16.1 Thermal Energy and Matter Chapter 16 Thermal Energy and Heat.

16.1 Thermal Energy and Matter

Chapter 16Thermal Energy and Heat


In what direction does heat flow spontaneously?

Heat is ________________________________ ____________________________________________________________________________

Work and Heat

Heat flows spontaneously from _______objects to ________objects.


What is the temperature of an object related to?

Temperature

Temperature is related to the average kinetic energy of the particles in an object due to their _____________________________________.


Temperature is a _____________________ ____________________________________.

• On the Celsius scale, the reference points are the ________and __________points of water.

• On the Kelvin scale, ________________is defined as a temperature of 0 kelvins.

Temperature


As an object heats up, __________________ ______________________, on average. The average kinetic energy of the particles increases.

• One way that heat flows is by the transfer of energy in _______________.

• On average, ________________ particles lose energy. ________________particles gain energy.

• Overall, collisions transfer thermal energy from _________________________________.

Temperature


What two variables is thermal energy related to?

Thermal energy is the total ____________and ________________energy of all the particles in an object.

Thermal Energy

Thermal energy depends on the __________, ______________, and ______________(solid, liquid, or gas) of an object.


Thermal energy depends on ___________. A cup of tea and a teapot full of tea can have the same temperature.

• The average kinetic energy of the particles is the same in the cup and the pot.

• There is more ___________________in the teapot because it contains more particles.

Thermal Energy


Thermal energy depends on ______________. Compare a cup of hot tea with a cup of cold tea.

• In both cups, the tea has the same mass and number of particles.

• The average kinetic energy of particles is higher in the hot tea, so it has __________thermal energy.

Thermal Energy


Thermal energy depends on mass and temperature.

A. The tea is at a higher temperature than the lemonade.

B. The lemonade has more thermal energy because it has many more particles.

Thermal Energy


What causes thermal expansion?

Thermal expansion _____________________ ____________________________________________________________________________

Thermal Contraction and Expansion

Thermal expansion occurs when particles of matter move farther apart as _____________ increases.


If you take a balloon outside on a cold winter day, it _______________in a process of thermal contraction.

• As temperature ______________, the particles that make up the air inside the balloon move more slowly, on average.

• Slower particles collide less often and exert less force.

• Gas pressure _______________and the balloon ______________________.

Thermal Energy


If you bring the balloon inside, it ________________.

Gases expand ________than liquids and liquids usually expand ___________than solids.

Thermal Energy

As temperature increases, the alcohol in a thermometer _______________, and its height increases in proportion to the increase in temperature.

In an oven thermometer, strips of steel and brass expand at different rates as the coil heats up. The ___________________________________________________________________________________.


How is a change in temperature related to specific heat?

Specific heat is _________________________ ____________________________________________________________________________

Specific Heat

The lower a material’s specific heat, the more its ______________________________ ____________________________________________________________________________


When a car is heated by the sun, the temperature of the metal door increases more than the temperature of the plastic bumper.

The iron in the door has a _____________ _____________than the plastic in the bumper.

Specific Heat


Specific Heat


In this formula, heat is in _________, mass is in __________, specific heat is in ________, and the temperature change is in degrees ___________________.

Specific Heat


1. How much heat is needed to raise the temperature of 100.0 g of water by 85.0°C?

2. How much heat is absorbed by a 750-g iron skillet when its temperature rises from 25°C to 125°C?

Answer: Q = m * c * ∆T

Specific Heat

Answer: Q = m * c * ∆T


3. In setting up an aquarium, the heater transfers 1200 kJ of heat to 75,000 g of water. What is the increase in the water’s temperature? (Hint: Rearrange the specific heat formula to solve for ∆T.)

Answer: ∆T = Q / (m x c)

4. To release a diamond from its setting, a jeweler heats a 10.0-g silver ring by adding 23.5 J of heat. How much does the temperature of the silver increase?

Answer: ∆T = Q / (m x c)

Specific Heat


5. What mass of water will change its temperature by 3.0°C when 525 J of heat is added to it?

Answer: m = Q / (∆T x c)

Specific Heat


On what principle does a calorimeter operate?

A calorimeter is an ______________________ ______________________________________

Specific Heat

The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.


According to the law of conservation of energy, ____________________________________________________________________________________________________________________________________________________

The calorimeter is sealed to prevent thermal energy from escaping.

