Melting Ice In A Vacuum

You won't get a vacuum..some water & water vapour will fill the space.

NO- with caution, I made the assumption that this was a solid block of ice.

If you use the same container for both a vacuum and non vacuum experiment, It will have the same surface area for both and the same conduction of heat. the small amount of vacuum may cause some sublimation of ice into vapor. That should have no measurable effect on the melting of ice.

The melting starts with the container being 100% full of ice, right? So all of the container surface area is in contact with the ice and the outside surrounding atmosphere. The outer surface of ice melts first and continues the contact with the containers. It is not until a healthy percentage of the ice is melted that you will get some discontinuity with the water and the inner surface of the container. By then humidity or water vapor will take up the space and continue the heat transfer into the ice to melt it.

Are you removing all air from the water before freezing?

Is it a solid block of ice or it is "cubes" with space around them?

First, I fill the tube (about 5 in. long and 0.75 in. diameter) with water from the tap. Then I freeze it without the cap. When frozen, I remove the extra ice that pushed up above the tube and put the cap on. With that procedure, I make sure the ice is a solid block.

But if the is air INTO the water, how can I remove it before freezing?

Would the fact of removing it slower the melting process?

The difference in volume between the ice and the water into which it melts is pretty small and the vapour pressure of the water vapour at 0°C is quite high so all in all this is a pretty lousy way to try and produce a vacuum.

Boil the water first, then freeze it to keep the bubbles out.

Or, if you have a vacuum chamber handy, fill a cup full of water, place it in the chamber and pump it down. As the pressure approaches the vapor pressure of water, the water in the cup will boil. Continue boiling the water in this way until it freezes (you can also do this with liquid nitrogen to make frozen nitrogen. Really!)

that's how they make instant coffee

TAKE A PET COKE 1.5 L BOTTLE. PUT WATER INTO IT FILL IT TO BRIM. NEXT FREEZE IT AFTER FREEZING REMOVE ANY ADDITIONAL ICE ON THE NECK. CAP IT TIGHTLY. NEXT KEEP THE BOTTLE IN OPEN AMBIENT CONDITION. AS ICE MELTS SOME SQEEZING OF BOTTLE SHAPE WILL PERHAPS HAPPEN?

REGARDS

ARUN JALALI

In the case of a plastic bottle no vacuum will be generated. The pressure in the bottle will be close to atmospheric ambient, accompanied by deformation of the bottle to maintain that pressure.

Here's a link to an experiment I did in an earlier life. If I recall, (I don't) I think that ten atmosphere's pressure reduces the melting temp by 1/10 degree F. Therefore, reducing pressure should raise the melting temp, probably causing the rate to decrease.

→ Steam Tables.

As the ice melts some water vapour will occupy the space above the ice. The pressure of the water vapour, and hence the absence of vacuum, will depend only upon the temperature. An equilibrium will be approached at that temperature. An adiabatic system will change its temperature slightly to accomodate the equilibrium. An isothermal system will approach an equilibrium determined by the temperature.

The melting rate is determined by the rate of input of heat to the ice/water/vapour system and its effect is to drive the system towards a new equilibrium point where solid ice is not present.