table of contents chapter: heat and states of matter section 2: states of matterstates of matter...

Table of ContentsTable of Contents

Chapter: Heat and States of Matter

Section 2: States of Matter

Section 1: Temperature and Thermal Energy

Section 3: Transferring Thermal EnergySection 4: Using Thermal Energy

11

• The motion of the particles in matter is described by kinetic theory of matter.

• Matter is composed of particles that are atoms, molecules, or ions that always are in random motion.

Kinetic Theory of Matter

Temperature and Thermal EnergyTemperature and Thermal Energy

• The temperature of a substance is a measure of the average kinetic energy of its particles.

11

• The SI unit for temperature is the Kelvin (K).

Temperature

Temperature and Thermal EnergyTemperature and Thermal Energy

11 Temperature

Temperature and Thermal EnergyTemperature and Thermal Energy

• Commonly used temperature scales are the Celsius scale and the Fahrenheit scale.

11

• The sum of the kinetic and potential energies of all the particles in an object is the thermal energy of the object.

• The increase in an object’s speed doesn’t affect the random motion of its particles, so it doesn’t affect its thermal energy.

Thermal Energy

Temperature and Thermal EnergyTemperature and Thermal Energy

11

• Heat is thermal energy that flows from something at a higher temperature to something at a lower temperature.

• Heat is a form of energy, so it is measured in joules.

Heat

Temperature and Thermal EnergyTemperature and Thermal Energy

11

• The amount of thermal energy needed to raise the temperature of 1 kg of some material by 1°C is called the specific heat of the material.

• Specific heat is measured in joules per kilogram per degree Celsius.

Specific Heat

Temperature and Thermal EnergyTemperature and Thermal Energy

11 Changes in Thermal Energy

Temperature and Thermal EnergyTemperature and Thermal Energy

11

• The specific heat of a material can be measured using a device called a calorimeter.

• In a calorimeter, a heated sample transfers thermal energy to a known mass of water.

Measuring Specific Heat

Temperature and Thermal EnergyTemperature and Thermal Energy

11 Measuring Specific Heat

Temperature and Thermal EnergyTemperature and Thermal Energy

• The thermal energy released by the sample is equal to the thermal energy absorbed by the water.

11Section CheckSection Check

Question 1

How is temperature related to kinetic energy?

FL: SC.B.1.4.3

11Section CheckSection Check

Temperature is a measure of the average kinetic energy of the particles in an object or material. As the temperature increases, the average speed of the particles increases.

Answer

FL: SC.B.1.4.3

11Section CheckSection Check

Question 2

How does thermal energy differ from kinetic energy?

Answer

Thermal energy is the sum of the kinetic and potential energy of all the particles in an object.

FL: SC.B.1.4.3

11Section CheckSection Check

Question 3

The amount of heat that is needed to raise the temperature of 1 kg of a material by 1º C is called the __________ of the material.

A. densityB. massC. specific heatD. thermal energy

11Section CheckSection Check

Answer

The answer is C. Specific heat is measured in joules/kilogram °C.

22States of MatterStates of Matter

• The particles of a solid are packed closely together and are constantly vibrating in place.

Four States of Matter

• The attractions between particles are strong and solids have a fixed volume and shape.

Solid State

22States of MatterStates of Matter

• The attractive forces are strong enough to cause particles to cling together.

Liquid State

• Liquids have a definite volume, but not a definite shape.

22States of MatterStates of Matter

• In a gas the forces between particles are so weak that the particles no longer cling together.

Gas State

• Gases do not have a definite shape or volume.

22States of MatterStates of Matter

• The most common state of matter in the universe is the plasma state.

Plasma State

• Plasma is matter consisting of positively and negatively charged particles and does not have a definite shape or volume.

22States of MatterStates of Matter

• The temperature at which a solid begins to melt is its melting point.

Changing States

• The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the heat of fusion.

Melting

22States of MatterStates of Matter

• The heat of fusion is also the energy released when a liquid freezes.

Freezing

• The attractive forces are strong enough that the particles form an ordered arrangement.

22States of MatterStates of Matter

• Vaporization occurs as liquid changes into a gas.

Vaporization

• Vaporization that occurs at the surface of a liquid is called evaporation.

• Evaporation causes the temperature of the liquid to decrease.

22States of MatterStates of Matter

• The boiling point of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface.

Boiling

• The heat of vaporization is the amount of energy required for 1 kg of the liquid at its boiling point to become a gas.

