The solid form of a substance is usually more dense than its liquid and gaseous forms. similarly the liquid form is usually more dense than the gaseous form.
which of these breaks this general density rule?
a. ice floating in a glass of water
b. vapor rising from a hot cup of tea
c. cooled magma sinking in a lava flow
d. a hot air balloon falling as the gas inside cools

The solid form of a substance is usually more dense than its liquid and gaseous forms. Similarly the liquid form is usually more dense than the gaseous form. Ice floating in water is an exception that breaks the general density rule. So option “A” is the correct option in regards to the given question. In case of ice formation, actually the density of water decreases by about 9%. This is the main reason behind ice floating in water. Pure water has the maximum density at 4 degree centigrade.

Noble gases is far right

Oxygen= 88ghydrogen= 12g