Energy

• Energy - the ability to cause change or movement

• Examples:

• energy can change the temperature of a pot of water

• energy can change the direction and speed of a baseball.

• https://www.youtube.com/watch?v=_uLSFigtLKg

Energy—What is energy?

Energy ChangesEnergy Changes

11

Energy

• Word “energy” comes from Greek “energos” which means “active”

• Energy is the ability to cause change– Can cause a physical change (state of matter)– Can allow a chemical reaction to occur

• Change in the arrangement of atoms in a molecule

• energy in a thunderstorm produces lightning and thunder

• energy can change the arrangement of atoms in molecules and cause chemical reactions to occur

Energy—What is energy?Energy ChangesEnergy Changes

11

Examples: continued

• Energy comes in different forms from a variety of sources.

• chemical energy in the form of food energy

Forms of EnergyEnergy ChangesEnergy Changes

11

• nuclear energy contained in the nucleus of the atom to produce electricity

Types of energy• Kinetic and potential (mechanical)

All energy is kinetic or potential but there are different kinds of kinetic and potential energy1. Electrical (movement of electrons)

2. Electromagnetic (light/radiation energy)

3. Chemical (energy in chemical bonds)

4. Thermal (heat)

5. Nuclear (energy stored in atoms)

6. Sound energy

Kinetic energy• The energy an object has due to its motion

• The amount of kinetic energy of an object depends on its speed and mass– What is speed

_____________________________– What is mass

_____________________________

• Higher speed or higher mass = more kinetic energy

• https://www.youtube.com/watch?v=4CWlNoNpXCc

• energy stored in the chemical compounds in your muscles changes to energy of motion

• An energy transformation occurs if energy changes from one form to another.

• Example:

Energy Transformations


11

• a car sits in sunlight all day, the energy in sunlight (radiant energy) changes to heat energy that warms the inside of the car

• energy used to stretch and move a rubber band changes into heat energy that raises the temperature of the rubber band

Energy Transformations: continuedEnergy ChangesEnergy Changes

11

• During energy transformations:

• the total amount of energy stays the same

• energy is never lost or gained—it only changes form

Using Energy Transformations


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• An electric current in a wire has electrical energy that can be used in many ways.

Example:

A light bulb converts electrical energy into heat and light energy when you flip on a switch.

• a moving ball due to its motion

Kinetic Energy (KE)


11

• kinetic (kih NE tihk) energy (KE) - the energy an object has due to its motion

• a football thrown by a quarterback

• a sky diver or a leaf falling toward Earth

Examples of kinetic energy (KE):

• moving objects have kinetic energy (KE)• not all moving objects have the same amount of

kinetic energy

Mass, Speed, and Kinetic Energy (KE)Energy ChangesEnergy Changes

11

• amount of kinetic energy (KE) an object has depends on the massmass & speedspeed of the object

• Example:• Mass: a small rock and a large boulder rolling down

a hill at the same speed• the large boulder could cause more damage – the

large boulder has more kinetic energy • larger the mass of the object the more kinetic

energy (KE)

Mass, Speed, and Kinetic Energy (KE)


11

Example:Speed: The faster a bowling ball moves, the more

pins it can knock down - the more kinetic energy (KE) it has

• kinetic energy (KE) increases as speed increases

• https://www.youtube.com/watch?v=-dpBVtAbKJU

• Kinetic energy (KE) can be transferred from one object to another when they collide.

Transferring Kinetic Energy (KE)


11

• Example• Even if the bowling ball does not touch all of the

pins, it still can knock them all down with one roll.

• The bowling ball transfers kinetic energy (KE) to a few pins.

• These pins transfer the kinetic energy (KE) to the remaining pins and knock them down.

• The skier has no kinetic energy (KE) when she is standing at the top of the hill.

Potential Energy (PE)


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• But as she skis down and moves faster, her kinetic energy (KE) increases. • Gravity pulls the skier down the hill.

• When the skier’s position is at the top of the hill, she has a form of energy called potential energy (PE).

