Jean Cunningham, by email, no address supplied

Recently, a friend of mine did his 8th grade science fair project. He decided to test whether pure water, water with flour in it, or water with salt in it would evaporate (and thus be purified) the fastest. He found that the flour went the fastest, the salt was next, and the pure water was actually the slowest. He did say that he used the same volume of total liquid overall, not just the same volume of water, so that could have been a factor by decreasing how much needed to be evaporated. But the margin was too large for this to be the only factor. Does anyone know why this would happen?

I have been informed by my family that the love of soup is genetic for the Scots. Myself, I can take of leave it, I am confused to whether it is a main or an app.

This weekend however I popped a bowl of soup into the microwave, and after 2 minutes when I reached in to get the bowl back out I found that the bowl was so hot that I an oven glove was required to retrieve it. The contents however were only lukewarm. I am ashamed to admit that I know very little about microwave ovens, it is therefore perhaps unsurprising that I am perplexed as to why the device would heat the ceramic bowl more than it would the contents. Emperical study would suggest that some ceramics get hotter than others. What's going on here then?

If you played the same note, in 500 versions of exactly the same speakers (so all the same frequencies) at the same distance from the receptor (ear or decibel meter), would it be the same volume? 

If it would increase, how much by and why? 

Would it be 500 times? Or would some be cancelled out?

Thanks!

I have a tub of sodium hydroxide granules for use as a drain cleaner. When I poured some into a small amount of water in my sink, small splinters of a silver metal magically appeared. At first I thought it must be a reaction with the chrome plated plug hole. However, I get the same reation if i just pour some in a glass of tap water. The splinters are hard and metalic and appear to be aluminium. What on earth is going on here?

What gives chestnut mushrooms their brown colour? The colour can be wiped away, leaving what looks like a standard white mushroom.

Barry Strong, Manchester, UK

Virtually every anti-bacterial cleaning product that I buy claims to that it will kill 99.9% of bugs. So my questions is - what type of bacteria or viruses are the 0.1% that these products can't kill? They really must be the sort of thing that you wouldn't want to meet down a dark alley.

These are the photographs of a strange bug I came across during my stay in Manipur state of North East India. The dorsal view of the insect resembles a human face.  This semblance to human face doesn't appear to be by chance. What evolutionary advantage could have favored such an adaptation.

These are the photographs of a strange bug I came across during my stay in Manipur state of North East India. The dorsal view of the insect resembles a human face.  This semblance to human face doesn't appear to be by chance. What evolutionary advantage could have favored such an adaptation.

Why does an opened bottle of champagne not go flat (nearly as quickly as it would) with a stainless steel teaspoon in the top?