I saw a rather neat photo the other day and I thought I'd share it. And set the explanation as a little quiz!
The photo shows a beaker of water with two ice cubes in it. One is floating at the surface, just as expected. The other, however, has sunk to the bottom. It isn't an optical illusion. There isn't a lead sinker in the second cube. Nor is there any other trickery. The explanation relies on science. What is going on?
BTW There are a few of you out there who will solve this in a millisecond, .... or bloody well should!! How about letting those who have to get the thinking caps on have their bit of fun?
Is the correct answer. Congratulations, I owe you a Mars bar.
Yes, the normal ice cube is H2O and the other is D2O. Normal water has an atomic weight of 18 (16+1+1) but D20 has an atomic weight of 20 (16+2+2). Since both have the same number of molecules per mL the 'isotopically heavy' ice is also actually physically heavier. [I am assuming that the oxygen-16 : oxygen-18 ratio is normal but if it is also enriched then the ice would be even heavier.]
The photo was submitted on a mailing list in response to an request for a photo which demonstrates stable isotopes. There is another member of IIS who also measures stable-isotope ratios for a living so for him this would have been trivial and I think some others may also have a professional reason to understand this; they were the people who I wanted to stay mum.
I wondered about that but don't know enough about heavy water without looking it up.
I was not sure on the dry ice (I know it does not float in water, been there done that for my 6YO when using it to strip sound deadening form a car) as I could not pick up from the image if there were CO2 bubbles coming from it.
Heavy water is poisonous when taken in large quantities, but not in a cupful.
Think how our world would be constructed if ordinary ice sank. This is another facet of the Goldilocks Enigma - "Why is the Universe so right (locally) for us to be here?"
I'm a devotee of that school which says we shouldn't be all surprised that it is, because if it was not, we would not be here to wonder at it. The Cosmos was first, we were second by a long way.
Heavy water is poisonous when taken in large quantities, but not in a cupful.
And ultra-pure water is also bad for you if you drink too much. I think it washes electrolytes from your system. I'm not sure why heavy water would be poisonous. Presumably the slightly greater bond-energy of heavy water impedes or facilitates a biochemical pathway.
Marty and Col are on the right track - but no cigar.
Col, ice made from ordinary tap water floats in water (and whisky ).
What do you mean "no cigar"? Heavy ice is frozen heavy water. I know that it sinks in tap water. I stated "heavy ice" so as not to actually give it away.
Deuterium oxide. D2O as opposed to H2O
What do you mean "no cigar"? Heavy ice is frozen heavy water. I know that it sinks in tap water. I stated "heavy ice" so as not to actually give it away.
Deuterium oxide. D2O as opposed to H2O
Cheers
It worked - you fooled me. I think the 'LOL' threw me. Sorry. Have a cigar!
Sorry about that, i was semi joking ( leveraging off the heavy ice comment )
Being a Mech engineer, i knew they had to be of different densities, but didnt know you could actually buy "heavy water".
How about letting those who have to get the thinking caps on have their bit of fun?
).
I think the 'LOL' threw me. Sorry. 
Have a cigar!