Potential energy• Energy stored due to an objects location

• Potential energy (PE) - energy that is stored because of an object’s position

• http://phet.colorado.edu/sims/energy-skate-park/energy-skate-park_en.jar



11

Potential energy

• The potential energy depends on the location of the object and its mass



11

• By using the ski lift to take her to the top of the hill, the skier increased her potential energy (PE) by changing her position.

• When you raise an object above its original position, it has the potential to fall.

Increasing Potential Energy (PE)


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• If it does fall, it has kinetic energy (KE).

• To raise an object, you have to transfer energy to the object.

• This energy becomes stored as potential energy (PE).

Increasing Potential Energy (PE)


11

• If the object were lifted higher, the potential energy (PE) would increase.

• The higher an object is lifted above Earth, the greater its potential energy (PE).

• Kinetic energy (KE) also can be transformed into potential energy (PE).

Converting Potential (PE) and Kinetic Energy (KE)


11

Example:

• Suppose you throw a ball straight up into the air.

• The muscles in your body cause the ball to move upward when it leaves your hand - an energy transfer

• the moving ball has kinetic energy (KE)

• As the ball gets higher and higher, its potential energy is increasing.

Converting Potential and Kinetic Energy


11

• At the same time, the ball is slowing down and its kinetic energy (KE) is decreasing.



11

• At its highest point, the ball comes to a stop for an instant before it starts to fall downwardagain. Here all the kinetic energy (KE) the ball had when it left your hand has been converted to potential energy (PE).

• As the ball falls downward, its potential energy (PE) is converted back into kinetic energy (KE).



11

• If you catch the ball at the same height abovethe ground as when you threw it upward, its kinetic energy will be the same as when it left your hand.

• Just like a ball falling to the ground, the potential energy (PE) that water has at the top of a waterfall is transformed into kinetic energy as it falls downward.

Energy Changes in Falling Water


11

• The kinetic energy (KE) of falling water can be used to generate electricity.

Energy Changes in Falling Water


11

• Water backs up behind a dam on a river, forming a lake or reservoir. (PE)

• The water near the top of the dam then falls downward. (KE)

• The kinetic energy (KE) of the moving water spins generators, which produce electricity.

• The potential energy (PE) of the water behind the dam is transformed into electrical energy.

Conserving energy

• James Joule demonstrated the law of conservation of energy in 1840– Law states energy can not be created or

destroyed, just transferred from one form to another

– The total amount of energy in the universe stays the same

– Energy is measured in “Jules of work”

• Example:

• Kinetic energy (KE) - converts into heat energy when two objects rub against each other

Conservation of Energy


11

• A book slides across a table - it will slow down and eventually stop

• The book’s kinetic energy (KE) isn’t lost. • Its kinetic energy (KE) converted into heat

energy as the book rubs against the surface of the table.

Energy transformation

• Energy transformation- when energy changes from one form to another form– The total amount of energy stays the same,

but the type of energy changes

• Chemical energy in a battery is changed into kinetic energy

Energy transfer

• When you raise an object, you use kinetic energy which is transferred into potential energy (because it has the potential to fall)

Other energy transfers• A waterfall has potential energy at the top

of the waterfall and kinetic as it falls

• Can convert the kinetic energy into electrical energy or use the kinetic

energy to move other

things

• Chemical energy in a soccer player’s leg muscles is converted into kinetic energy (KE) when she swings her leg.

Following the Energy Trail


11

• When the ball is kicked - kinetic energy (KE) is transferred to the ball

• After the ball rolls for a while, it comes to a stop.

• As the ball rolled, its kinetic energy (KE) was transformed into heat energy as the ball rubbed against the grass.

http://www.youtube.com/watch?v=_uLSFigtLKg

What is Electrical Energy?

o Energy caused by the movement of

electrons

o Easily transported through power lines and then converted into other forms of

energy

What is Chemical Energy?

o Energy that can be released during chemical

reactions. oEnergy stored in chemical

bonds.

