## Science

Published in: Physics
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### Ravikiran

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Thermodynamics and its princinples

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Thermodynamics
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Thermodynamics Developed during the 1800's to explain how steam engines converted heat into work. Thought Questions: Is heat just like light and sound? > Is there a "speed of heat"? Answer: Not rea//y.
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Structure of Matter Protons Atomic Number - number of protons Neutrons nuclear glue Electrons Valence Electrons - those far from the nucleus Atoms, Molecules, and a Lattice Amorphous - random arrangement of atoms Crystal - atoms are ordered in a lattice
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Temperature >Measured in Fahrenheit, Celsius, and Kelvin > Rapidly moving molecules have a high >Slowly moving molecules have a low
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Temperature Scales Boiling Point of Water Freezing Point of Water Absolute Zero Fahrenheit 212 w 32 OF -459 OF Celsius 100 oc ooc -273 oc Kelvin 373K 273K OK
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Pressure Pressure - force per unit area It has units of N/m2 or Pascals (Pa) Impact Weight
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Pressure >What are the possible units for pressure? 1 Pa = 1 N/m2 N/m2 Pasca I >atm psi >rnm Hg 1 x 105 Pa 1 atm = = 1 lb/inch2 1 psi 760 mm Hg 1 atm =
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Density > Density - mass per unit volume At has units of g/cm3 Low density High density
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States of Matter Solid Gas Liquid Plasma
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State of Matter Definitions Phase Diaqram Plot of Pressure versus Temperature Triple Point > A point on the phase diagram at which all three phases exist (solid, liquid and gas) Critical Point > A point on the phase diagram at which the density of the liquid a vapor phases are the same
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Gas Laws perfect (idea/ ) Gases Boyle's Law Charles' Law Gay-Lussac's Law Mole Proportionality Law
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Boyle's Law T = const n = const
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Charles' Law P = const n = const
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Gay-Lussac's Law V = const n = const
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Mole Proportionality Law T = const P = const
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Boyle's Law T = const n = const
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Charles' Law P = const n = const
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Gay-Lussac's Law V = const n = const
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Mole Proportionality Law T = const P = const
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Perfect Gas Law > The physical observations described by the gas laws are summarized by the perfect gas law (a.k.a. ideal gas law) PV = nRT = absolute pressure A/ = volume = number of moles = universal gas constant > T = absolute temperature
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Table : Values for R pa 1773 8.314 mol-K atm•L 0.08205 mol-K J 8.314 cal 1.987 Work Problem 11.8
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Volumes? Sphere > r3
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Work >Work = Force x Distance > The unit for work is the Newton-meter which is also called a Joule.
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Heat Capacity Defined mAT > Q - heat in Joules or calories > m - mass in kilograms AT - change the temperature in Kelvin > C has units of J/kg K or kcal/kg K 1 calorie = 4.184 Joules
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Heat Capacity > An increase in interna/ energy causes a rise in the temperature of the medium. Different mediums require different amounts of energy to produce a given temperature change
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Energy >Energy is the ability to do work. At has units of Joules. At is a "Unit of Exchange' Example I car = 1 f70LJSe = \$100k — cars = 1 house
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Energy Flow > Heat is the energy flow resulting from a temperature difference. Heat and temperature are not Note : the same.
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Heat Flow 1000c Temperature Profile in Rod T=OC Heat Vibrating copper atom Copper rod
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Reversibility Reversibility is the ability to run a process back and forth infinitely without losses. Reversible Process > Example: Perfect Pendulum Irreversible Process >Example: Dropping a ball of clay
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Reversible Process > Examples: > Perfect Pendulum >Mass on a Spring >Dropping a perfectly elastic ball >Perpetual motion machines More?
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Irreversible Processes > Examples: >Dropping a ball of clay A-lammering a nail Applying the brakes to your car >Breaking a glass More?
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Sources of Irreversibilities > Friction (force drops) >Voltage drops Pressure drops > Temperature drops >Concentration drops
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>First Law of Thermodynamics can neither be created nor destroyed
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>Second Law of Thermodynamics >naturally occurring processes are directional >these processes are naturally
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> Third Law of Thermodynamics temperature of absolute zero is not possible
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Heat into Work hot Heat ngine Qhot cold cold
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Carnot Equation: Efficiency > The maximum work that can be done by a heat engine is governed by: Efficiency - wmax = 1- Qhot cold hot
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Work into Heat > A/though there are limits on the amount of heat converted to work, work may be converted to heat with 100% efficiency.
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Heat Capacity for Constant Volume Processes (Cv) Heat is added to a substance of mass m in a fixed volume enclosure, which causes a change in internal energy, U. Thus, The v subscript implies constant volume
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Heat Capacity for Constant Pressure Processes (Cp) Ax AT Heat, Q added Heat is added to a substance of mass m held at a fixed pressure, which causes a change in internal energy, U, AND some PV work.
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Cp Defined Thus, Q = AU + PAV = AH = m cp AT The p subscript implies constant pressure H, enthalpy. is defined as U + PV, so AH = A(U+PV) = AU + VAP + PAV = AU + PAV Experimentally, it is easier to add heat at constant pressure than constant volume, thus you will typically see tables reporting Cp for various materials (Table 21.1 in your text).
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Thank you

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