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Thermodynamics Topic 10 Sections 2 and 3 Thermodynamics Topic 10 Sections 2 and 3

Thermodynamics Topic 10 Sections 2 and 3 - PowerPoint Presentation

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Thermodynamics Topic 10 Sections 2 and 3 - PPT Presentation

Statement Number Assessment Statement 1021 Deduce an expression for the work involved in a volume change of a gas at constant pressure 1022 State the first law of thermodynamics 1023 Identify the first law of thermodynamics as a statement of the principle of energy conservation ID: 783193

energy gas processes work gas energy work processes system state internal volume constant temperature change pressure thermal ideal thermodynamics

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Presentation Transcript

Slide1

Thermodynamics

Topic 10

Sections 2 and 3

Slide2

Statement Number

Assessment Statement

10.2.1Deduce an expression for the work involved in a volume change of a gas at constant pressure10.2.2State the first law of thermodynamics10.2.3Identify the first law of thermodynamics as a statement of the principle of energy conservation10.2.4Describe the isochoric (isovolumetric), isobaric, isothermal and adiabatic changes of state of an ideal gas10.2.5Draw and annotate thermodynamic processes and cycles on P-V diagrams10.2.6Calculate from a P-V diagram the work done in a thermodynamic cycle10.2.7Solve problems involving state changes of a gas

10.2 Processes

(The First law of Thermodynamics

)

Slide3

By definition: The study of the conditions under which thermal energy can be transferred through performing mechanical work

Macroscopic Properties: Pressure, Volume and Temperature—all used to determine the amount of work that is/can be done by or to a sample of gas.

Thermodynamics

Slide4

Internal Energy:

The sum of the total kinetic energy of the molecules in a sample of a gas and the potential energy associated with the intermolecular forces with that gas.

Ideal Gases: assume that the intermolecular forces are non-existent, so potential energy = 0Therefore the internal energy is solely related to the kinetic energy (which is random…each molecule is likely different)Average Kinetic Energy:  Internal Energy

Slide5

Internal energy of a fixed quantity of a gas (constant number of moles) will only depend on the

temperature

. It does NOT depend on volume or pressureFree-Expansion: when a gas is allowed to expand in a way that is not constricted—both the volume an pressure change in such a way that the temperature will remain constant (in an ideal gas)Thus—the internal energy is constant for a given temperature of ideal gas.Internal Energy

Slide6

The complete set of objects being considered in a particular scenario/problem

Open System

Mass is free to enter and/or leave the systemClosed SystemMass is not free to enter and/or leave the system. The quantity of the gas will remain constantIsolated SystemNo energy in any form can enter or leave the systemSystems

Slide7

The

State

of a system is known when particular quantifiable characteristics of the system are known, such as the following:PressureVolumeTemperatureInternal EnergyState Function: a characteristic of the system.If two gases, originally in different (thermodynamic) states, are brought to the same state, the gases will have the same internal energy—no matter how they got there.State of a System

Slide8

Thermal Energy and

Work

Doing work, or adding or removing thermal energyRelated to a CHANGE in the state, not in the state itselfA gas does not “contain” thermal energy—it can transfer it when it changes stateA gas does not “contain” work—it has work done to it when compressed, or work done by it when expandedNon-state functions

Slide9

Work Done by/to a Gas

Imagine a Piston—cross sectional area

AChange the position of the piston by applying a force to expand or compress the gas Volume changesW = P·ΔV

Slide10

PV diagrams

Slide11

PV Diagrams

Total work done by the gas as it expands (or to the gas as it’s compressed) = area under the curve

Closed loop? Total (net) work done to/by the system = enclosed area

Slide12

Those processes in which the

pressure

of the system remains constant while the volume and temperature changeResults in a horizontal line on a PV diagram (Isobar)Isobaric Processes

Slide13

Those processes in which the volume remains constant while the pressure and temperature change

Results in a vertical line on the PV diagram (an

Isochore)No work is done during an isochoric processIsochoric Processes

Slide14

Those processes in which the temperature remains constant (and, as a result, the internal energy)

The pressure and volume will each change

Isothermal Process

Slide15

Thermodynamic Processes are any processes that will result in the change of the state of a system

Heating a gas

Compressing the gas (doing work TO the gas)Expansion of the gas (work done BY the gas)