What is Thermal Energy?• The microscopic kinetic energy

of atoms and molecules• A measure of how active the

atoms and molecules are. • A hot object has excited

molecules and atoms that move fast

• A cooler object has slower moving molecules and atoms

Measuring Temperature• Temperature - related to the kinetic energy (KE)

of all the atoms or molecules in an object (average kinetic energy)

TemperatureTemperature

22

• A practical way to measure temperature is to use a thermometer

• Because atoms or molecules are so small andobjects contain so many of them - it is impossible to measure the kinetic energy of each individual atom or molecule

The Fahrenheit Scale• Fahrenheit scale –

• the freezing point of water = 32°F• the boiling point of water = 212°F


22

• The space between is divided into 180 equal degrees

• used mainly in the United States

The Celsius Scale• Celsius (SEL see us) temperature scale


22

• the freezing point of water = 0°C

• the boiling point of water = 100°C

• The space between is divided into 100 equal degrees

• used more widely throughout the world

Temperature = heat• Temperature and heat are not the same

thing– Temperature: measure of how hot something

is– Heat: flow of energy from a hotter object to a

cooler one

• Measuring temperature and heat– Temperature units: degrees Fahrenheit,

Celsius, Kelvin– Heat units: Joule, calorie, BTU, kilocalorie

Heat

• Heat: transfer of energy from one object to another due to a difference in temperature

• Heat flows from warmer object to cooler one

• Heat transfer doesn’t mean high temperature (ex heating beaker of ice)

HOTHEAT

COLD More

HEAT

COLD

VERY HOT

Heat transfer

• Heat flows from hotter objects to colder objects.

• Heat flow depends on the temperature difference between objects

• Heat is not temperature

• There are thermal insulators and conductors

More about heat…

• Thermal Conductors– Materials through which it is easy to transfer

thermal energy– Metals are the best thermal conductors

• Thermal insulators– Poor conductors of heat– Air is a good insulator, therefore, many

insulating materials have air spaces– Other good insulators are wood, rubber, and

ceramic

Heat on the Move• A transfer of energy occurs if there is a

temperature difference between two areas in contact.


22

• Heat is always transferred from warm places to cooler ones.

• Heat transfers can take place in three ways

• conduction

• convection

• radiation

Heat on the Move


22

• Conduction transfers heat mainly through solids and liquids

• Convection transfers heat mainly through liquids and gases

• Radiation can transfer energy through space and air

Conduction• Conduction (kun DUK shun) - the transfer of

energy by collisions between the atoms in a material. • A spoon in boiling water becomes warmer

because its atoms and molecules moved faster


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• faster particles then collided with slower-moving particles in the colder of the spoon

• Kinetic energy (KE) is transferred up the spoon’s handle.

Bumping Along• In a solid, the particles involved don’t travel

from one place to another.


22

• Conduction usually occurs in solids.

• They simply move back and forth in place, bumping into their neighbors transferringenergy from faster-moving particles to slower-moving ones.

Conductors• thermal conductors - materials through which it

is easy to transfer energy


22

• Most metals are good conductors of heat. • Metals such as gold, silver,

and copper are the best thermal conductors.

• Copper is widely available and less expensive than gold or silver.

Insulators• Materials made of plastics also are often good

insulators.


22

• If you put a plastic spoon in boiling water, it takes a long time for it to get hot.

• Many cooking pans have plastic handles that remain at a comfortable temperature while the pans are used for cooking.

Insulators• thermal insulators - materials that are poor

conductors of heat


22

• Clothes and blankets -

• poor conductors of heat• heat cannot escape easily from your body by

trapping your body heat around you

• help keep you warm because they are made of materials that contain many air spaces.

• Air is a good insulator.

Convection• Convection (kun VEK shun) transfers heat

when particles move between areas that differ in temperature.


22

• most common in gases and liquids• As temperature increases, particles move around

more quickly, and the distance between particles increases.

• This causes density to decrease as temperature increases.

• Cooler, denser material forces the warmer, less dense material to move upward.

Examples of Convection• Sometimes a bird can stay in the air without

flapping its wings because it is held up by a thermal.


22

• A thermal• column of warm air that is

forced up as cold air around it sinks

• a convection current in the air

Convection• Some homes are heated by convection.


22

Examples of Convection

• Convection also occurs in liquids.


22

• In a pot of boiling water, the warmer, less dense water is forced up as the cooler, denser water sinks.

