be ready to take notes!. unit 6 lesson 11 thermal energy lesson 12 temperature lesson 13 (optional)

Be ready to take notes!

Unit 6• Lesson 11 Thermal Energy• Lesson 12 Temperature• Lesson 13 (Optional)

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Agenda • House keeping• Thermal Energy

– Conduction– Convection– Radiation

• Temperature – Temperature vs. Thermal energy– Expansion and Contraction– Thermometers

• Fahrenheit, Celsius, Kelvin• Converting

• Exit ticket

House keeping

• Office Hours– Mrs. Schneider’s Tuesday 2-3pm– Mrs. Burt’s Wednesday 2-3pm

• You can attend either office hours, but only Kmail your teacher with questions.

• Remember to be positive!

Lesson 11 ObjectivesThermal Energy 1. Compare and contrast the transfer of thermal

energy through radiation, convection, or conduction.

2. Recognize that changes in the temperature of an object will affect the kinetic energy of that object.

3. Describe how thermal energy flows from a system of higher temperature to a system of lower temperature.

Why does an popsicle melt on a warm tongue?

• There is a temperature difference between the tongue and the popsicle, so heat energy flows from the warm tongue into the cold popsicle.

• This means that the popsicle melts as it gets warmer.

Review

• Kinetic energy is the energy of motion• Potential energy is the stored energy of position.

New• Thermal energy is the total energy of an object. That is the total of the kinetic and potential energy

Thermal Energy depends on the size of the object.

A BWhich block has more atoms?Which block has more energy?Which block has more thermal energy?

AllA

Thermal energy depends on temperature of the object.

A B

Which block has more kinetic Energy?Which block’s atoms are moving faster?Which block as more thermal energy?

Thermal energy is the total of all the internal energy in an object.

Heat

The flow of thermal energy from one object

to another.

Heat always flows from

warmer to cooler objects. Ice gets

warmer while hand gets

cooler

Cup gets cooler while hand gets

warmer

Heat transfer is a flow of energy between two objects due to a temperature difference

between the objects.

–Heat transfer is the way in which thermal energy is moved from a hot object to a colder object.

Hot water Cold water

(90. oC) (10. oC)

Water Water

(50. oC) (50. oC)

What is thermal equilibrium?

• Thermal equilibrium – when the atoms of both blocks are moving the same amount or have the same temperature.

Thermal Equilibrium

Thermal Equilibrium When hot water and ice

are placed in a closed system:

1. The energy lost by the hot water is equal to

2. The energy gained by the ice.

3. Eventually, the contents reach thermal equilibrium.

What is Heat?

• Heat is the movement of thermal energy, or the transfer of thermal energy, from one substance to another;

• Why does a chocolate bar melt when you hold it in your hand?

Why does a chocolate bar melt when you hold it in your hand?

• Heat is transferred from warmer to cooler objects

• Remember: Objects do not contain heat. Instead they contain thermal energy. Heat is just the transfer of that thermal energy.

Heat is the transition of thermal energy from a hotter to a cooler body

• Radiation• Conduction• Convection

Heat is transferred in three ways

What is conduction?How are the particles arranged in a solid, a liquid and a gas?

solid liquid gasParticles that are very close together can transfer heat energy as they vibrate. This type of heat transfer is called conduction.

CONDUCTION . . . . . . . . . . . . . . . heat transferred through a substance or from one substance to another by direct contact of molecules.

CONDUCTION can take place in solids, gases, and liquids, but takes place BEST in solids, because the molecules of a solid are in direct contact with one another.

Which picture is showing conduction?

A B

C

Convection• Convection is the

transfer of heat by the actual motion of a fluid (liquid or gas) in the form of currents.

• Convection comes from a Latin word meaning "to carry together."

CONVECTION . . . . . . . . . .

. . . . . . . . . heat energy transferred through liquids and gases by means of up-and-down movements called convection currents.

WHEN A LIQUID is heated, the molecules begin to move faster.

The hot water at the bottom of the pot rises to the top of the pot, and is replaced by the cooler water. Next the cooler water is heated.

Boiling water

Weather patterns and their movement are dependent on convection currents . . . . .

Does your refrigerator use convection?

YES!

RADIATION heat energy transferred through space.

Heat from the sun reaches the Earth by means of RADIATION . . . . . . ( 8 minutes at 186,000 miles per second).

fireplace . . . Heat lamp . . .

