Ch15 : Thermodynamics

Ch15: Thermodynamics Or, “Let’s try to remember all that stuff we learned last year, K!”

Seriously… • Whatsup? • Ch 13, 14, & 15 simultaneously • Regular HW each chapter. • DUE DATES?

Heat & Thermodynamics Ch 15 – Thermodynamics

Basic LAWS • 0th Law • Two systems individually in thermal equilibrium with a 3rd system are in equilibrium with each other. • Sorta like • If A=B & B=C, then A=C

Online Thermal Thing

Figure 15.3 WRONG! • The first law of thermodynamics is the conservation-of-energy principle stated for a system where heat and work are the methods of transferring energy for a system in thermal equilibrium. represents the net heat transfer—it is the sum of all heat transfers into and out of the system. is positive for net heat transfer into the system. is the total work done on and by the system. is positive when more work is done by the system than on it. The change in the internal energy of the system,, is related to heat and work by the first law of thermodynamics, .

Figure 15.3 • The first law of thermodynamics is the conservation-of-energy principle stated for a system where heat and work are the methods of transferring energy for a system in thermal equilibrium. represents the net heat transfer—it is the sum of all heat transfers into and out of the system. is positive for net heat transfer into the system. is the total work done on and by the system. is positive when more work is done by the system than on it. The change in the internal energy of the system,, is related to heat and work by the first law of thermodynamics, .

Basic LAWS • 1st Law • Internal energy of a system changes from an initial value Ui to a final value Uf due to heat Q and work W: • U = Uf – Ui= Q + W • Q>0 when system gains heat & <0 when it loses heat. • W>0 when work is done ON system & <0 when gas does work.

Basic LAWS • 1st Law • Internal energy of a system changes from an initial value Ui to a final value Uf due to heat Q and work W: • Q = Heat transferred to a system. • W = Work done ON a system

QIN > 0 QOUT < 0

WON > 0 WBY < 0

QIN > 0 QOUT < 0

WON > 0 WBY < 0

Using the 1st LAW • 2500J of heat is added to a system, and 1800J of work is done on the system. Find change in internal energy of the system?

Basic LAWS • 1st Law Example (p427) • T of 3 mol is reduced from 540K to 350K by adding 5500J of heat to it. • Find U & W done by or on gas.

T of 3 mol is reduced from 540K to 350K by adding 5500J of heat to it. • Find U & W done by or on gas.

T of 3 mol is reduced from 540K to 350K by adding 5500J of heat to it. • Find U & W done by or on gas. by or on gas?

Using the 1st LAW • Work done on or by a gas?

PV Diagrams

1st Law Thermal Processes • Isobaric • Constant P • W=PV • Isochoric (Isovolumetric) • Constant V • Isothermal • Constant T • Adiabatic • No transfer of heat

Thermal Processes • Isobaric Copied from Emile Clapeyron’s Bio (1799 - 1864).

Thermal Processes • Isochoric Copied from Emile Clapeyron’s Bio (1799 - 1864).

Thermal Processes • Isothermal Copied from Emile Clapeyron’s Bio (1799 - 1864).

Thermal Processes • Adiabatic Copied from Emile Clapeyron’s Bio (1799 - 1864).

Thermal Processes • Since W=PV, Work is area under P/V graph.

1st Law Thermal Processes • Isobaric • Constant P • W=PV • Isochoric • Constant V • Isothermal • Constant T • Adiabatic • No transfer of heat

Using the 1st LAW • Efficiency of a heat engine?

Using the 1st LAW • Ideal efficiency (Carnot Engine)?

Carnot (IDEAL) Engine

Basic LAWS • 2nd Law • Heat flows from a substance at higher temp to a substance at lower temp and does NOT flow in the reverse direction. Ever.

Basic LAWS • 2nd Law & Entropy • Entropy, disorder or randomness, of the Universe increases

Basic LAWS – 2nd • The total entropy of a system PLUS the environment increases as a result of heat flow.

Basic LAWS • 3rd Law • Absolute Zero is impossible to reach in a finite number of steps.

Ch 13-15 • HW Posted. • PSS next 1-2 classes

Ch15 : Thermodynamics