Multiple choice, explain You put some potatoes in a big pot of cold water with t

Question

Multiple choice, explain

You put some potatoes in a big pot of cold water with the lid not too tightly closed. Which of the following methods to cook the potatoes would use the least amount of energy? Explain your reasoning.

a) Put the heat on full force. But when the water boils, turn the heat way down so that the water just keeps boiling.

b) Turn the heat on full force, and keep it there.

c) Turn the heat on very low. But when the water boils, turn the heat way up so that

the water keeps boiling.

d) Turn the heat on very low, and keep it there.

e) Put the heat at some medium value.

Explanation / Answer

The answer to this question is

a) Put the heat on full force. But when the water boils, turn the heat way down so that the water just keeps boiling.

Explanation:

If the heat is put low, it will take a long time for the water to boil. Also a lot of energy is wasted because some of it escapes from the pot, heat the surrounding air, lost from the rising water vapor.

So heating the water faster will minimize the energy by reducing the escaping heat and waste heat .

Now after reaching the boiling point . turn the heat way down so that the water just keeps boiling. At boiling temp , the pressure of water is equal to atmospheric pressure . Because the lid is not tightly closed, once you reach the 100C mark for water it remains same regardless of the amount of heat is supplied . So keep low on heat and maintain the boiling temp of water to cook the potatoes.

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