Heat, Pressure, Volume, Work
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Heat, Pressure, Volume, Work
In lecture, Professor Lavelle explains how the molar heat capacity of a gas is different at constant volume and constant pressure because work is being done in one situation and not the other. What is the relationship between heat, pressure, volume, and work?
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Re: Heat, Pressure, Volume, Work
If pressure is constant and heat increases, then volume increases, and work is being done. If volume is constant and heat is added, then pressure increases but no work is being done.
Re: Heat, Pressure, Volume, Work
we can think of the relationship in terms of the equation PV = nRT. If temperature increases and pressure is constant, volume must increase. When the volume increases, the gas must move the particles in that extra space out of its way, which means that the gas is performing work (losing energy). If volume is constant, pressure must increase. One way pressure can be increased is if new molecules (like helium) are introduced. We learned that introducing another nonreactive molecule does not affect the reaction. In this second situation there is no work being done.
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Re: Heat, Pressure, Volume, Work
In terms of PV = nRT, n are R will be constant values in these types of situations. If we make either P or V constant, then the change of T will indicate the change of P/V (whichever is not constant).
Re: Heat, Pressure, Volume, Work
In order to determine the relationship between heat, pressure, volume, and work, you would use the equation PV=nRT. In that equation n and R are constants. Suppose P or V were constants, then an increase in temperature will result in the change in either P or V. You would have to use that equation in order to determine the changes when one variable increases or decreases.
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