22States of MatterStates of Matter

• The heat of vaporization is also the amount of energy released during condensation.

Condensation

• This graph shows the temperature change of water as thermal energy is added.

22States of MatterStates of Matter

• The average kinetic energy of the water molecules doesn’t change.

Condensation

• The temperature remains constant during melting.

22States of MatterStates of Matter

Condensation

of the gas increases as energy is added.

• After the liquid water has changed completely into a gas, the temperature

22States of MatterStates of Matter

• The increased separation between the particles results in the expansion of the object and the size of the object increases.

Thermal Expansion

• When a material cools, the particles in the material move more slowly and become closer together.

The Thermal Expansion of Matter

22States of MatterStates of Matter

• The forces between the particles in liquids are weaker than the forces between the particles in a solid.

Thermal Expansion of Liquids

• The same temperature increase usually causes liquids to expand much more than solids.

22States of MatterStates of Matter

• In a gas, the forces between particles are much weaker than they are in liquids.

Thermal Expansion of Gases

• Gases expand even more than liquids for the same increase in temperature.

22Section CheckSection Check

Question 1

_________ is a state of matter consisting of positively and negatively charged particles that exists where the temperature is extremely high.

FL: SC.A.1.4.3

A. GasB. LiquidC. PlasmaD. Solid

22Section CheckSection Check

Answer

The answer is C. Plasma is found in the Sun, stars, lightning bolts and neon lights.

FL: SC.A.1.4.3

22Section CheckSection Check

Question 2

Most __________ materials have a specific type of geometric arrangement.

FL: SC.A.1.4.3

A. gaseousB. inertC. liquidD. solid

22Section CheckSection Check

The answer is D. The particles in most solids align themselves in ordered geometric patterns.

Answer

FL: SC.A.1.4.3

22Section CheckSection Check

Question 3

The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the _______.

A. heat of energyB. heat of fusionC. heat of meltingD. heat of vaporization

22Section CheckSection Check

Answer

The correct answer is B. Heat of fusion causes an ice cube to become liquid water.

33Ways to Transfer Thermal Energy

• This transfer of thermal energy between colliding particles is conduction.

Transferring Thermal EnergyTransferring Thermal Energy

• Kinetic energy is transferred when these faster-moving atoms collide with slower-moving particles.

Conduction

33Thermal Conductors

• The rate at which thermal energy is transferred depends on the material.

Transferring Thermal EnergyTransferring Thermal Energy

• A material in which thermal energy is transferred easily is called a thermal conductor.

• Gases are poorer thermal conductors than solids or liquids.

33Convection

• Convection is the transfer of thermal energy in a fluid by the movement of fluid from place to place.

Transferring Thermal EnergyTransferring Thermal Energy

• A fluid expands as its temperature increases.

• The density of the fluid therefore decreases.

33Convection

• The warmer water is less dense and is forced upward by the sinking cooler water.

Transferring Thermal EnergyTransferring Thermal Energy

• The warm water transfers thermal energy to the cooler water around it.

33Convection

Transferring Thermal EnergyTransferring Thermal Energy

• When the warm water cools, it becomes denser than the surrounding water and sinks.

• The rising and sinking water forms a convection current.

33Radiation

• Radiation is the transfer of energy by electromagnetic waves.

Transferring Thermal EnergyTransferring Thermal Energy

• Radiation can pass through solids, liquids, and gases, but the transfer of energy by radiation is most important in gases.

33Radiation

Transferring Thermal EnergyTransferring Thermal Energy

• When radiation strikes a material, some energy is absorbed, some is reflected, and some may be transmitted through the material.

33Thermal Insulators

Transferring Thermal EnergyTransferring Thermal Energy

• A material in which thermal energy moves slowly is a thermal insulator.

• Materials that are good conductors of thermal energy, such as metals are poor thermal insulator.

33Section CheckSection Check

Question 1

Describe the difference between conduction and convection.

33Section CheckSection Check

Conduction transfers thermal energy without transferring matter. In convection, the more energetic particles move from one place to another.

Answer

Convection currents result when heated fluid rises and cooler fluid sinks.

33Section CheckSection Check

Question 2

__________ is the transfer of energy by electromagnetic waves.

Answer

The transfer of energy by electromagnetic waves is radiation. Radiation is how Earth gets heat from the Sun.

