Holi, Hindu Festival of Colours

ThermodynamicsTuesday, 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▫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

Net amt of energy released

Amt of energy absorbed

Transition state

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

: H reaction = 5315 kJ

Find moles (n) of butane Find molar enthalpyn= m/mm 5315 kJ ÷ 2 mol C4H10 = 2657.5 kJ/mol = 65g ÷ 58.14g/mol = 1.12 moles Plug into equation

Q= n * ΔH = 1.12 mol * 2657.5kJ/mol = 2976.4 kJ