Land heats up and cools down faster than water

Lesson 12 Objectives

Temperature 1. Explain that changes in the position and motion of

atoms in a solid, liquid, or gas are the result of temperature increase or decrease.

2. Explain how the kinetic energy of atoms or molecules of different objects varies with their temperature.

3. Describe the differences between thermal energy, kinetic energy, potential energy, and temperature.

Temperature

Temperature is a measure of average kinetic energy of the molecules of an object.

As temperature increases, so does the average kinetic energy of the molecules.

ExamplesWhy does this help to get the

lid off?

The temperature of the metal

increase, it expands.

LIQUIDS . . . . . . .

Most liquids expand when they are heated.

Exception: water expands as it cools. As the volume increases, the density decreases.

Temperature• The higher the average KE, the higher the temperature• Which substance has a lower temperature?

When the temperature increases the particles move faster.

Temperature and Thermal EnergyWhat’s the difference?

• Temperature IS NOT HOW HOT OR COLD SOMETHING IS!

• Temperature is defined as the measure of the average kinetic energy of the individual particles in an object.

• Thermal energy is defined as the total energy of all the particles in an object.

Thermal Energy VS. Temperature

THERMAL ENERGY=POTENTIAL + KINETIC ENERGY

TEMPERATURE=AVERAGE KINETIC ENERGY

TEMPERATURE IS a measure of the average kinetic energy of the molecules in a substance.

Thermal energy is defined as the total energy of all the particles in a substance

Adding thermal energy to a substance increases the average kinetic energy of the molecules and therefore causes a rise in temperature.

Higher temperature = faster molecular motionLower temperature = slower molecular motion

If these two blocks are the same temperature that would mean what?

They have the same average kinetic energy of their atoms.

A THERMOMETER IS AN instrument used for measuring temperature and works because of thermal expansion . . . . . . .

As the liquid (usually alcohol) in a thermometer gets warmer, it expands and rises in the tube. The opposite happens as the liquid gets cooler.

Fahrenheit and Celsius

• People around the world measure temperature with different scales.

• Two common scales are Fahrenheit and Celsius.

• Let’s compare them by considering the freezing and boiling points of water.

CELSIUS FAHRENHEIT boiling 100 degrees point 212 degrees

(water)

human 37 degrees body 98.6 degrees

temp

Comfortable room temp.

freezing 0 degrees point 32 degrees

(water)

20 degrees 68 degrees

Converting Fahrenheit and Celsius

• To convert Fahrenheit to Celsius: °C = (5/9) (°F – 32)• To convert Celsius to Fahrenheit: °F = (9/5) (°C) + 32

• Notice the difference! Order matters!• Change 20°C to Fahrenheit• °F = (9/5) (20°C) + 32• °F = (1.8) (20°C) + 32• °F = (36) + 32• °F = 68• 20°C = 68°F

SCIENTISTS SOMETIMES USE another metric temperature scale the KELVIN SCALE.

You can CONVERT Celsius degrees to Kelvins (K) simply by ADDING 273 to the Celsius temperature.

0 ºC = 273 K 100 ºC = 373 K 0 K = -273 ºC

The LOWEST temperature than can be reached ( a point in which all molecular motion stops ), is called ABSOLUTE ZERO or 0 K.

AB

CD

Celsius (C) 0

0212

Matching…

1. Farenheit Scale2. Celsius Scale3. Kelvin Scale4. Absolute Zero5. Thermal Energy6. Temperature

a. the temperature scale used in most of the world

b. The total energy of all particles in a substance

c. The temperature at which no more energy can be removed from an object

d. A temperature scale in which the interval between the freezing point and boiling point of water is divided into 180 equal parts

e. A measure of average kinetic energy of the individual particles in an object

f. A temperature scale with no negative numbers

Matching…

1. Farenheit Scale2. Celsius Scale3. Kelvin Scale4. Absolute Zero5. Thermal Energy6. Temperature

a. the temperature scale used in most of the world

b. The total energy of all particles in a substance

c. The temperature at which no more energy can be removed from an object

d. A temperature scale in which the interval between the freezing point and boiling point of water is divided into 180 equal parts

e. A measure of average kinetic energy of the individual particles in an object

f. A temperature scale with no negative numbers

Exit ticket

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