why do your hands curl when they are cold or relaxed

also i have all my questions here in this blog http://questions-about-the-world.blogspot.com/

I was walking along a canal several days ago, and, the UK weather being what it is at the moment, the canal was frozen. However under all the bridges that crossed the canal, whether footbridge or road bridge, the water was unfrozen. What is it about the bridges that stops the water under them from freezing?

My girlfriend and I were having an argument the other day. Sometimes when it is cold in the kitchen, I turn in the gas hob to warm the place up. The argument is that she claims that the room gets hotter if you put a pot of water on the hob to boil and let the room get steamy. I disagree and think that the room gets just as hot without boiling a pot of water.

Who is right? Does the room get hotter with the pot of water or does the room get just as hot without it?

After visiting Iceland last year you could see frozen waterfalls coming down from the cliffs? How do these freeze since surely they have too much kinetic energy?

My friend and I work in a molecular biology lab, with regular access to a -80C lab freezer.  The other researchers' and students' sample tubes/vials are kept in boxes or sealed ziplock bags in the freezer.  Occasionally, after a period of storage, a random ziplock bag will be inflated almost to bursting point.  On speculating why this could be, I suggested that the water droplets in the air that is trapped in the bag will freeze rapidly and hence expand, and the pressure increase causes the bag to inflate.  My friend disagrees, reasoning that expansion of water droplets alone can't possibly account for the huge increase in volume inside the bag.  Who is right or, if neither, what is the correct explanation?

Surely if they are good conductors then they will absorb the heat easily, just as they do when you place your hand onto the surface?

At the risk of flogging a dead, er, penguin. Why don't polar bears' feet freeze?

Paul Newcombe, Zurich, Switzerland

(Image: US federal government / Wikimedia Commons)

James Scowen, London, UK