I agree that this is an odd term. I think it refers to liquid phase as being "saturated" with thermal energy. If you add heat at constant pressure, the temperature of the liquid phase does not increase. The liquid has all the thermal energy it can hold at that pressure.

When it's boiling, the water is cooling but does that mean the space above is getting warmer?

So glad it worked. Science!

Glad to hear it was helpful

no

It will remain saturated until the triple point (about 0.01C).

Yes. It sets off at the normal boiling point (100C, 212F) at atmospheric pressure, and cools to about 50C (120F), still boiling because the pressure drops in the jar.

Thermal energy.

Unfortunately, no. The condensation rate is too low at room temperature.

The pressure in steam tables is absolute pressure. A gauge pressure of 2 atm corresponds to an absolute pressure of 3 atm (if local atmospheric pressure is ~1 atm). At this absolute pressure, the saturation temperature ("boiling point") is about 134 C (not 120 C).

Thanks David. I see... So if I heat the water to above 135 C and get it boiling, would I see an increase in the pressure of the system? As in, does the boiling vapor "add" more pressure?

Yes. If you have saturated water at 3 atm (134C) in a sealed jar and you add heat, the pressure will increase. Have you taken a thermodynamics course? If so, this process is a vertical upward line on a T-v diagram. This is a constant specific volume process. Hope that helps. (Also, remember the physical cause of pressure: It is the force produced by water molecules bouncing off the container walls. More heat means more molecular kinetic energy, means more impact force, and thus, higher pressure on the walls.)

I see! That makes sense. I have done a subject on thermodynamics but never really understood it well, but thanks for pointing that out! at least now I know where to do further reading (T-V diagrams). Thanks again for your replies. It's really helped

Immediately after putting on the lid, the liquid and vapor are a equilibrium at saturation conditions, 1atm and 100C. As the water cools the pressure will fall. But the cooling process is slow enough (without the ice) that the system will be very close to equilibrium. For example, if you measured the liquid temperature before putting on ice -- say, it was 95C -- you could look up the corresponding pressure on a saturation table (84.6kPa). This would be very close to the actual pressure in the vapor in the top of the jar. (I've thought about adding a Bourdon gage on the lid to demonstrate this.) Of course, the system is not at perfect equilibrium, since there is some vapor condensation on the glass and lid without the ice. But it would be close.

The timing of the ice should not matter. However, it is critically important not to let air into the jar. Even a small amount of air will greatly reduce the condensation rate on the lid, and reduce the tendency to boil. So, differences in the haste and care in putting on the lid can produce a lot of variability. That may be what you are seeing.

Yes, I think so, though it is probably not water.

Boiling doesn’t mean increasing the temperature. Boiling starts, when vapour pressure of the liquid becomes equal to the atmospheric pressure. Boiling can occur at 20 degree celsius also.

No. This process does not break chemical bonds.

I'd say about 60 to 90 seconds if sufficient. The air needs to be almost completely replaced by water vapor. The presence of any air greatly reduces the heat transfer rate to the lid, and reduced the effect.

tacobell

Hmmm... what could go wrong? Try it again and be extra careful to get all the air out of the upper part of the jar. Don't poke many holes in the cling film and let it boil for a couple of minutes. Then get the lid on FAST. For technical reasons that I can't go into here, you need almost pure water vapor in the upper space. Even a bit of air will reduce the condensation rate tremendously and may prevent vigorous boiling. Hope that helps.

@@FluidMatters Thank you so much, sir, you're my lifesaver huhuhuhu