Specific Heat


A calorimeter is used to measure specific heat. A sample is heated and placed in the calorimeter. _______________________________________________________________

Specific Heat


Assessment Questions

1. What is the thermal energy of an object? a. the total number of atoms or molecules

b. the total kinetic energy of the atoms or molecules

c. the average kinetic energy of the atoms or molecules

d. the average mechanical energy of the atoms or molecules



2. What causes a gas to expand when its temperature is increased?

a. The number of particles increases as temperature increases.

b. Each particle expands as its temperature increases, so the total volume increases.

c. As temperature increases, more electrons leave atoms and move separately.

d. As gas particles move faster, they overcome some forces of attraction.

3. The specific heat of water is 4.18 J/g•°C. How much heat is required to raise the temperature of 1,000 grams of water by 50°C? a. 83.6 Jb. 83.6 kJc. 209 Jd. 209 kJ



4. What property of matter can be measured using a calorimeter? a. temperature

b. thermal expansion

c. specific heat

d. mass

5. Temperature is the transfer of thermal energy from one object to another.

TrueFalse

16.2 Heat and Thermodynamics

Newton’s cradle helps to visualize conduction. One ball strikes the rest, and most of the kinetic energy is transferred to one ball on the end.


Conduction

Why is conduction slower in gases than in liquids or solids?

Conduction is __________________________ ______________________________________

Conduction in gases is slower than in liquids and solids because _______________ ____________________________________________________________________________


Conduction occurs within a material or ___________________________________.

In conduction, collisions between particles transfer thermal energy, without any overall transfer of matter.

Conduction

A thermal conductor _________________ ______________________________________________________________________


The arrows show how thermal energy is conducted away from the heat source in a metal frying pan.

Conduction


____________are good thermal conductors.

When a frying pan is on a hot stove, the bottom of the metal pan heats first and the metal handle last. The flames ____________ ____________________________________

Tile is a better conductor than wood. A tile floor feels colder than a wooden floor when both floors are at room temperature. The tile ____________________________________ ________________________________________________________________________

Conduction


Thermal Insulators

A material that conducts thermal energy poorly is called a _____________________.

Air is a very good insulator. Wool garments and plastic foam cups use trapped air to slow down conduction.

Conduction


Convection

In what natural cycles do convection currents occur?

Convection ____________________________ ____________________________________________________________________________

Convection currents are important in many natural cycles, such as _________________, _________________, and movements of ___ _____________________________________.


A. Passing sandbags along a line is like transferring thermal energy by convection.

B. The arrows show convection of air in an oven.

Convection


A ______________________occurs when a fluid circulates in a loop as it alternately heats up and cools down.

• Air at the bottom of an oven heats up, expands, and becomes less dense. __________________________.

• Rising hot air cools as it moves away from the heat source.

• As a result, the coolest air is at the top of the oven.

Convection


Radiation

How does an object’s temperature affect radiation?

Radiation is ___________________________ ____________________________________________________________________________

All objects radiate energy. As an object’s temperature ____________, the rate at which it radiates energy ___________________.


When you stand to the side of a charcoal grill, heat reaches you ______________________ ____________________________________

The sun warms you by ______________on a clear day. The space between the sun and Earth has no air to transfer thermal energy.

Heat lamps used in restaurants are another example of radiation.

Radiation


The heating coil on a stove radiates thermal energy.

The changing color of the red arrows indicates that the farther you are from the coil, ______________ ____________________.

Radiation


_____________________________________________________________________________________________thermodynamics.

_____________________(1818-1889) carefully measured the energy changes in a system. Joule's system included a falling weight that turned a paddle wheel in a container of water.

Joule found that the work done by the falling weight almost exactly equaled the thermal energy gained by the water.

Thermodynamics


The first law of thermodynamics states that _____________________________________.

Thermodynamics

First Law of Thermodynamics


Energy cannot be created or destroyed, but it can be ______________into different forms.

Added energy increases the thermal energy of a system or does work on the system. In either case, energy is conserved.

Thermodynamics


Pushing on the pump does work on the system.

Some of the work is converted into ___________ ________________, which heats the air in the pump and the tire.

Thermodynamics


The second law of thermodynamics states _____________________________________ _________________________________________________________________________________________________________________.

Thermodynamics

Second Law of Thermodynamics


Thermal energy flows spontaneously only from _____________to ___________________objects.

