How much is inside HOT WATER? (part 5)

. . . back to part 4 . . .

How much is inside hot water? - part 5

Owing to popular request, the hot water saga continues...

We now address two more questions:

What difference does it make if you put a lid on the pan?

How does the microwave compare as a water-boiling method?

To answer these questions, I assembled the two famous pans, the classic 1-litre measuring device, three litres of tap water, and a new character: the white microwave-safe pyrex bowl and lid.

What difference does it make if you put a lid on the pan?

To answer this question with ordinary kitchen equipment is a little tricky, since it's quite hard to judge exactly when the pan has "come to the boil". First, it starts to fizz a little; then a lot of bubbles form; then boiling starts at the walls of the pan; then boiling spreads to the middle. I tried to make a judgment of this last stage of "complete boiling".

I boiled the water in the lidless pan first; then, memorizing as best I could what I had just seen, I boiled the water in the lidded pan, peering through the glass lid to try to see what was going on.

Here are the results, expressed as durations, amounts of gas, and amounts of energy used.

pan with no lid	pan with lid on, as normal
starts forming lots of bubbles after about 3mins 40secs	starts forming lots of bubbles after about 3mins 40secs
starts boiling after about 5mins 05secs - gas used = 0.925 cubic feet	starts boiling after about 4mins 49secs - gas used = 0.90 cubic feet
0.3 kWh of chemical energy	0.29 kWh of chemical energy (2.8% less with lid than without)

Conclusion about lids

When you are bringing water to the boil, Using the lid is about 3% better than leaving the lid off.

Continue reading part 6 of How much is inside hot water...