Andreas Hauslbetz/Alamy
Eric Kvaalen
Les Essarts-le-Roi, France
The optimal ratio is zero water. The time is proportional to the amount of heat that needs to be added to bring both the peas and the water to the boiling point. That amount of heat doesn’t depend on whether the peas and water exchange heat. But the more water you add, the more heat is needed to bring it to a boil.
With frozen green beans, what I do is put them in a bowl with tap water while the water in the pot is heating up. I usually change the water in the bowl once or twice. The beans are thawed by the time the water is boiling, and I then put them in the pot.
Trevor Campbell
Berrima, New South Wales, Australia
That is 100 per cent peas, 0 per cent water. Of course, this wouldn’t work well on the stovetop, but it does work in a microwave oven.
I see where the questioner is coming from, as adding water to the peas raises the overall starting temperature, but that isn’t relevant. You need to add enough heat to the overall mix to raise the temperature of the peas from frozen, and raise the temperature of whatever amount of cold water you add. Any mixing of the two components beforehand just moves the heat energy around, and doesn’t have a material effect on how much energy you need to add to the system. There is a little caveat, in that heat moves more quickly when the difference between two objects is greater (Newton’s law of cooling or Fourier’s law), but this only amplifies the benefit of 100 per cent peas.
“
Sharing our thoughts and our observations with each other has been absolutely fundamental to human evolution
“
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
91av retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
