Holi, Hindu Festival of Colours
Thermodynamics
Tuesday, March 2nd
Miss Tee
Introduction
• Living organisms are in constant struggle for
survival
▫ Grow and strengthen body
▫ Protect self from destruction (environment,
predators)
▫ Reproduce
• All this takes work!
• Must continually capture, store and use energy
What is energy??
The ability to do work
Through an elaborate series of highly controlled
chemical reactions, cells manage the materials
and energy they use to keep themselves alive.
Kinetic Energy
• Energy possessed by moving objects
▫ Raindrops falling
▫ Heart muscle contracting
• Many forms
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Thermal energy
Mechanical energy
Electromagnetic energy
Electrical energy
Potential energy
• Stored energy
▫ Because of an object’s position in an attractive or
repulsive force
• Different forms
▫ Gravitational potential energy
▫ Chemical potential energy
Gravitational Potential Energy
• The diver did not always have this potential energy.
He gained it because his muscles did work to lift
him to his position.
Potential to Kinetic Energy
• Objects will gain kinetic energy
and lose potential energy as
they fall to Earth
1st Law of Thermodynamics
• The total amount of energy in the universe is
constant.
• Energy cannot be created or destroyed.
• If an object or process gains energy, it does so at
the expense of a loss of energy elsewhere.
Bond Energy
• When atoms form bonds, their valence electron
configuration is stable.
• Some chemical bonds are more stable than
others.
• Bond energy: measure of the bond stability
Bond Energy
• In a chemical reaction:
▫ bonds between reactant molecules must be broken
▫ bonds between product molecules must form
• Energy required to break reactant molecules’
bonds = activation energy
Chemical Potential Energy Diagram
Net amt of energy released
Chemical Potential Energy Diagram
Transition state
Net amt of energy released
Entropy
• Entropy = measure of randomness or disorder in
a collection of items
• Entropy increases when disorder increases
▫ Deck of cards
Entropy
• In biochemistry, entropy increases when:
▫ Solids become liquids
▫ Liquids become gases
▫ Complex molecules react to form simpler
molecules
• The universe favours chaos.
▫ Do things spontaneously become organized? Does
your room tidy itself?
In general…
• When energy is changed from one form to
another, some is lost as heat
• Therefore, all changes result in increased
entropy (overall disorder) of the universe
2nd Law of Thermodynamics
• The entropy of the universe increases with any
change that occurs.
Enthalpy
• Enthalpy = measure of the internal energy of a
system
• If outside pressure on a system is held constant,
Δ enthalpy means Δ in system’s internal energy,
plus a change in system’s volume
▫ …meaning the system exchanges energy with the
outside environment
Think, Pair, Share
• Read: “Treatment of deep frostbite with
hyperbaric oxygen”
Think, Pair, Share
• How is the phenomenon of frostbite consistent
with the 1st and 2nd Laws of Thermodynamics?
Think Critically
• “Thinking is skilled work.”
• Does not mean simple criticism
▫ It means not simply accepting information at face
value
Think Critically
• Check the source. Who wrote thejournal
article?
• Check the date. Generally speaking, the more
recent the material, the more accurate the info.
• Always look for evidence.
• Be ready to change your mind if the
evidence changes.
• Beware of making assumptions.
• Look for cause and effect.
Think Critically
• The word 'why?' is the most powerful tool in
your mental toolbox.
• Frostnip can be treated at home. If you think you may have
frostnip, get out of the cold as soon as possible. Immerse the
affected area in warm water (100º to 105º Fahrenheit) to thaw
the frozen tissue. (Do not use hotter water, as this may burn your
skin.) If warm water is not available, warm the affected area with
body heat. For instance, warm your hands by tucking them into
your armpits; warm your nose, ears, or face by covering them
with dry hands.
• CAUTION! Do not rub the affected area because this may
increase damage to the tissue. Do not use a heating pad, heat
lamp, stove, fireplace, or radiator to rewarm the affected area;
these may warm your skin unevenly or may burn your skin,
particularly if it's numb and you cannot tell how hot your skin is
getting on the surface. If the skin tingles and burns as it warms,
circulation is returning. The skin may turn red but should not
blister or swell.
• Frostbite requires emergency medical care.
• CAUTION! If the affected area might be refrozen before you get
medical help, do not warm it; this greatly increases the risk of
damage. Also, do not walk on frostbitten feet or toes unless
absolutely necessary. At the hospital, frostbite is usually treated
comprehensively because its severity cannot be diagnosed in the
first few days. Usually, patients need to be admitted. Initially, the
hospital staff will probably do the following:
▫ Rapidly warm the affected area in water for 15 to 30 minutes.
▫ Remove blisters that contain clear or milky fluid, and cover
them with aloe vera. (Blisters that contain blood may not be
removed.)
▫ Splint and elevate the affected area; wrap it in a loose bandage.
▫ Administer ibuprofen to limit inflammation, tetanus toxoid to
prevent tetanus infection, and penicillin to prevent other
infection. Narcotic medication may be needed to treat pain as
the sensation to area returns.
▫ Later hospital treatment may include whirlpool therapy and
physical therapy to promote circulation. Surgery, including
amputation of the affected area, is sometimes necessary.
Amputation is performed only if the tissues are dead. This
determination is typically made 3-6weeks after the injury.
Enthalpy
• To calculate heat absorbed or released in a
system:
▫ Q= n * ΔH
Enthalpy
What is the molar enthalpy of CO2 (g) in the
reaction for the burning of butane below?
2 C4H10 +13 O2  8 CO2 +10 H2O
H=-5315 kJ
• Answer: Molar enthalpy is the enthalpy change
in equation divided by the balance of CO2
Molar enthalpy, H substance = 5315 kJ ÷ 8 mol = 664 kJ / mol
Enthalpy
• How much heat will be released if 65 grams of butane is
burned in a lighter according the equation in the example
before?
▫ (2 C4H10 +13 O2  8 CO2 +10 H2O) Given: 65 grams of butane
kJ
Find moles (n) of butane
n= m/mm
kJ/mol
= 65g ÷ 58.14g/mol
= 1.12 moles
: H reaction = 5315
Find molar enthalpy
5315 kJ ÷ 2 mol C4H10 = 2657.5
Plug into equation
Q= n * ΔH
= 1.12 mol * 2657.5kJ/mol