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An introduction to thermodynamics
Heat and temperature An introduction to thermodynamics
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Kinetic molecular theory
Collective hypotheses about the particulate nature of matter and the surrounding space Greeks - earliest written ideas on ________ Current view Matter comprised of _____________________ particles - atoms Atoms combine to form __________________ Many macroscopic phenomena can be traced to interactions on this level atoms invisible molecules
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Molecules Chemical elements - defined by each unique type of ______________ Compounds - pure substances made up of _______ or more atoms chemically ____________ Molecules Smallest unit retaining the properties of a compound “molecules” can stand for either atoms (monatomic molecules) or polyatomic molecules atoms two combined
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Phases of matter - solids
shape Definite _________ and ___________ Rigid ____ structure Atoms/molecules bonded in place Allowed motions restricted to _____________ in place only volume 3-D vibration
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Phases of matter - liquids
Definite ____________ volume, indefinite ___________ Only ____________ cohesive bonds between component molecules Constituent molecules mostly in contact ____________ motions Vibration ______________ Limited translation or sliding shape weak Allowed Rotation
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Phases of matter - gases
shape Indefinite ___________________ volume and __________ Molecules mostly not in contact Allowed motions Vibration and rotation (molecules with more than one atom) Translation on ____________, mostly ________ paths random free
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Molecular motions kinetic average
Characterized by average _____________ energy in a large sample Temperature Measure of __________ kinetic energy on the molecules making up a substance Proportional to average KE Evidence Gases diffuse _________ at higher temperatures ____________/contraction with increasing/ ____________ temperature kinetic average faster Expansion decreasing
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Temperature A measure of the _____________ energy of an object
Thermometers Used to measure __________________ Rely on thermometric properties Example: bimetallic strips and thermostats internal temperature
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Temperature scales Defined various reference points ________________
Celsius Conversion formulas Fahrenheit to Celsius Celsius to Fahrenheit Celsius to Kelvin Fahrenheit Kelvin
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Heat transfer A form of energy _________________ between two objects
External energy - total potential and kinetic energy of an every-day sized object Internal energy - total kinetic energy of the molecules in that object External can be transferred to internal, resulting in a __________ ________________. transfer temperature increase
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Heat versus temperature
A measure of hotness or ______________ of an object Based on average molecular kinetic energy Thermal Energy Based on _____________ internal energy of molecules ______________ amount at same temperature doubles thermal energy coldness total Doubling
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Heat Heating methods Definition
Temperature ____________: Energy always moves from ___________ temperature regions to ______________ temperature regions Energy-form conversion: Transfer of heat by doing _____ Definition A measure of the internal energy that has been _______________ or ______________ from another object Two related processes “Heating” = __________ internal energy “Cooling” = ___________ internal energy difference added higher removed lower increases removes work
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Measures of heat Metric units English system Mechanical ______________
______________ (cal) - energy needed to raise temperature of 1 g of water 1 degree ______ kilocalorie (kcal, Calorie, Cal) - energy needed to raise temperature of 1 ___ of water 1 degree Celsius English system British thermal unit (________) - energy needed to raise the temperature of 1 lb of water 1 degree _________________ Mechanical ______________ 4.184 J = 1 _________ calorie btu Celsius Fahrenheit Equivalence kg calorie
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Specific heat Variables involved in heating Temperature change Mass
Type of material Different materials require different amounts of __________ to produce the same _______________ change Measure = specific heat Summarized in one equation energy temperature
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Heat flow Three mechanisms for heat transfer due to a temperature difference ____________________ Convection Natural flow is _____________ from higher temperature regions to cooler ones Conduction Radiation ALWAYS
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Conduction flowing Heat ____________ _____________ matter Mechanism
Hotter atoms ____________ with cooler ones, transferring some of their ______________ ___________ physical contact required; cannot occur in a vacuum Poor conductors = insulators (___________, __________, air…) through collide energy Direct Styrofoam wool
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Sample conductivities
Material Relative conductivity Silver 0.97 Iron 0.11 Water 1.3x10-3 Styrofoam 1.0x10-4 Air 6.0x10-5 Vacuum
