the pressure inside the bottle becomes lower than the air pressure outside the bottle and it gets crushed.
double the amount of water that fits inside the bottle.
to close the water inlet after the cistern is full