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 • 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 Amt of energy absorbed
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 O28 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 O28 CO2 +10 H2O) Given: 65 grams of butane : H reaction = 5315 kJ Find moles (n) of butane Find molar enthalpy n= 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