If you study physics, you should be able to explain why the sky is blue. If biology is your thing, you ought to be able to answer where babies come from. Chemistry doesn't have any great standard question, but there are some everyday phenomena you should be able to explain.
Marcelo Brito Filho
Even better, know how to prevent the tears.
Architetto Francesco Rollandin, openclipart.org
If ice didn't float, lakes and rivers would freeze from the bottom up, basically causing them to solidify. Do you know why solid ice is less dense than the liquid?
You do realize not all radiation glows green and will mutate you, right?
You can wet your hair all you want, but that won't get it clean. Do you know why soap works? Do you know how detergents work
Silsor, Wikipedia Commons
Do you know better than to mix bleach and ammonia or bleach and vinegar? What other everyday chemicals pose a hazard when combined?
Tony Roberts, morguefile.com
Chlorophyll is the pigment in plants that makes them appear green, but it isn't the only pigment that is present. Do you know what affects the apparent color of leaves?
Aramgutan, Wikipedia Commons
First, you should know the answer is 'yes' and then be able to explain why it's completely impractical.
Darren Hauck/Getty Images
Does it do any good? How does it work? Are all salts equally effective?
Mark Gallagher, Wikipedia Commons
Do you know how bleach works?
U.S. Geological Survey
No, you don't need to be able to list every single one. You ought to be able to name the top three without thinking. It's good to know the top six.