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Convection Energy transfer through the __________ motion of ___________ material Examples Space heater Gas furnace (_________ _____________) Natural convection mechanism - “hot air ______________” bulk heated forced convection rises
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Radiation Radiant energy - energy associated with electromagnetic waves Can operate through a _______________ All objects ____________ and _____________ radiation Temperature determines Emission ____________ _____________________ of emitted light Type of radiation given off Temperature determined by balance between rates of emission and absorption Example: Global warming vacuum absorb emit rate Intensity
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Energy, heat, and molecular theory
Two responses of matter to heat ________________ ____________ within a given phase Heat goes mostly into internal kinetic energy ______________ heat _______________ ______________ at constant temperature Related to changes in internal potential energy ___________ heat Temperature change Specific Phase (State) change Latent
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Phase changes Solid/liquid Liquid/gas Solid/gas Latent heat Fusion
Vaporization Sublimation Temperature (Direction ->) Melting point Boiling point (Direction <-) Freezing point Condensation point
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Evaporation and condensation
any Individual molecules can change phase ______ ______ Evaporation: Energy required to overcome phase __________________ Higher energy molecules _______________ the surface can then escape Condensation: Gas molecules near the surface _________ KE to liquid molecules and ____________ time Cohesion (attraction to other particles) close to lose condense
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Thermodynamics The study of heat and its relationship to _______________ and other forms of energy Thermodynamic analysis includes System Surroundings (everything else) Internal energy (the total internal potential and _____________ energy of the object in question) mechanical kinetic
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Thermal Equilibrium When two substances at _______________ temperatures are placed in contact, heat energy will flow from the substance with the _____________ temperature to the substance with the ______________ temperature. This transfer will continue until the objects reach the same _________ _____________ This is called thermal equilibrium different higher lower final temperature
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Thermal Equilibrium The amount of __________ lost by the ___________ temperature object is equal to the __________ gained by the __________ temperature object The change in the _______________ of the two objects is the same, but one loses that amount of ___________ and the other gains that amount of ______________ energy higher energy lower thermal energy energy energy
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Thermal Equilibrium The change in the __________________ of the two objects is not necessarily the same, however. Consider the following example: Suppose you poured a glass of 10º C water into a 30º C swimming pool. Would the final temperature of the water be 20º C, less than 20º C, or more than 20º C? Why? temperature
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Thermal Equilibrium Suppose a hot piece of metal (700º C) were dropped into a large tub of 30º C water. What would we need to know to determine the final temperature that they would reach? ___________________________________ How big is the tub of water? (Mass) How big is the piece of metal? (Mass) The specific heat of the metal The specific heat of water
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Thermal Conductivity The rate at which a substance transfers thermal energy is known as thermal conductivity. ________________ are substances that have high conductivities. An example of this would be __________. ________________ are substances that have low conductivities. Some examples of this would be ______________________. Conductors metals Insulators glass, plastic, or rubber
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Radiation of Thermal Energy
The rate at which a substance radiates thermal energy depends on several factors: ________________________ Color of the object Temperature Surface area Texture of the surface
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Radiation of Thermal Energy
The ___________ the surface area of an object is, the faster it will radiate thermal energy. Therefore, a rough object will radiate energy ______________ than a smooth object. Objects that are black will radiate thermal energy ______________ than white objects. Objects with a _____________ temperature will radiate energy faster than objects with a ______________ temperature. greater faster faster greater lower
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Radiation of Thermal Energy
Objects both emit and absorb thermal radiation continually If an object is radiating more energy than it is absorbing, ________________________ If an object is absorbing more energy than it is radiating, _________________________ it will decrease its temperature it will increase its temperature
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Radiation and Thermal Equilibrium
An object in thermal equilibrium is radiating thermal energy __________________ it is absorbing it. Therefore, there is no _________________ ___________________________________. at the same rate that change in the temperature of the object
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