Ch 6 Thermodynamics

# Ch 6 Thermodynamics - Ch 6 Thermodynamics A 6.2 the nature...

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A. 6.2 the nature of energy: key definitions a. thermochemistry : study of relationship b/w matter + energy a.i. energy : the capacity to do work a.i.1. energy can be transferred thru heat flow of energy caused by a temperature difference a.i.2. heat + work ways that objects exchange energy a.ii. work : a force acting over a distance a.iii. potential energy : energy stored due to position or composition (in chemical bonds) a.iii.1. chemical: PE stored in bonds, associated w/ positions of e- + nuclei a.iii.2. nuclear: PE of atomic nuclei a.iv. kinetic energy : energy due to motion of an object a.iv.1. thermal (heat): KE associated w/ temperature a.iv.2. electrical: KE associated w/ flow of electrical charge a.iv.3. light: (radiation) KE of electronic transitions in an atom a.iv.4. ; m=kg, V=m/s; 1 kg( 2 = 1 Joule ; 1 kcal = 4184 J b. 1 st law of thermodynamics/law of conservation of energy : energy can’t be created nor destroyed, but can be transferred between a system and its surroundings; total energy of universe is constant; energy can be transformed from one form to another b.i. system : any defined environment b.ii. surroundings : everything else (rest of universe) with which the system can exchange energy b.iii. system + surroundings = universe c. Units of energy: c.i. Joule (J) = energy needed to move 1 kg mass 1 m; 1J = 1 Newton meter or 1 kg m 2 /s 2 c.ii. calorie (cal) —energy needed to raise 1 g of water 1 °C ( 1 cal = 4.184 J ) c.ii.1. kcal energy needed to raise 1 kg of water 1°C c.ii.2. food calories =kcal c.iii. kilowatt-hour (kWh) —used to measure electrical energy (1 kWh = 3.6x10 6 J) B. 6.3 The First law of Thermodynamics: a. 1 st law : total energy of universe is constant b. Internal Energy (E) of a system = sum of KE + PE of all particles in system b.i. Δ in internal energy (ΔE) = +pos if system absorbs energy (if system gains energy from surroundings) b.i.1. +ΔE sys = -ΔE surroundings b.i.2. -ΔE sys =+ΔE surroundings b.i.3. ΔE reaction = E products – E reactants b.i.4. ΔE = E final - E initial

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Ch 6 Thermodynamics - Ch 6 Thermodynamics A 6.2 the nature...

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