Ideal gas Assumptions 1.Particles that form the gas have no volume and consist of single atoms. 2.Intermolecular interactions are vanishingly small.

Ideal gas

• Assumptions1. Particles that form the gas have no volume

and consist of single atoms.2. Intermolecular interactions are vanishingly

small.

Ideal gas

Equations of statePV=NkTP= pressureV= volume N=number of particles of gask= Boltzmann Constant= 1.38x10-23J/KK=Kelvin temperature

Ideal gas

Equations of statePV=nRTP= pressureV= volumen=number of moles of gasR= Universal Gas Constant= K=Kelvin temperature

8.31J

mol K

Ideal gas

Avogadro’s number

236.022 10A

moleculesN x

mol

Ideal gas

Relationship between Avogadro’s number, Universal Gas constant, and Boltzmann constant.

AR k N

Kinetic –molecular theory

1. Many molecules are in a container and they behave like point particles.(No volume)

2. The molecules move around randomly, and obey Newton’s laws.

3. The only interactions that the molecules undergo are elastic collisions with each other and the walls of the container.

Kinetic –molecular theory

Pressure is a result of the molecules colliding with the walls of the container. As the number of molecules or thir average speed increases, the pressure increases.

Kinetic –molecular theory

Results of kinetic-molecular theory.

21 3

2 2

Kelvin temperature

avav

K mv kT

T

Kinetic –molecular theory

Results of kinetic-molecular theory.

3 3

Kelvin temperature

m= the mass of one molecule

M= the mass of one mole of molecules

rms

kT RTv

m MT

Kinetic –molecular theory

Internal energy of an ideal monatomic gas..

3 3

2 2Kelvin temperature

N= number of molecules

n= number of moles

U NkT nRT

T

Kinetic –molecular theory

Other gas laws – the amount of gas does not change

1 1 2 2

1 2

1 2

1 1 2 2

1 2

Boyle's Law - applies at constant temperature

P V =P V

Charles' Law - applies at constant pressure

Combined Gas Law

V V

T T

PV PV

T T

Laws of Thermodynamics

The first Law of Termodynamics –If U is the internal energy of a system, than DU=Q-W.

If Q>0 System gains heat

If Q<0 System loses heat

If W>0 Work is done by the system

If W<0 Work is done on the system

Laws of Thermodynamics

The first Law of Thermodynamics –If U is the internal energy of a system, than DU=Q-W

Table 18-1Signs of Q and W

Q positive System gains heat

Q negative System loses heat

W positive Work done by system

W negative Work done on system

Figure 18-1The Internal Energy of a System

Figure 18-2Work and Internal Energy

Laws of Thermodynamics

At constant pressure, the work done by or on a system is

W=PΔV

The area under a PV curve represents work. If a process occurs at a constant volume, the work done during the process is 0.

Figure 18-5A Constant-Pressure Process

Example 18-2Work Area

Laws of Thermodynamics

Isothermal processes – these are processes that take place at a constant temperature.

PV=constant

Figure 18-8Isotherms on a PV Plot

Laws of Thermodynamics

Adiabatic processes – these are processes that take place without heat entering or leaving the system.

During an adiabatic process Q=0 and

U Q W

U Q W W

Figure 18-9An Isothermal Expansion

Figure 18-10aAn Adiabatic Process

Figure 18-10bAn Adiabatic Process

Conceptual Checkpoint 18-2 Page 578Which is the adiabatic curve?

Figure 18-14A Comparison Between Isotherms and Adiabats