The air sealed between two panes of glass in some windows to reduce the flow of heat passing through the window increase the flow of heat passing through the window reduce the visible light passing through the window increase the visible light passing through the window

The air sealed between two panes of glass in some windows helps to reduce the flow of heat passing through the window.  Even though the windows are more expensive to build, that little bit of trapped air in there is a very effective INSULATION.  It makes the house easier to keep warm in Winter, and easier to keep cool on Summer, and both of those save on the cost of gas or electricity for the house.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it