1 kilogram of feathers has more volume than 1 kilogram of brick. feathers have less density than brick therefore they take up more space in a container.
density & buoyancy
when you place an object in a liquid such as water and it floats, it is said to have buoyancy.
the more density an object has, the less buoyancy it has, and it will sink.
swim bladder
a fish controls its depth by adding or subtracting gas from its swim bladder. by squeezing the bladder and releasing gas the fish becomes more dense and therefore it sinks deaper. if the fish adds gas to the bladder it becomes less dence, increasing its buoyancy and it will rise up in the water.