• A refrigerator must do work to transfer thermal energy from the cold food compartment to the warm room air.

• The thermal energy is released by _____________at the bottom or in the back of the refrigerator.

Thermodynamics


A heat engine is _____________________________ ___________________________________________

• The efficiency of a heat engine is always less than _________________

• Thermal energy that is not converted into work is called __________________________

• Waste heat is lost to the surrounding environment.

Thermodynamics


__________________________will always make a system less orderly, unless work is done on the system.

For example, if you walk long enough, your shoelaces will become untied. But the opposite won't happen; shoelaces don't tie themselves. Disorder in the universe as a whole is always increasing.

Thermodynamics


The third law of thermodynamics states that _____________________________________.

Thermodynamics

Third Law of Thermodynamics


The efficiency of a heat engine increases with a greater difference between ____________________ ____________________________________________________________________________________

A heat engine could be ________________efficient if the cold outside environment were at absolute zero (0 Kelvin). This would violate the third law of thermodynamics.

Thermodynamics


The third law of thermodynamics states that absolute zero cannot be reached.

This physicist uses a laser to cool rubidium atoms to 3 billionths of a Kelvin above absolute zero.

Thermodynamics



1. What form of energy transfer requires the motion of particles of a fluid? a. conduction

b. convection

c. radiation

d. insulation

2. What happens in every case in which energy is added to a system?a. Temperature increases.b. Work is done on the

system.c. All of the energy can be

accounted for as work or heat.

d. An identical amount of energy is removed from the system.



3. Thermal energy can move from a cooler object to a warmer object when a. the warmer object is

larger.b. the cooler object has

more thermal energy.c. energy is transferred by

radiation.d. work is done on the

system.

4. According to the third law of thermodynamics, it is impossible

a. to cool an object to absolute zero.

b. transfer thermal energy from a cooler object to a warmer object.

c. convert energy from one form to another.

d. account for all of the energy in a system.



1. All metals are good thermal insulators.

TrueFalse

16.3 Using Heat

Heat engines played a key role in the development of the modern industrial world. Steam locomotives were an important early use of the steam engine. Electric power plants today use steam turbines.

16.3 Using Heat

What are the two main types of heat engines?

Heat Engines

The two main types of heat engines are the ____________________________and the _____________________________________.

16.3 Using Heat

External Combustion Engine

A steam engine is an external combustion engine—an ______________________________ ________________________________________

• __________________________developed the first practical steam engine in 1712 to pump water out of coal mines.

• __________________________designed an engine in 1765 that operated at a higher temperature and was more efficient.

Heat Engines

16.3 Using Heat

When the valve in a steam engine slides, steam is trapped in the cylinder. The steam expands and cools as it pushes the piston to the left.

Heat Engines

Hot steam inSlide valve

PistonCylinder

Exhaust steam out

Valve rod

Piston rod

16.3 Using Heat

Internal Combustion Engine

An internal combustion engine _____________ ________________________________________________________________________________

Most internal combustion engines use pistons that move up and down inside cylinders. Each upward or downward motion of a piston is called a __________.

Heat Engines

16.3 Using Heat

Most cars have a ________________internal combustion engine. This diagram shows only one of the cylinders during each stroke.

Heat Engines

Intake stroke Compression Stroke Power stroke Exhaust stroke

Cylinder

Piston

Air-fuel mixture

Intake valve

Spark plug

Exhaust valve

Exhaust gases

16.3 Using Heat

In an internal combustion engine, the cooling system and exhaust transfer heat from the engine to the environment.

Gasoline engines are more efficient than old-fashioned steam engines, but they still are not very efficient. About _______________of the energy in a gasoline engine is converted to work.

Heat Engines

16.3 Using Heat

How do most heating systems distribute thermal energy?

Heating Systems

__________________________________________________________________________________________________________________

16.3 Using Heat

A central heating system heats many rooms from _________________________________.

• The most commonly used energy sources for central heating systems are _____________________________ _____________________________________________

• Heating systems differ in how they transfer thermal energy to the rest of the building.

Heating Systems

16.3 Using Heat

Hot-Water Heating• At the boiler, heating oil or natural gas burns and

_________________________________. • The circulating pump carries the hot water to

______________________in each room.• The hot water transfers thermal energy to the

radiator by __________________________.

Heating Systems

16.3 Using Heat

• The hot pipes heat the room air by _____________ and _______________________.

