Isothermal
Moderators: Chem_Mod, Chem_Admin

 Posts: 101
 Joined: Sat Aug 17, 2019 12:16 am
Isothermal
What exactly does it mean for the expansion of a gas to be “isothermal”? How does this impact which equations we should use?

 Posts: 113
 Joined: Fri Aug 09, 2019 12:15 am
Re: Isothermal
The expansion of a gas is isothermal when the volume of a system changes with a constant temperature. It is best to use equations where volume and pressure change rather than temperature change.

 Posts: 120
 Joined: Sat Aug 17, 2019 12:17 am
Re: Isothermal
The word "isothermal" refers to a system being at a constant temperature. In these situations, it is best to use the equations that involve a change in volume and pressure.

 Posts: 35
 Joined: Mon Jun 17, 2019 7:24 am
Re: Isothermal
Isothermal refers to the constant temperature of a system. No heat is added or lost to the environment.

 Posts: 105
 Joined: Wed Sep 18, 2019 12:20 am
Re: Isothermal
Isothermal means that delta T = 0 and therefore delta U = nc(delta T) = 0. This does not mean that delta Q = 0.

 Posts: 212
 Joined: Wed Sep 18, 2019 12:18 am
Re: Isothermal
Isothermal means that there is a constant temperature and that delta U is also equal to 0
Re: Isothermal
If the expansion of the gas is isothermal, then this means the temperature remains constant and delta U = 0

 Posts: 103
 Joined: Sat Aug 24, 2019 12:16 am
Re: Isothermal
Celine 1F wrote:If the expansion of the gas is isothermal, then this means the temperature remains constant and delta U = 0
Could you explain why delta U would equal 0? I'm a little confused about the connection between temperature and delta U.

 Posts: 51
 Joined: Wed Feb 20, 2019 12:18 am
Re: Isothermal
Isothermal means constant temperature, or the change in temperature = 0. For the work equations, the irreversable expansion equation can be used, which is W =  P external * deltaV.

 Posts: 95
 Joined: Sat Aug 24, 2019 12:15 am
Re: Isothermal
Abby Soriano 1J wrote:Celine 1F wrote:If the expansion of the gas is isothermal, then this means the temperature remains constant and delta U = 0
Could you explain why delta U would equal 0? I'm a little confused about the connection between temperature and delta U.
Delta U = 0 because the temperature of the system is not changing, meaning that the energy lost from the system through doing work is regained by energy from heat which is where we get the equation q = w

 Posts: 105
 Joined: Wed Sep 18, 2019 12:15 am
Re: Isothermal
Isothermal means there is a constant temperature present in the system, therefore, the most ideal equations to use would be the ones that include a change in volume or pressure

 Posts: 112
 Joined: Sat Jul 20, 2019 12:16 am
Re: Isothermal
Abby Soriano 1J wrote:Celine 1F wrote:If the expansion of the gas is isothermal, then this means the temperature remains constant and delta U = 0
Could you explain why delta U would equal 0? I'm a little confused about the connection between temperature and delta U.
We know that delta U= q + w and delta U=(3/2)nR(deltaT)
if delta T=0 then you are multiplying the constants in the 2nd equation by 0, thus you end up with delta U= 0
if delta U= 0 then you can plug the zero into U= q + w to get:
0= q + w
therefore q=w

 Posts: 125
 Joined: Sat Aug 17, 2019 12:17 am
Re: Isothermal
Emily Chirila 2E wrote:Abby Soriano 1J wrote:Celine 1F wrote:If the expansion of the gas is isothermal, then this means the temperature remains constant and delta U = 0
Could you explain why delta U would equal 0? I'm a little confused about the connection between temperature and delta U.
We know that delta U= q + w and delta U=(3/2)nR(deltaT)
if delta T=0 then you are multiplying the constants in the 2nd equation by 0, thus you end up with delta U= 0
if delta U= 0 then you can plug the zero into U= q + w to get:
0= q + w
therefore q=w
I understand the process above, however, isn't q = cmdeltaT, so as it is isothermic, delta T is equal to zero, so q is equal to zero?

 Posts: 29
 Joined: Mon Jan 06, 2020 7:57 am
Re: Isothermal
An isothermal process is a change of system where the temperature remains constant. Therefore, delta U would be equal to 0.

 Posts: 111
 Joined: Wed Sep 18, 2019 12:18 am
Re: Isothermal
Jessica Kwek 4F wrote:An isothermal process is a change of system where the temperature remains constant. Therefore, delta U would be equal to 0.
I agree with this, for example, in pizza rolls review session they showed how when t = o, delta U = 0, therefore q = w, which can come in useful knowing some of the types of questions that would be on the midterm

 Posts: 105
 Joined: Thu Jul 11, 2019 12:15 am
Re: Isothermal
along with isothermal, i think we also need to isobaric (constant pressure) and isochoric (constant volume)

 Posts: 112
 Joined: Sat Jul 20, 2019 12:16 am
Re: Isothermal
Nicholas_Gladkov_2J wrote:Emily Chirila 2E wrote:Abby Soriano 1J wrote:
Could you explain why delta U would equal 0? I'm a little confused about the connection between temperature and delta U.
We know that delta U= q + w and delta U=(3/2)nR(deltaT)
if delta T=0 then you are multiplying the constants in the 2nd equation by 0, thus you end up with delta U= 0
if delta U= 0 then you can plug the zero into U= q + w to get:
0= q + w
therefore q=w
I understand the process above, however, isn't q = cmdeltaT, so as it is isothermic, delta T is equal to zero, so q is equal to zero?
If there is no change in temp, you calculate q using q=m(deltaH)
Think about the heating curve graph where there is a horizontal line (phase change) we use q=m(deltaH), whereas when there is a change in temp, we use the equation you stated: q=cm(deltaT)
Return to “Calculating Work of Expansion”
Who is online
Users browsing this forum: No registered users and 1 guest