KWL – Chapter 14
What do we already know?
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What are the three common temperature scales?
o ____________________________
o ____________________________
o ____________________________
 Cold means ________ ________temperatures.
 Hot means ________________ temperatures.
What do we want to learn?
 How does temperature differ from thermal energy?
 How is heat related to thermal energy?
 What are the three forms of heat transfer?
 How is specific heat related to thermal energy?
 What causes matter to change state?
 Why does matter expand when it is heated?
 How is thermal energy related to heat engines and refrigerators?
What have we learned?
Temperature
 Scientists consider the ______________________ that make up matter.
 Matter is made up of tiny particles called atoms and _____________________.
 These particles are always in _____________________
 The energy of motion is called ___________________ energy.
 All particles of matter have _________________ energy.
 The faster particles move the ____________ kinetic energy they have.
 Temperature is a measure of the ___________________________________ of the individual particles in an
object
Measuring Temperature
Three common scales for measuring temperature
o Fahrenheit
o _______________________
o Kelvin
1. Fahrenheit Scale
o Most common temperature scale in the ___________________________________
o The number ________ is assigned to the temperature at which water freezes.
o The number ________ is assigned to the temperature at which water boils.
o The interval between is divided into ________________ equal intervals called degrees Fahrenheit (°F).
2. Celsius Scale
o The temperature scale used in _____________________________
o The number ________ is assigned to the temperature at which water freezes.
o The number ________is assigned to the temperature at which water boils.
o The interval between freezing and boiling is divided into ______ equal parts, called degrees Celsius (°C).
3. Kelvin Scale
o The temperature scale commonly used in ______________________
o The number ________ is assigned to the temperature at which water freezes.
o The number ________ is assigned to the temperature at which water boils
o Units on the Kelvin scale are the same size as those on the Celsius scale
Units are called _____________________ (K).
o Any temperature on the Kelvin scale can be changed to Celsius by subtracting _________
o −273°C is the ____________________ temperature possible - called ___________________________
o At absolute zero, no more energy can be ________________________ from matter.
Thermal Energy
 Thermal energy is the ___________________ energy of all of the particles in a substance.
 Another term is ___________________________ energy.
 Even if two samples of matter are at the same temperature, they __________________ necessarily have the
same total energy.
 The more particles a substance has at a given temperature, the more thermal energy it has.
 Example: 2 liters of hot chocolate at 75°C has more thermal energy than 0.15 liter at 75°C
o
Temperature and Thermal Energy
 Temperature is a measure of the average kinetic energy of the individual particles of matter.
 Thermal energy is the total energy of all of the particles.
 Thermal energy does not depend on just temperature and the number of particles in a substance. It also depends
on how the particles are arranged.
The Nature of Heat
 _________________________is the movement of thermal energy from a substance at a higher temperature to
another at a lower temperature.
 Heat is thermal energy moving from a _____________________object to a cooler object.
 Remember that work also involves the _________________________of mechanical energy.
 Work and heat are both energy transfers, and they are both measured with the same unit -joules.
Heat Transfer
 There are ______________ ways that heat can move.
 Heat is transferred by ___________________________, convection, and radiation.
 Conduction
o
In the process of conduction, heat is transferred from one particle of matter to another
without the ___________________________ of matter itself.
 Example: snap on jeans hot out of the dryer
 Convection
o In convection, heat is transferred by the ________________________of currents within a fluid (a liquid or
gas).
 Example - pot of hot water on a stove
 Water at the bottom of the pot is heated, the particles move faster, and farther apart.
 The heated water becomes less dense so it rises and the surrounding cooler water flows
into its place
 This flow creates a circular motion known as convection current.
 Convection currents transfer air heated by the sun throughout Earth's atmosphere.
 They produce the global winds that form Earth's weather.
 Radiation
o Radiation is the transfer of energy by electromagnetic waves.
 Example: a bonfire or a heat lamp
o Radiation _____________________ require matter to transfer thermal energy.
o The sun's energy that reaches Earth travels through millions of kilometers of empty space.
Movement of Heat
o If two substances have different temperatures, heat will flow from the warmer object to the colder one.
o When heat flows into a substance, the thermal energy and temperature increases.
o Heat will flow from one substance to the other until both have the same temperature.
 Example: homemade ice cream - the ingredients grow colder as thermal energy flows from them
to the ice.
 Heat transfer occurs in only one direction.
Conductors and Insulators
 A material that conducts heat well is called a _______________________________.
o Metals such as silver and stainless steel are _________________ conductors.
o A good conductor, such as a tile floor, will feel cool to the touch because it transfers heat away from your
skin easily.
 A material that does not conduct heat well is called an ___________________________.
o Wood, wool, straw, paper, and cork are good insulators.
o Gases, such as air, are also good insulators.
 Example: rug on a tile floor - Slows the transfer of heat from your skin - so it feels warmer
Specific Heat
 The amount of energy required to raise the temperature of 1 kilogram of a substance by 1 Kelvin
 SI Unit: joules per kilogram-kelvin (J/(kg•K)
 Materials with a high specific heat can absorb a great deal of thermal energy without a great change in
temperature.
