Thermodynamics

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Slide 1

Thermodynamics

Courtesy of lab-initio.com

Slide 2

Definitions #1

Energy: The capacity to do work or produce heat

Potential Energy: Energy due to position or composition

Kinetic Energy: Energy due to the motion of the object

Slide 3

Definitions #2

Law of Conservation of Energy: Energy can neither be created nor destroyed, but can be converted between forms

The First Law of Thermodynamics: The total energy content of the universe is constant

Slide 4

State Functions depend ONLY on the present state of the system

ENERGY IS A STATE FUNCTION

A person standing at the top of Mt. Everest has the same potential energy whether they got there by hiking up, or by falling down from a plane 

WORK IS NOT A STATE FUNCTION

WHY NOT???

Slide 5

E = q + w

E = change in internal energy of a system

q = heat flowing into or out of the system

-q if energy is leaving to the surroundings

+q if energy is entering from the surroundings

w = work done by, or on, the system

-w if work is done by the system on the

surroundings

+w if work is done on the system by the

surroundings

Slide 6

Work, Pressure, and Volume

Expansion

Compression

+V (increase)

-V (decrease)

-w results

+w results

Esystem decreases

Work has been done by the system on the surroundings

Esystem increases

Work has been done on the system by the surroundings

Slide 7

Energy Change in Chemical Processes

Endothermic:

Reactions in which energy flows into the

system as the reaction proceeds.

+ qsystem - qsurroundings

Slide 8

Energy Change in Chemical Processes

Exothermic:

Reactions in which energy flows out of the system as the reaction proceeds.

- qsystem + qsurroundings

Slide 9

Calorimetry

The amount of heat absorbed or released during a physical or chemical change can be measured, usually by the change in temperature of a known quantity of water in a calorimeter.

Slide 10

Units for Measuring Heat