16.1 -2.3 Standard Engineering Specification for Thermal Insulation Design
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Transcript of Chapter 16 Thermal Energy and Heat. 16.1 Thermal Energy and MatterThermal Energy and Heat 16.1...
Chapter 16Chapter 16
Thermal Energy Thermal Energy and Heatand Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
16.1 Thermal Energy and 16.1 Thermal Energy and MatterMatter
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Work and HeatWork and Heat
Heat is the transfer of thermal Heat is the transfer of thermal energy from one object to another energy from one object to another because of a difference in because of a difference in temperature. temperature.
Heat flows spontaneously from hot Heat flows spontaneously from hot objects to cold objects. objects to cold objects.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
TemperatureTemperature
Temperature is a measure of how Temperature is a measure of how hot or how cold an object is hot or how cold an object is compared to a reference point. compared to a reference point.
Temperature is related to the Temperature is related to the average kinetic energy of the average kinetic energy of the particles in an object due to their particles in an object due to their random motions through space. random motions through space.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
As an object heats up, its particles As an object heats up, its particles move faster, on average. move faster, on average.
As a result, the average KE of the As a result, the average KE of the particles and the temperature particles and the temperature increase. increase.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Why does heat flow from high to low Why does heat flow from high to low temperature? temperature?
Heat flow is by the transfer of energy Heat flow is by the transfer of energy in collisions. in collisions.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
High-energy particles lose energy, High-energy particles lose energy, and low-energy particles gain energy and low-energy particles gain energy during collisions. during collisions.
The collisions transfer thermal The collisions transfer thermal energy from hot to cold objects. energy from hot to cold objects.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Thermal EnergyThermal Energy
Thermal energy is the total potential Thermal energy is the total potential and kinetic energy of all the particles and kinetic energy of all the particles in an object. in an object.
Thermal energy depends on mass, Thermal energy depends on mass, temperature, and phase of an object. temperature, and phase of an object.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Figure 2 shows the particles in a cup Figure 2 shows the particles in a cup of hot tea and in a pitcher of of hot tea and in a pitcher of lemonade. lemonade.
The tea is at a higher temperature, The tea is at a higher temperature, but the pitcher of lemonade has but the pitcher of lemonade has many more particles. many more particles.
The pitcher of lemonade actually has The pitcher of lemonade actually has more thermal energy.more thermal energy.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Thermal Contraction and Thermal Contraction and ExpansionExpansion
Thermal expansion is an increase in Thermal expansion is an increase in the volume of a material due to a the volume of a material due to a increase in temperature. increase in temperature.
Thermal expansion occurs when Thermal expansion occurs when particles of matter move farther apart particles of matter move farther apart as temperature increases. as temperature increases.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Gases expand more than liquids and Gases expand more than liquids and liquids usually expand more than liquids usually expand more than solids. solids.
A gas expands more easily because A gas expands more easily because the forces of attraction in a gas are the forces of attraction in a gas are weaker.weaker.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Specific HeatSpecific Heat
Specific heat is the amount of heat Specific heat is the amount of heat needed to raise the temperature of one needed to raise the temperature of one gram of a material by one degree gram of a material by one degree Celsius. Celsius.
The lower a material’s specific heat, the The lower a material’s specific heat, the more its temperature rises when a given more its temperature rises when a given amount of energy is absorbed by a given amount of energy is absorbed by a given mass. mass.
Specific heat is measured in joules per Specific heat is measured in joules per gram per degree Celsius (J/ggram per degree Celsius (J/gooC). C).
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
The heat (Q) absorbed by a material The heat (Q) absorbed by a material equals the product of the mass, the equals the product of the mass, the specific heat, and the change in specific heat, and the change in temperature. temperature.
Q=mc∆tQ=mc∆t
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Specific HeatSpecific Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Specific HeatSpecific Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Specific HeatSpecific Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Specific HeatSpecific Heat
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Q=mc∆tQ=mc∆t
m=Q/c∆tm=Q/c∆t
c=Q/m∆tc=Q/m∆t
∆∆t=Q/mct=Q/mc
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
Measuring Heat ChangesMeasuring Heat Changes
A calorimeter is an instrument used A calorimeter is an instrument used to measure changes in thermal to measure changes in thermal energy. energy.
A calorimeter uses the principle that A calorimeter uses the principle that heat flows from hotter object to a heat flows from hotter object to a colder object until both reach the colder object until both reach the same temperature. same temperature.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
According to the law of conservation According to the law of conservation of energy, the thermal energy of energy, the thermal energy released by a test sample is equal to released by a test sample is equal to the thermal energy absorbed by its the thermal energy absorbed by its surroundings. surroundings.