• Convection currents on a larger scale are formed in oceans by cold water flowing from the poles and warm water flowing from tropical regions.

Radiation• radiation (ray dee AY shun) - the transfer of

energy by waves


22

• radiation waves can be visible light waves or types of waves that you cannot see

• When radiation waves strike an object - their energy can be absorbed and the object’s temperature rises

• Radiation waves can travel through air and even through a vacuum

Radiation Examples:

• The Sun transfers energy to Earth through radiation.


22

• Heat is transferred by radiation from the fire and you become warmer. You also can use radiation to cook food.

• A microwave oven cooks food by using microwave radiation to transfer energy to the food.

Convection, conduction, radiation

• Thermal energy passes by conduction, convection, or radiation

• Conduction – transfer of heat by direct contact to a solid substance.

Example: the transfer of thermal energy from the metal bar to your hand.

• Radiation – transfers energy by waves through empty space. Can be visible light or other types of radiation (fex microwave, UV radiation).

Heat

• Convection – transfer of heat energy between a solid surface and the nearby liquid or gas in motion

• May create a convection

cell

Convection cell

• Heat rises, cool air sinks– Why?

• What is density?

Expansion, contraction

• Expansion: as an object is heated up, the atoms are excited and move more quickly. As they move more quickly, they move farther and expand. – If your balloon deflates, heat it up

• Contraction: as an object cools, the atoms move more slowly and become closer together. They contract, or take up a smaller space.– Which will be more dense? A heated balloon or

cooled one?

Examples

• Which is conduction, convection, radiation?

A

C

B

More on types of energy

• Nonrenewable energy – Made from nonrenewable sources (sources

that don’t renew themselves as fast as they are consumed)

• Nuclear, fossil fuels, natural gas• These are created naturally but take millions of

years to form and we use them much more quickly than they form.

More on energy

• Renewable energy– Made from renewable sources (can be

replenished naturally at same rate or faster than they are consumed)

• Solar, wind, tidal, wave, hydroelectric, geothermal, bio-fuel

• Some renewable sources are not as good as others…

– Discuss downside of biofuel

• http://www.youtube.com/watch?v=_uLSFigtLKg

• http://www.youtube.com/watch?v=qybUFnY7Y8w

11Section CheckSection Check

Question 1

What is energy?

Energy is the ability to cause change. An object that has energy can do something or make something happen.

Answer


Question 2

A book resting on top of a bookshelf has no kinetic energy. It does, however, have _______ energy.

A. chemical B. mechanicalC. negativeD. potential


AnswerThe answer is D. If the book falls, its potential energy will be replaced by kinetic energy.


Question 3

As the mass of a moving object increases, its kinetic energy _______.

A. decreasesB. increasesC. stays constantD. terminates


Answer

The answer is B.


Question 1

The two most common temperature scales are the _______ and the _______ scale.

A. absolute and KelvinB. Fahrenheit and KelvinC. Fahrenheit and CelsiusD. Kelvin and Celsius


Answer

The answer is C. In science you will also encounter the Kelvin scale but it is not commonly used in everyday temperature readings.


Question 2

Explain how temperature is related to the motion of molecules in a material.

Answer

Temperature is a measure of the average value of the kinetic energy of the molecules in a substance.

Section CheckSection Check

12-212-2Question 3

How are temperature and pressure related?


12-212-2 AnswerWhen air is heated, its molecules move faster and the air expandsThis makes the air less dense and it rises. As this less dense air rises and exerts less pressure on anything below it.Cooled air becomes denser and sinks as the molecules slow down and move closer together.This cool air exerts more pressure on anything below it.


Question 4Heat can move from place to place in different ways. When heat moves from one object to another as a result of direct contact, the process is known as _______.

A. conductionB. convectionC. radiationD. thermal transfer


Answer

The answer is A. An everyday example of conduction occurs when you pick up a cup of coffee and feel the warmth in your fingers.

Chemical Reactions and Energy— What is a chemical reaction?

• In a chemical reaction-

• compounds - broken down

• new compounds - formed

Chemical EnergyChemical Energy

33

Energy in Reactions

• After the hydrogen and oxygen atoms are bound together to form a water molecule, it is difficult to split them apart.


