Question

Saving Energy: Suppose you are cooking spaghetti for dinner, and the instructions say “boil pasta in water for 10 minutes.” To cook spaghetti in an open pot using the least amount of energy, should you turn up the burner to its fullest so the water vigorously boils, or should you turn down the burner so the water barely boils?

Answer 1

Solution

In order to boil spaghetti for 10 mins it is better idea bearing in mind energy saving, to turn down the burner so that water barely boils. This is due to the fact that at the boiling point, the energy you supplying to the water will be used to convert it into water vapours and temperature of water remains at constant value 100°C at normal atmospheric pressures. This is called latent heat of vapourization. Water vapour at 100°C contains more internal energy than water at 100°C . This latent heat is used to overcome intermolecular attractive force between water molecules and get separated.

Thus the summary is that heat you supplied to boiling water is wasted it will not help to sphegatti faster because temperature remains the same irrespective of the heat energy you supplied. This if you turn up the burner, more heat energy thus more fuel will be wasted. Thus it is better to turn down the burner and wait for sphegatti to get cooked.