Figure 4 shows how a calorimeter Figure 4 shows how a calorimeter can be used to measure specific can be used to measure specific heat.heat.
16.1 Thermal Energy and Matter16.1 Thermal Energy and Matter Thermal Energy and HeatThermal Energy and Heat
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
16.2 Heat and 16.2 Heat and ThermodynamicsThermodynamics
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
ConductionConduction Conduction is the transfer of thermal Conduction is the transfer of thermal
energy with no overall transfer of energy with no overall transfer of matter. matter.
Conduction occurs within a material Conduction occurs within a material or between materials that are or between materials that are touching. touching.
In conduction, collisions between In conduction, collisions between particles transfer thermal energy. particles transfer thermal energy.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Conduction in gases is slower than in Conduction in gases is slower than in liquids and solids because the liquids and solids because the particles in a gas collide less often. particles in a gas collide less often.
In metals, conduction is faster In metals, conduction is faster because the electrons are free to because the electrons are free to move about. move about.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Thermal ConductorsThermal Conductors
A thermal conductor is a material A thermal conductor is a material that conducts thermal energy well. that conducts thermal energy well.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Thermal InsulatorsThermal Insulators
A material that conducts thermal A material that conducts thermal energy poorly is called a thermal energy poorly is called a thermal insulator. insulator.
Air is a very good insulator.Air is a very good insulator.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
ConvectionConvection
Convection is the transfer of thermal Convection is the transfer of thermal energy when particles in a fluid move energy when particles in a fluid move from one place to another. from one place to another.
A convection current occurs when a A convection current occurs when a fluid circulates in a loop as it fluid circulates in a loop as it alternately heats up and cools down. alternately heats up and cools down.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
RadiationRadiation
Radiation is the transfer of energy by Radiation is the transfer of energy by waves moving through space. waves moving through space.
All objects radiate energy. All objects radiate energy. As an object’s temperature As an object’s temperature
increases, the rate at which it increases, the rate at which it radiates energy increases.radiates energy increases.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
ThermodynamicsThermodynamics
The study of conversions between The study of conversions between thermal energy and other forms of thermal energy and other forms of energy is called thermodynamics. energy is called thermodynamics.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Joule carefully measured the energy Joule carefully measured the energy changes in a system which included changes in a system which included a falling weight that turned a paddle a falling weight that turned a paddle wheel in a container of water. wheel in a container of water.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
As the weight fell, the paddle As the weight fell, the paddle churned a known mass of water. churned a known mass of water.
The water heated up due to friction The water heated up due to friction from the paddle. from the paddle.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Joule found the work done by the Joule found the work done by the falling weight almost exactly equaled falling weight almost exactly equaled the thermal energy gained by the the thermal energy gained by the water. water.
The law of conservation applied to The law of conservation applied to work, heat, and thermal energy.work, heat, and thermal energy.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
First Law of First Law of ThermodynamicsThermodynamics
The first law of thermodynamics The first law of thermodynamics states that energy is conserved. states that energy is conserved.
If energy is added to a system, it can If energy is added to a system, it can either increase the thermal energy of either increase the thermal energy of the system or do work on the the system or do work on the system. system.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Second Law of Second Law of ThermodynamicsThermodynamics
The second law of thermodynamics The second law of thermodynamics states that thermal energy can flow states that thermal energy can flow from colder objects to hotter objects from colder objects to hotter objects only if work is done on the system. only if work is done on the system.
A heat engine is any device that A heat engine is any device that converts heat into work. converts heat into work.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
One consequence of the second law One consequence of the second law is that the efficiency of a heat engine is that the efficiency of a heat engine is always less than 100%.is always less than 100%.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
The best an engine can do is to The best an engine can do is to convert most of the input energy into convert most of the input energy into useful work. useful work.
Thermal energy that is not converted Thermal energy that is not converted into work is called waste heat. into work is called waste heat.
A heat engine can do work only if A heat engine can do work only if some waste heat flows to a colder some waste heat flows to a colder environment outside the engine. environment outside the engine.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Spontaneous changes will always Spontaneous changes will always make a system less orderly, unless make a system less orderly, unless work is done on the system. work is done on the system.
Disorder in the universe is always Disorder in the universe is always increasing. increasing.
16.2 Heat and Thermodynamics16.2 Heat and Thermodynamics Thermal Energy and HeatThermal Energy and Heat
Third Law of Third Law of ThermodynamicsThermodynamics
The third law of thermodynamics The third law of thermodynamics states that absolute zero cannot be states that absolute zero cannot be reached. reached.
