POSTED by: Scott McKittrick on 09/30/2009
Microgravity (aka weightlessness), it is a condition that causes all sorts of interesting phenomena…like bubbles that sit in water without floating.
The reason that bubbles float on earth has to do with the relative density of water compared to air. At sea level, water is 784 times denser than air and so gravity pulls it down towards the earth more than it does air, thus the air rises out of the water. Perhaps a more accurate way to see it would be to say that the water sinks. In microgravity, such as being on the space shuttle in orbit, there is no gravity to pull harder on the water than on the air, so the air has no reason to rise and ends up staying in the middle of the water. NASA has put together some very interesting videos on the behavior of water and bubbles in space. See them here.
Difference in density also explains why steel sinks but wood floats. For information on why steel boats float instead of sink, see Bouyancy.
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POSTED by: Scott McKittrick on 08/13/2009
This week will be the last Science Friday workshop that Lorenzo and I do before taking a break to deal with the back to school rush. As such we want to go out with a bang and some of our experiments will actually do so.
One of the experiments that we are going to do deals with sodium acetate, an industrial byproduct commonly used in reusable hand warmers. It would be easy enough to go get some hand warmers and cut them open, but I decided to try making some myself first, if only to say that I had. I cooked the ingredients over a camp stove in an old coffee can as I couldn’t positively say that the experiment wouldn’t mess up my mom’s pots. The picture above shows the solution as I as boiling it down.
So far my attempts have failed, though this might have had to do with the fact that I miss measured the baking soda. I will try again tomorrow.
Related Links:
About.com – How to make Hot Ice
The Thematic Attic
Update:
It took me three tries, but I got a batch that seems to work. Unfortunately, it crystallized while cooling, so I had to melt it down again. Hopefully, it will still be good when it cools.
Update Again:
I remelted the sodium acetate that I had and it didn’t work after that. So Science friday went on without it. We did some stuff with baking soda and vineagar as well as Alka-Seltzer rockets. It was still a success.