• Hot air rises and sets up a convection current in each room.

• The cooled water returns to the boiler.

Heating Systems

16.3 Using Heat

Within the pipes of this hot-water heating system, the water circulates in a ________________current. In each room, the air moves in a convection current.

Heating Systems

Radiator

Thermostat

Expansion tank

Circulating pump

Boiler

Exhaust vent

16.3 Using Heat

Steam Heating

Steam heating is very similar to hot-water heating except that ______________ is used instead of hot water.

• The transfer of heat from the steam-heated radiator to the room still occurs by _____________________.

• Steam heating often is used in older buildings or when many buildings are heated from one central location.

Heating Systems

16.3 Using Heat

Electric Baseboard Heating

An electric baseboard heater ________________ _______________________________________.

• A conductor is used to convert electrical energy to ___________________________.

• The hot coil heats the air near it by conduction and radiation.

• Convection circulates the warm air to heat the room.

Heating Systems

16.3 Using Heat

Forced-Air Heating

Forced-air heating systems use ______________ _______________________________________________________________________________.

• Convection circulates air in each room. • Warm air entering the room ____________________

__________________________________________. • Cool room air returns to the furnace through floor

vents on the other side of the room.

Heating Systems

16.3 Using Heat

Hot air enters the room through a supply vent in the floor. The hot air rises as cooler, denser air in the room sinks.

Heating Systems

Cool air sinks

Return vent

Duct

Furnace

Hot air rises

Supply vent

Chimney

16.3 Using Heat

How does a heat pump reverse the normal flow of heat?

A heat pump __________________________ _____________________________________.

Cooling Systems

Heat pumps must do work on a refrigerant in order to reverse the normal flow of thermal energy.

16.3 Using Heat

A refrigerant is a ____________________________ __________________________________________

• When the refrigerant absorbs heat, ________________ _____________________________________________

• When the refrigerant gives off heat,_________________ _____________________________________________

Cooling Systems

16.3 Using Heat

Refrigerators

A refrigerator is a heat pump—_______________ _______________________________________________________________________________.

• A ______________must do work to move refrigerant through tubing inside the refrigerator walls.

• Coils of tubing underneath or behind the refrigerator release heat absorbed from the food compartment and thermal energy produced by the work the motor does.

Cooling Systems

16.3 Using Heat

When a refrigerator door is open, some thermal energy from the room enters the refrigerator. _______ ___________________________________________________.

Cooling Systems

Temperature in room: 25°C

Temperature in refrigerator: 3°C

16.3 Using Heat

Air Conditioners• The ________________ in a room air

conditioner raises the temperature and pressure of the refrigerant, turning it into a hot, high-pressure gas.

• The condenser coil is hotter than the outside air, so heat flows spontaneously to the outside air.

• The ________________cools and condenses into a liquid.

Cooling Systems

16.3 Using Heat

• The liquid refrigerant then flows through the expansion valve and ________________________.

• As the cold refrigerant flows through the evaporator coil, it absorbs _________________ from the warm room air.

• The fan sends cold air back into the room. The refrigerant becomes a vapor, and the process starts all over again.

Cooling Systems

16.3 Using Heat

In a window air conditioner, outside air is heated as a fan blows it through the condenser coil.

Cooling Systems

Warm air out

Warm air inEvaporator coil Liquid absorbs heat to become vapor.

Cold air out

Compressor

Expansion valve Pressure drops, causing liquid refrigerant to become cold.

Condenser coilVapor cools to liquid as heat is removed.

16.3 Using Heat


1. Only about one-third of the energy in gasoline is converted to work in an internal combustion engine. The rest of the chemical energy is

a. lost as unused mechanical energy.

b. destroyed by the engine.c. converted to potential

energy.d. discharged as waste

heat.

2. How is a room heated by an electric baseboard heating system?a. conduction and

convection onlyb. conduction and

radiation onlyc. convection and

radiation onlyd. conduction, convection,

and radiation

16.3 Using Heat


3. How do air conditioners reverse the normal flow of heat?

a. moving cool air from outside to inside the houseseparating warm atoms from cool atomsvaporizing and condensing a refrigerantblowing the warm air away with a fan

4. Forced air heating systems are often used to heat many buildings from a central location.

TrueFalse

16.1 Thermal Energy and Matter Chapter 16 Thermal Energy and Heat.

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