MASTER THERMOCHEMISTRY Part 2 of 4

MASTER THERMOCHEMISTRY Part 2 of 4

PRESSURE-VOLUME (PV) WORK

source: CHEM112Queen's University

^What to catch from the above slide:

Pay attention to the formula that is written in blue, especially "w = -PΔV" --> this is one of the formulas you must know to answer questions on the exam.

1st FORMULA YOU NEED TO KNOW

The negative (-) sign is due to the system doing work on the surrounding

(ie whenever we do work on environment, we are using up energy!)

w = work

P = pressure

ΔV = change in volume

FIRST LAW OF THERMODYNAMICS

source: CHEM112 Queen's University

^What to catch from the slide:

1st law of thermodynamics is "energy is neither created nor destroyed during chemical or physical processes"

Whenever the system GAINS heat or energy from work, it is assigned a positive (+) sign.

Whenever the system RELEASES heat or energy doing work, it is assigned a negative (-) sign.

2nd FORMULA YOU NEED TO KNOW:

ΔU = internal energy (= total kinetic and potential energy in the system)

q = heat energy

w = work

**note that q and w are interchangeable FORMS of energy.

**It is important to keep in mind that the value for internal energy may vary depending on the signs assigned to "q" and "w". Ensure that you apply the correct signs based on the questions given!

PRACTICE Qs ON INTERNAL ENERGY (U), HEAT (q) AND WORK (w)

source: https://ch301.cm.utexas.edu/worksheets13/thermo/internal-energy-work-heat-wkst-KEY.pdf

source: https://ch301.cm.utexas.edu/worksheets13/thermo/internal-energy-work-heat-wkst-KEY.pdf

ANSWER KEY

^WATCH THIS VIDEO ON INTERNAL ENERGY, HEAT, AND WORK TO IMPROVE YOUR UNDERSTANDING ON THE CONCEPTS

LIL' EXTRA: STATE FUNCTION

source: CHEM112 Queen's University

^What to catch from the above slide:

State function: function where the outcome relies solely on the initial and final conditions, and not the process (e.g. INTERNAL ENERGY IS A STATE FUNCTION)

Heat (q) and work (w) are NOT state functions as the process is taken into account