Re: Can we physically see oxygen?

Jim:

There are two easy ways that we can be able to "see" oxygen gas.  The 
first is to put the gas in a well insulated bottle, and cool the bottle to 
a very low temperature, when the oxygen in will begin to liquify.  This 
temperature is several hundred degrees below room temperature. If the 
liquid is inside a dewar flask, which means that the flask is very well 
insulated so the oxygen will stay cold there, you can look into the flask 
and see the liquid oxygen bubbling away.  It is a very pale blue color 
easy to see with your naked eyes.

This is very similar to the fact that you can see water inside a glass of 
water, but if you let the water get warm and evaporate into the air you 
cannot see it any more even though it is still there in the room with you!

The second way that you can easily see oxygen is to put the oxygen inside 
a vacuum-tight vessel at a very low pressure, and then initiate a plasma 
within the oxygen gas at low pressure.  In this plasma, electrical energy 
is being put into the oxygen molecules because they are being bombarded by 
energetic electrons, and this makes the oxygen molecules become excited 
and give off light!  In this case the light is a dull pink color because 
the molecules are excited and very hot, not like in the liquid oxygen 
where they are very cold and they look blue!

Jim, I hope this answer satisfies you.   These experiments are very simple 
to do, but the science behind them is very complicated!

Dick Bersin......