33

• Energy—usually supplied by electricity, heat, or light—is required to break the chemical bonds.

Energy-Absorbing Reactions

• Some chemical reactions need a constant supply of energy to keep them going. These reactions absorb energy. A chemical reaction that absorbs heat energy is called an endothermic (en duh THUR mihk) reaction.


33

• Examples:

• preparation of food

• photosynthesis

Energy-Absorbing Reactions (endothermic chemical reaction)

• Chemical reactions occur when sunlight strikes the leaves of green plants.

• These chemical reactions convert the energy in sunlight into chemical energy contained in a type of sugar. Oxygen also is produced by these chemical reactions.


33

• When the plant is deprived of sunlight, the reactions stop.

Energy-Absorbing Reactions• This process is

called photosynthesis.


33

Energy-Releasing Reactions

• Endothermic chemical reactions are usually important because of the compounds the reactions produce.


33

• Other reactions are important because they release energy.

• Exothermic (ek soh THUR mihk) reactions are chemical reactions that release heat energy.

Energy-Releasing Reactions• When a substance burns, atoms in the

substance combine with oxygen atoms in the air.


33

• An exothermic reaction occurs & energy in the form of heat and light is released.

• The exothermic reaction that occurs when a material burns by combining with oxygen is called combustion.

Rate of Reaction

• Chemical reactions can occur at different rates.


33

Examples:

• fireworks explode - very fast chemical reaction rate

• rust - very slow chemical reaction rate

Changing the Rate of Reaction• Two ways to change the rate of a chemical

reaction are:• changing the temperature• adding a type of compound called a catalyst


33

• A catalyst (KA tuh list) - a substance that changes the rate of a chemical reaction without any permanent change to its own structure.

• enzymes – protein catalysts that control many cell processes in your body

Changing the Rate of Reaction

• Enzymes are found throughout your body and are important for growth, respiration, & digestion.


33

Changing the Rate of Reaction


33

• When you chew a piece of bread, glands in your mouth produce saliva that contains an enzyme (amylase).

• The enzyme in saliva acts as a catalyst to help break down starches in food into smaller molecules.


33

A substance that speeds up a chemical reaction is known as a _______

Question 1


33

A catalyst can be added to speed up a chemical reaction. A catalyst changes the rate of a chemical reaction without any permanent change to its own structure.

Answer


33

What occurs when a chemical compound is broken apart?

Question 2


33

When a chemical compound is broken apart, the bonds between the atoms that make up the compound are broken.

Answer


33

Where is the energy stored in a compound?

Question 3

Energy is stored in the bonds between the atoms. In order to release that energy the bonds must be broken.

Answer

• Energy is the ability to cause change.

Energy Changes

• Energy can have different forms. Energy can be transformed from one form into another.

11Reviewing Main IdeasReviewing Main Ideas

• Kinetic energy is the energy an object has due to its motion. Kinetic energy increases as the speed of an object increases.

• Potential energy is stored energy that increases as an object’s height increases.

• Temperature is a measure of the average kinetic energy of the particles in a material.

Temperature

• The movement of energy from a warmer object to a cooler one is called heat.


• Heat can be transferred by conduction, convection, and radiation.

• The energy stored in chemical bonds is chemical energy.

Chemical Energy

• Chemical reactions can release or absorb energy. Exothermic reactions are chemical reactions that release energy. Endothermic reactions absorb energy.


• Changing the temperature and adding catalysts can change the rate of chemical reactions.

Question 1

Chapter ReviewChapter Review

Why does convection usually occur in liquids and gases, but not in solids?

Answer


In liquids and gases, atoms and molecules are free to move from place to place. As a result, they can transfer energy by moving from a warmer place to a cooler place in a material. In solids, atoms and molecules don’t move from place to place within the solid.

Question 2


In an exothermic reaction, heat energy is _______.

A. absorbedB. createdC. destroyedD. released

Answer


The answer is D. Exothermic reactions release heat energy.

Question 3


How does the Sun’s energy reach Earth?

AnswerThe Sun’s energy reached Earth by radiation. The other forms of heat transfer can’t occur through empty space.

