Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Carolyn on 20/11/2008 05:05:11

Title: The heat required to change liquid to a vapor is called what?
Post by: Carolyn on 20/11/2008 05:05:11
Last week I took a class to prep me for a big state exam I have to take for our state license in air conditioning.  The following is one of the questions the instructor said would probably be on my exam, but he didn't give the answer and I can't find it in any of the 25 friggin reference books I have.  I'm sure it's probably a simple answer but I have a headache and quite frankly I'm tired of looking for it.  HELP!

The heat required to change liquid to a vapor is called _____________.

Would also like to know how much heat is required.

The correct answer will be greatly appreciated.
Title: The heat required to change liquid to a vapor is called what?
Post by: RD on 20/11/2008 06:10:25
Quote
heat of vaporization or heat of evaporation, is the energy required to transform a given quantity of a substance into a gas.
http://en.wikipedia.org/wiki/Enthalpy_of_vaporization


For water the heat of vaporisation is 2260 Joules per gram,
i.e. 2260 Joules of energy is required into convert 1 gram of (liquid) water at 100oC into 1 gram of water vapour (gas) at 100oC.
http://en.wikipedia.org/wiki/Heat_of_vaporization#Other_common_substances
Title: The heat required to change liquid to a vapor is called what?
Post by: Bored chemist on 20/11/2008 07:06:31
Is "latent" the word you are looking for?
Title: The heat required to change liquid to a vapor is called what?
Post by: Carolyn on 21/11/2008 19:41:30
Quote from: RD on 20/11/2008 06:10:25
Quote
heat of vaporization or heat of evaporation, is the energy required to transform a given quantity of a substance into a gas.
http://en.wikipedia.org/wiki/Enthalpy_of_vaporization


For water the heat of vaporisation is 2260 Joules per gram,
i.e. 2260 Joules of energy is required into convert 1 gram of (liquid) water at 100oC into 1 gram of water vapour (gas) at 100oC.
http://en.wikipedia.org/wiki/Heat_of_vaporization#Other_common_substances


Thank you RD.  I knew I'd be able to count on you to find the info I needed! 

.....now if I could just get you to come and take the test for me! [:D]
Title: The heat required to change liquid to a vapor is called what?
Post by: Carolyn on 21/11/2008 19:47:35
Quote from: Bored chemist on 20/11/2008 07:06:31
Is "latent" the word you are looking for?


YES!  That's it exactly.  I just took a practice test and that question was on it.  The answer was latent heat of vaporization.

Thank you BC.  Once you gave me the correct word I was able to find it in one of my numerous reference books.

...now if I only knew the maximum weight that a pump jack scaffold could support or the minimum height required for a toe board, I'd be able to wrap this practice test up!

Thanks again.