33Section CheckSection Check

Question 3

Which of the following is the least effective insulator?

FL: SC.A.1.4.2

A. airB. fiberglassC. metalD. wood

33Section CheckSection Check

Answer

The answer is C. Metals are good conductors of heat. And heat flows more rapidly in them.

FL: SC.A.1.4.2

44How is thermal energy used?

• Fuel is burned in a furnace and heats a volume of air.

• A fan blows the heated air through a series of large pipes called ducts.

Using Thermal EnergyUsing Thermal Energy

Heating Systems

Forced-Air Systems

• The ducts lead to openings called vents in each room.

44Radiator Systems

• A radiator is a closed metal container that contains hot water or steam.

• The thermal energy contained in the hot water or steam is transferred to the air surrounding the radiator by conduction.

Using Thermal EnergyUsing Thermal Energy

44Electric Heating Systems

• In an electric heating system, electrically heated coils placed in floors and in walls heat the surrounding air by conduction and convection.

Using Thermal EnergyUsing Thermal Energy

44Thermodynamics

• A system is anything you can draw a boundary around.

Using Thermal EnergyUsing Thermal Energy

Heating and Work Increase Thermal Energy

• The energy transferred to a system is the amount of energy flowing into the system across the boundary.

• The work done on a system is the work done by something outside the system’s boundary.

44The First Law of Thermodynamics

• According to the first law of thermodynamics, the increase in thermal energy of a system equals the work done on the system plus the thermal energy transferred to the system.

Using Thermal EnergyUsing Thermal Energy

• The increase in energy of a system equals the energy added to the system.

44Closed and Open Systems

• A system is an open system if thermal energy flows across the boundary or if work is done across the boundary.

Using Thermal EnergyUsing Thermal Energy

• If no thermal energy flows across the boundary and no outside work is done, the system is a closed system.

44The Second Law of Thermodynamics

• The second law of thermodynamics states it is impossible for thermal energy to flow from a cool object to a warmer object unless work is done.

Using Thermal EnergyUsing Thermal Energy

44Converting Thermal Energy to Work

• No device or process can convert thermal energy completely into work.

Using Thermal EnergyUsing Thermal Energy

44Heat Engines

• A device that converts thermal energy into work is called a heat engine.

Using Thermal EnergyUsing Thermal Energy

• When thermal energy is converted into work, some thermal energy always is transferred to the surroundings.

44Internal Combustion Engines

• The heat engine in a car is an internal combustion engine.

Using Thermal EnergyUsing Thermal Energy

• Each cylinder contains a piston that moves up and down.

• Each up or down movement of the piston is called a stroke.

44Internal Combustion Engines

Using Thermal EnergyUsing Thermal Energy

44Moving Thermal Energy

• Liquid coolant is pumped through an expansion valve and changes into a gas.

Using Thermal EnergyUsing Thermal Energy

• The cold gas is pumped through pipes inside the refrigerator.

• The coolant absorbs thermal energy and the inside of the refrigerator cools.

44Entropy

• According to the laws of thermodynamics, work can be converted completely into thermal energy, but thermal energy cannot be converted completely into work.

Using Thermal EnergyUsing Thermal Energy

• Entropy is a measure of how spread out, or dispersed, energy is.

• Entropy increases when energy becomes more spread out and less concentrated.

44Entropy Always Increases

• According to the entropy principle, all events that occur cause the entropy of the universe to increase.

Using Thermal EnergyUsing Thermal Energy

• The energy that becomes spread out is no longer useable.

44Section CheckSection Check

Question 1

The study of the relationship among thermal energy, heat and work is __________.

FL: SC.B.1.4.6

A. electrical engineeringB. graphical analysisC. specific heatD. thermodynamics

44Section CheckSection Check

Answer

The answer is D, thermodynamics.

FL: SC.B.1.4.6

44Section CheckSection Check

Question 2

According to __________, the increase in thermal energy of a system equals the work done on the system plus the heat transferred to the system.

FL: SC.B.1.4.6

A. Newton’s First LawB. Newton’s Second LawC. the first law of thermodynamicsD. the second law of thermodynamics

44Section CheckSection Check

The answer is C. Doing work on a system is a way of adding energy to a system.

Answer

FL: SC.B.1.4.6

44Section CheckSection Check

Question 3

How does a refrigerator work?

Answer

The refrigerator coolant absorbs thermal energy from inside the refrigerator and releases it into the surrounding air.

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