35. Birds such as ducks, geese, and swans have greater densities than water, yet they are able to sit on its surface. Explain this ability, noting that water does not wet their feathers and that they cannot sit on soapy water.

Explanation:

The force which is responsible for an object to float over a liquid is the buoyancy force and it depends on the density of the liquid and the object which means that the object’s density should be less compared to the liquid density to float over the water

In case of birds such as ducks, geese, and swans, they have greater densities than water, yet they are able to sit on its surface because they have special glands which secretes oil

The secretion of oil makes their feathers oily and hence they can shed the water on feathers and feathers in turn do not get wet

These birds can then float easily on water by their webbed feet and larger surface tension of water

Surface tension is the elastic tendency of the surface of the fluid that makes it acquire the least surface area possible