Archives of Ask A Scientist!
About "Ask A Scientist!"
On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.
Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.
So now we are down to 0.25 atmosphere. But oxygen isn't an ideal - gas and can liquefy. At one atmosphere pressure, the temperature at which it liquefies is about 90K.
As the temperature decreases, the pressure at which a gas liquefies becomes lower. The relationship between temperature (in Kelvin) and pressure isn't linear, so you have to look up the pressure for a particular temperature in a table. It turns out that at a quarter of an atmosphere, the temperature at which liquid oxygen forms is 78.77 K, or a little higher than that of liquid nitrogen at one atmosphere pressure.
So now what? Well, the answer is that some of the oxygen will liquefy, occupying a much smaller volume, and the pressure will fall some more till it gets down to the pressure at 77K (roughly 1/5 of an atmosphere). Then the liquefaction will stop.
So if you pressurized a balloon to an atmosphere pressure (the pressure inside and the pressure outside are equal) then the pressure inside will drop to 1/5 of an atmosphere (which is the pressure above the liquid oxygen at 77K), the balloon will wrinkle up and liquid oxygen will collect in a pool at the bottom of the balloon. If you started with a high pressure of oxygen (blew up the balloon even more) then you'd have the same pressure inside but more oxygen liquid at the bottom of the balloon (and the balloon would wind up being more or less the same size in either case). The pressure difference (between the 1/5 atmosphere inside and the 1 atmosphere outside) is then supported by the balloon's walls because the balloon has "stiffened" as the rubber freezes up.
- I know that water can put out a fire. What does liquid nitrogen do to a fire?
- How do underwater flares and torches work, when water puts out fires?
- How do you make a computer game?
- How are dryer sheets manufactured?
- If you burn a liter of fuel in an internal combustion engine are the emissions the same weight as the weight of the original liter, if not why?
- Why is gold such a soft material compared to something like iron?
- How do scientists know there are such things as atoms?
- Why is the pressure required for a bicycle tire so much higher than the pressure for a car tire? How come the much smaller bike tire does not explode when filled with such high pressure?
- Can we ever make nuclear powered cars in the future?
- What exactly are isotopes? I know that an element with different proton and neutrons is an isotope. So would it mean that (for example) Barium is an isotope but Aluminum is not?