Why do sliced onions float when they are cooking???

Question

Just wondering, while making soup, all other vegetables seem to sink after cooking a while, all but the onions.. Why????

Answer 1

The density of the air inside of the onion and it is lighter than most of the vegetables.

Answer 2

Floating and sinking have to do with the density of an object, which is the amount of mass per volume.

Don't confuse mass and weight. Mass is how much stuff is there, weight is how much it weighs.

If I fill a pillow case up with feathers, and another up with lead, the one with feathers will weight less, even though the mass is the same. Why? Because the feathers are mostly air. They are less dense.

In order for something to float in a liquid, it has to be less dense than the liquid. An onion slice is less dense than water, so it floats on water. A carrot is more dense so it sinks.

Answer 3

Onions are relatively light and have a lot of surface area, so they act like a raft. If you cut the onion into chunks, the chunks would sink.

Basically they float because there's not a lot of reason for them not to. They don't exert a lot of downward pressure and spread their mass out over a larger surface area.

Answer 4

Because in the skin there are little pockets of air. As they cook the water gets into those pockets and thats why they sink as they cook

Answer 5

The density of onions is less than other vegatables

Answer 6

i am not sure but if you cook most veggies or greens they float i think it is because thay are less dence than water