The skin of the orange has pockets of air. This makes the overall density of the orange lower than water, hence the whole orange can float. Without the skin, the ‘naked’ orange is denser than water hence it sinks.
But maybe we should include the feeling of the ‘naked’ orange 🙂 😀 hahaha
Convection is a process in which thermal energy is transferred within a fluid (liquid or gas) due to the difference in density which creates a current.
The video below shows the convection current in a heated tube filled with water. Colour dye is added to enable us to see the convection current through our naked eyes.
Other examples in our daily lives:
In some supermarket, the seafood are placed outside of air-conditioned place. The seafood is kept cold by putting crushed ice covering the seafood to keep the them cold and fresh.
Refer to this Sci Physics question N2008P2Q6(b)
Solutions:
For the solid that does not melt, when thermal energy is absorbed from the surrounding food, its temperature starts to rise. So it is not so effective at keeping the food cool.
For ice-pack, when thermal energy is absorbed from the surrounding food, it starts to melt. During melting process, a much larger quantity of thermal energy is absorbed from the food to melt per unit mass of ice, the temperature remains constant at 1oC, and the melting process is long. Hence ice-pack is more effective at keeping the food cool.
Related posts about ice:
Density of ice – Why ice floats on water?
Will whole lake be frozen during winter?
In an experiment to determine the density of the sand, the measurements as shown below are obtained.
If the density of water is 1.00 g/cm3, what is the density of sand?
Evan's Space 