 Different materials need more or less heat to change their temperature by the same amount.
o It depends on the chemical makeup of the material.
o Example: Water and Brass
 One kg of water requires 4,180 joules of energy to raise its temperature 1 K
 1 Kg of brass requires 376 J of energy to raise its temperature 1 K
 The energy gained or lost by an object is related to the ________________, change in temperature, and specific
heat of the material.
o Formula:
 Change in energy = Mass x Specific Heat x Change in Temperature
Thermal Energy and States of Matter
 All matter exists in three states
o Solid
 Examples - ice cube, coin, book
 Particles are packed together in relatively ___________________positions
 Particles cannot move out of their positions
 They can only vibrate back and forth
 Retain a fixed shape and volume.
o Liquid
 Examples - water, orange juice, molten steel
 Particles are close together, but not held together as tightly as those of a solid
 Don't have a definite shape
 Do have a definite volume.
o Gas
 Particles move so fast that they don't even stay close together
 Expand to fill all the space available.
Do not have a ____________________ or volume.
 Chemical composition remains the same
 Arrangement of the particles ___________________ from one state to another
 The physical change from one state of matter to another is called a change of state.
o Matter will change from one state to another if thermal energy is ____________________ or released
 During a change of state, the addition or loss of thermal energy changes the arrangement of the particles.
o The average kinetic energy of those particles ____________________ change.
o Temperature is a measure of average kinetic energy - does not change as a substance changes state
 Vaporization
o Process by which matter changes from the liquid to the gas state
o Particles in a liquid absorb thermal energy
o Particles move faster
o Escape the liquid, as gas particles
o If at the surface of a liquid – evaporation
o At higher temperatures - below the surface of a liquid - boiling
 The temperature at which a liquid boils is called its _____________________________
 Condensation
o When a gas loses a sufficient amount of thermal energy, it will change into a liquid.
o A change from the gas state to the liquid state is called condensation.
o Examples
 Beads of water outside of a cold drinking glass - water vapor loses thermal energy
 Melting
o The temperature at which a solid changes to a liquid is called the melting point.
 Freezing
o The temperature at which a substance changes from a liquid to a solid is called its freezing point.
o When a substance loses thermal energy
Thermal Expansion
 As the thermal energy of a substance increases, its particles spread out and the substance expands.
o The expanding of matter when it is heated is known as __________________________ expansion.
o Examples – thermometers, teeth, and thermostats
 Thermal expansion is used in thermostats, or heat-regulating devices.
 Many thermostats contain bimetallic strips - Strips of two different metals joined together
 One expands more to move a switch
 Conversion of thermal energy to mechanical energy requires a device called a ________________ engine.
 Heat engines usually make use of combustion.
o Combustion is the process of burning a _____________________, such as coal or gasoline.
o During combustion, chemical energy that is stored in fuel is converted to thermal energy.
 Heat engines convert thermal energy to mechanical energy.
 Heat engines are classified according to whether combustion takes place outside the engine or inside the engine.
o Fuel is burned _______________________ the engine.
o Example: a steam engine
 Internal combustion engine
o Fuel is burned in cylinders _________________________ the engine
o Example: Diesel and gasoline engines in automobiles
 Refrigerator
o Uses an _________________ energy source to transfer thermal energy from a cool area to a warm area.
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Key Concepts
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Temperature is a measure of the average kinetic energy of each particle within an object.
Three temperature scales are Fahrenheit, Celsius, and Kelvin.
Thermal energy is the total energy of the particles that make up an object.
Heat is a transfer of thermal energy from an object at a higher temperature to an object at a lower
temperature.
Heat is transferred by conduction, convection, and radiation.
A conductor transfers heat well, whereas an insulator does not.
The amount of heat necessary to raise a unit of mass of a substance by a specific unit of temperature is
called the specific heat.
Matter can undergo a change of state when thermal energy is added or removed.
In general, matter expands when it is heated and contracts when it is cooled.
A heat engine converts thermal energy to mechanical energy that can do work.
A refrigerator transfers thermal energy from a cool region to a warm region.
Key Terms
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Fahrenheit scale - the temperature scale on which 32 and 212 are the temperatures at which water
freezes and boils
Celsius scale - the temperature scale on which zero and 100 are the temperatures at which water
freezes and boils
Kelvin scale - the temperature scale on which zero is the temperature at which no more energy can be
removed from matter
absolute zero - the temperature at which no more energy can be removed from matter
heat - the movement of thermal energy from one substance to another
conduction - the transfer of thermal energy between particles within a substance. The transfer of
electrons from a charged object to another object
convection - a current caused by the rising of heated fluid and sinking of cooled fluid.
convection current - a current caused by the rising of heated fluid and sinking of cooled fluid
radiation - the transfer of energy by electromagnetic waves
insulator - a material that does not easily transfer thermal energy or electric current between its particles
specific heat - the amount of thermal energy required to raise the temperature of one kilogram of a
substance by one Kelvin
states - the three forms (solid, liquid, and gas) in which matter exists
change of state - the physical change of matter from one state to another
freezing point - the temperature at which a substance changes from a liquid to a solid
thermal expansion - the expansion of matter when it is heated
thermostat - a device that regulates temperature
bimetallic strip - a strip made of two different metals that expand at different rates
heat engine - a device that converts thermal energy into mechanical energy
external combustion engine - an engine powered by fuel burned outside the engine
internal combustion engine - an engine that burns fuel inside cylinders within the engine