Question 4


One of the reasons the handle of a pan is made of wood rather than metal is that wood does not transfer heat as quickly from the hot pan to your hand. In other words, wood is a poor _______.

A. conductorB. coolantC. insulatorD. thermometer

Answer


The answer is A. Wood is a poor conductor of heat energy.

Question 5


Chemical energy is a form of which type of energy?

A. kinetic energyB. nuclear energyC. heat energyD. potential energy

Answer


The answer is D. Chemical energy is a form of potential energy that is stored in the binds between atoms in a compound.

Standardized Test PracticeStandardized Test Practice

Question 1

Burning is a(n) _______ chemical reaction.

A. endothermicB. exothermicC. photosynthesisD. kinetic


Answer

The answer is B. Because heat is released, the chemical reaction is exothermic.


Question 2

The temperature of a material increases when the atoms in the material _____.

A. move closer togetherB. move farther apartC. move fasterD. move slower


Answer

The answer is C. When temperature increases, the atoms are moving faster and have more kinetic energy.


Question 3

As the height of a ball increases, its _____ energy increases.

A. kineticB. electricalC. heatD. potential


Answer

The answer is D. When the height of an object increases, its potential energy increases.


Question 4

As water falls from the top of a waterfall, which forms of energy are changing?

A. electrical and chemicalB. kinetic and potentialC. kinetic and electricalD. potential and nuclear


Answer

The correct answer is A. Kinetic energy is the energy of motion.


Question 5

What determines the kinetic energy of an object?

A. only its massB. only its speedC. both its mass and speedD. both its mass and speed as well as its direction


Answer

The answer is C. Mass and speed are the two factors you need to know to determine the kinetic energy of an object.


Question 1

What is energy?

Energy is the ability to cause change. An object that has energy can do something or make something happen.

Answer


Question 2

A book resting on top of a bookshelf has no kinetic energy. It does, however, have _______ energy.

A. chemical B. mechanicalC. negativeD. potential


AnswerThe answer is D. If the book falls, its potential energy will be replaced by kinetic energy.


Question 3

As the mass of a moving object increases, its kinetic energy _______.

A. decreasesB. increasesC. stays constantD. terminates


Answer

The answer is B.


Question 1

The two most common temperature scales are the _______ and the _______ scale.

A. absolute and KelvinB. Fahrenheit and KelvinC. Fahrenheit and CelsiusD. Kelvin and Celsius


Answer

The answer is C. In science you will also encounter the Kelvin scale but it is not commonly used in everyday temperature readings.


Question 2

Explain how temperature is related to the motion of molecules in a material.

Answer

Temperature is a measure of the average value of the kinetic energy of the molecules in a substance.


12-212-2Question 3

How are temperature and pressure related?


12-212-2 AnswerWhen air is heated, its molecules move faster and the air expandsThis makes the air less dense and it rises. As this less dense air rises and exerts less pressure on anything below it.Cooled air becomes denser and sinks as the molecules slow down and move closer together.This cool air exerts more pressure on anything below it.


Question 4Heat can move from place to place in different ways. When heat moves from one object to another as a result of direct contact, the process is known as _______.

A. conductionB. convectionC. radiationD. thermal transfer


Answer

The answer is A. An everyday example of conduction occurs when you pick up a cup of coffee and feel the warmth in your fingers.


33

A substance that speeds up a chemical reaction is known as a _______

Question 1


33

A catalyst can be added to speed up a chemical reaction. A catalyst changes the rate of a chemical reaction without any permanent change to its own structure.

Answer


33

What occurs when a chemical compound is broken apart?

Question 2


33

When a chemical compound is broken apart, the bonds between the atoms that make up the compound are broken.

Answer


33

Where is the energy stored in a compound?

Question 3

Energy is stored in the bonds between the atoms. In order to release that energy the bonds must be broken.

Answer

End of Chapter Summary File

More on types of energy

• Nonrenewable energy – Made from nonrenewable sources (sources

that don’t renew themselves as fast as they are consumed)

• Nuclear, fossil fuels, natural gas• These are created naturally but take millions of

years to form and we use them much more quickly than they form.

Documents

Energy