Chemistry Challenge Involving Water

Hello,

I have been working on an idea for a class room model that would illustrate 2 topics of education: water cycles and liquid properties. The goal would be to place water in a chamber or series of chambers and apply a vacuum to lower the boiling temperature. A heat source less than 212 degrees F would be applied to boil the water and show the relationship between pressure and temperature and water phases. The water vapor would then condense and return to a liquid form and begin the cycle again demonstrating the water cycle. Research on this subject leaves me with two questions that I have been stuck on for over a week:

1. All examples I have found show applying a continuous vacuum to the apparatus in order to keep the pressure low when water vapor is being created. Is there any way to create a vacuum chamber and then ‘cap’ the system so it is self-contained and does not require leaving a vacuum pump running? What if the initial pressure was so low that the water vapor created did not increase the pressure significantly? What about mechanically expanding or compressing the chamber?

2. I have read about ‘de-gassing’ a liquid in a vacuum and my understanding of this is when the soluble air particles in the water are pulled out. This creates the appearance of boiling but it is deceptive and only lasts about 60 seconds. Once this stops, if the temperature is raised and the pressure is lowered will the water ‘boil’ or does degassing prevent boiling from happening?

I appreciate all of your help on this subject. Chemistry was never my strong point in school and I am attempting to work with what little knowledge I have.

 

Log in or Sign up to hide all adverts.

Apply an initial vacuum to a vessel large enough that the volume of the steam produced has a relatively small effect, ie use the biggest vessel you can find.

No, as you said degassing is simply the removal of dissolved gases in the water. Once that's gone, you can still boil the water. Boiling is the transition between liquid water and gaseous water.

Hope this helps!

 

Log in or Sign up to hide all adverts.