What does it mean to never heat a closed system?

Question

In science, I have to make a poster about "never heat an enclosed system." but what exactly is an enclosed or closed? system.... like

I cant picture what to draw. a beaker with a cover?? but what does the cover look like..

can someone link an image or tell me the name of the thing so I can google it and find out what to draw...

Answer 1

Never heat a enclosed system is just that... I'm not sure why you wouldn't, but I suppose if it is producing gases that's an issue because pressure could build up. Have you ever heated water with the lid on, really, really hot? Something like that.

A closed system is basically where none of the products or reactants can escape.  

Answer 2

a closed system meaning Assassination. let me explain. we had this jamacian dood in my chem class and i was heating some mixture in a glass tube with a rubber cork. next thing i knew is i hit him in the head. in which i yelled out HEAD SHOT! LOL! yea i was heating a closed system...never do that.  

Answer 3

You should never heat a closed system unless it's been specifically designed to tolerate high pressures.  Pressure, temperature, and volume are all related (PV=nRT).  If you have a closed system (constant volume) and you increase the temperature, the pressure will increase along with it.  If your system can't handle the increased pressure, then it could rupture.

This happened to me once accidentally during my organic chem lab.  We produced ethanol with yeast and sugar water, and we were distilling the mixture to isolate the ethanol.  I had a flask on a hot plate (with the alcohol and water) hooked up to a condensation column (a tube with the alcohol vapor, running through a larger tube of cold running water), which sloped down and connected to a smaller connecting flask (see the link below).

Normally, the joints at the collection flask aren't air tight, so it wouldn't be a closed system, and could be heated with impunity.  There was something wrong with my setup, however.  Maybe there was some silicone grease left on the joint from the previous person to use the flask, or maybe I just assembled it too tightly.  In any case, the pressure in the apparatus grew to the point where the collection flask popped off with a little "poonk" sound.  The real damage happened when the pressure in the system *dropped.*  The alcohol/water mix had been at around 100C (above the boiling point of a water/alcohol mix), but it hadn't boiled since the system was pressurized.  When the pressure was released, the mix flash boiled, went up through the column, down through the condenser, and spewed the incredibly hot mix on my hand, which had just caught the collection flask.  Needless to say, not fun.

So, long story aside, you shouldn't heat a closed system that isn't designed to tolerate high pressures because it can explode.  In the link below, there's a simple diagram of the rig that I used.  Mine was a little different, though.  There was no vent to the fume hood, so the (accidental) tight seal on all of the joints made it a closed system.

Answer 4

For your poster, draw something along the following lines under normal conditions then add the effect of heat added to the system.

A 'Closed System' is one where the contents of the system like a gas or a liquid cannot escape under normal circumstances.

A sealed container, an Isolated Vessel, a stretch of pipeline closed off by valves at each end...etc.

When heat is applied, even heat from the sun, the molecules of the trapped substance increase in Kinetic Energy, their temperature rises and their volume TRIES to increase.

All of this causes an increase in internal pressure of the system.

With enclosed gases, the pressure increase is not as dramatic as with enclosed liquids. The gases can build up to very high pressures depending on the temperature increase.

With enclosed liquids however, because liquids cannot be compressed, just a few degrees increase in temperature will build up tremendous Hydraulic Pressure which will quickly result in a rupture in the system that, depending on the maximum pressure the system will withstand can be disastrous.

Pneumatic pressure of gases can also cause a rupture in the same way but will take longer to build up pressure. In both cases, if the fluid involved is flammable, and there's a heat source in the vicinity, the effects will be even more disastrous.

Any closed system should have a Pressure Safety Relief system incorporated.