Phase change


Moderators: Chem_Mod, Chem_Admin

Riya Sood 4G
Posts: 160
Joined: Sat Aug 24, 2019 12:18 am

Phase change

Postby Riya Sood 4G » Sun Feb 02, 2020 11:25 am

is the delta H positive or negative when ice turns to liquid?

Suraj Doshi 2G
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

Re: Phase change

Postby Suraj Doshi 2G » Sun Feb 02, 2020 11:40 am

This phase change causes the change in enthalpy to be positive (delta H is positive).

MinuChoi
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

Re: Phase change

Postby MinuChoi » Sun Feb 02, 2020 12:48 pm

Enthalpy will be positive because the molecules must absorb energy to loosen forces on each other and assume more free form.

Dina Marchenko 2J
Posts: 54
Joined: Thu Jul 25, 2019 12:16 am

Re: Phase change

Postby Dina Marchenko 2J » Sun Feb 02, 2020 12:56 pm

A positive delta H means energy is put in (endothermic) which is what is necessary to break the bonds that holds a solid together into a liquid. That's why change in enthalpy is positive.

faithkim1L
Posts: 105
Joined: Fri Aug 09, 2019 12:17 am

Re: Phase change

Postby faithkim1L » Sun Feb 02, 2020 1:21 pm

Delta H should be positive.

John Liang 2I
Posts: 102
Joined: Fri Aug 30, 2019 12:18 am

Re: Phase change

Postby John Liang 2I » Sun Feb 02, 2020 1:27 pm

Because the phase change requires energy, there is a + delta H value. Hope this helps

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

Re: Phase change

Postby KHowe_1D » Sun Feb 02, 2020 1:31 pm

Delta H would be positive because the molecules are absorbing energy to "loosen" the bonds.

Callum Guo 1H
Posts: 134
Joined: Fri Aug 02, 2019 12:15 am
Been upvoted: 1 time

Re: Phase change

Postby Callum Guo 1H » Sun Feb 02, 2020 1:36 pm

Positive because you add energy

Naneeta Desar 1K
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

Re: Phase change

Postby Naneeta Desar 1K » Sun Feb 02, 2020 2:50 pm

Delta H is positive since melting is breaking bonds and energy is required in order to do so.

Celine 1F
Posts: 120
Joined: Fri Aug 02, 2019 12:16 am

Re: Phase change

Postby Celine 1F » Sun Feb 02, 2020 3:00 pm

In this case, delta H is positive

Abigail_Hagen2G
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

Re: Phase change

Postby Abigail_Hagen2G » Sun Feb 02, 2020 7:19 pm

It would be positive, because it requires energy to cause the phase change.

Isabella Dal Porto 1H
Posts: 100
Joined: Fri Aug 30, 2019 12:16 am

Re: Phase change

Postby Isabella Dal Porto 1H » Sun Feb 02, 2020 7:22 pm

Breaking the bonds that are holding the solid together requires energy. Thus, delta H is positive since the reaction is endothermic (needs energy/energy absorbed).

KSong_1J
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

Re: Phase change

Postby KSong_1J » Sun Feb 02, 2020 8:11 pm

Delta H is positive because energy must be used to break the bonds to turn ice into a liquid

Anish Natarajan 4G
Posts: 51
Joined: Thu Jul 25, 2019 12:16 am

Re: Phase change

Postby Anish Natarajan 4G » Sun Feb 02, 2020 10:11 pm

You're going from a state of lower energy to a state of higher energy when you go from a solid to a liquid (or a liquid to a gas) so the change in enthalpy should be positive

gconcha
Posts: 37
Joined: Fri Aug 09, 2019 12:16 am
Location: Sunset Village
Contact:

Re: Phase change

Postby gconcha » Sun Feb 02, 2020 10:13 pm

Because heat (energy) needs to be added to the ice in order to make it undergo a phase change into liquid form, is positive

Anushka Chauhan2B
Posts: 51
Joined: Sat Aug 24, 2019 12:16 am

Re: Phase change

Postby Anushka Chauhan2B » Sun Feb 02, 2020 10:40 pm

It should be positive

205389184
Posts: 100
Joined: Sat Sep 07, 2019 12:18 am

Re: Phase change

Postby 205389184 » Sun Feb 02, 2020 11:24 pm

Delta H would be positive when ice turns to liquid

Nare Nazaryan 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Re: Phase change

Postby Nare Nazaryan 1F » Sun Feb 02, 2020 11:48 pm

Delta H is positive when ice turns to liquid (applying heat to change from solid to liquid).

smurphy1D
Posts: 51
Joined: Mon Nov 18, 2019 12:18 am

Re: Phase change

Postby smurphy1D » Mon Feb 03, 2020 10:26 am

Delta H is positive because heat is being added in order to melt the ice

Madelyn Romberg 1H
Posts: 102
Joined: Tue Oct 02, 2018 12:16 am

Re: Phase change

Postby Madelyn Romberg 1H » Tue Feb 04, 2020 5:52 pm

Delta H is positive as the system absorbs energy in order to go to a liquid phase AND the energy remains there to keep it in a liquid phase.

Megan Kirschner
Posts: 46
Joined: Wed Feb 20, 2019 12:17 am

Re: Phase change

Postby Megan Kirschner » Wed Feb 05, 2020 9:32 pm

A positive delta H means energy is put in, which makes it endothermic, which is what is necessary to break the bonds that holds a solid together into a liquid. That's why the change in enthalpy is positive!


Return to “Concepts & Calculations Using First Law of Thermodynamics”

Who is online

Users browsing this forum: No registered users and 1 guest