Heat TransferConduction

Investigation 4, Part 2

ESSENTIAL ESSENTIAL QUESTIONSQUESTIONS

* I can explain how radiant energy from the Sun heats solid and liquid materials.

* I can describe how heat transfers through multiple materials.

• I can describe how the atmosphere heated.

• I can determine how to conduct a fair experiment.

In Your Notebook…

• Answer the following questions:

1.What is radiant energy?

2. How does radiation affect the surface of Earth?

In Your Notebook…

• Answer the following questions:

1.What is radiant energy?

Energy that passes through space

2. How does radiation affect the surface of Earth?

Earth receives energy from the Sun

Is the main kind of energy from the Sun that heats the Earth

• Energy is transferred when light energy is absorbed by molecules in Earth’s surface, causing them to move faster,

which increases the temperature!

Heat Transfer• Walking barefoot on a

hot day - – What did you feel?

– Why?

– How did heat transfer from the cement to your feet?

Energy Transfer Challenge

• Heat cold water to about 30˚C without mixing the hot and cold water.

Using these materials:Cold waterHot “Salt” waterCupVialThermometer

How would you set up the experiment?

Hot Water Setup Material Person:• Get a vial, cup, and 2

thermometers • Fill the vial with cold water• Fill the cup half full with hot

salt water• Measure and record temp of

BOTH water samples• Now, warm the cold water to

30 ◦ C without mixing it

with the red (salt) water

The Results

How did heat transfer from the hot to cold water?

Were you able to raise the temperature of the cold water to 30˚C?

The Explanation• No cold, only

heat

• Cold is actually low levels of heat

Heat energy goes out of your hand into the ice cube

Heat

• Motion of atoms and molecules

• Greater motion = more heat energy

• Energy transfer happens between molecules or atoms when they come in contact

Faster moving molecules in the hand bump into the slower moving molecules in the ice

Molecules in hand slow down and we feel it as cold

Multimedia

• Watch the animation of solids, liquids, and gases.

• Watch the animation on conduction.

Heat Transfer Diagram/ Ticket Out the Door

• How could you show the energy transfers as a flow chart from the hot water to the alcohol in the thermometer?

Hot water

Plastic of vial

Cold Water

Glass of thermometer

Alcohol

BREAKPOINT

On Monday, we will explore conduction through materials

Heat Conduction Responses

• Complete the “Heat Conduction” worksheet on page 17 of your lab book.

• BREAKPOINT

Review

• Remember: when two materials at different temperatures make contact, energy transfers from the hotter material to the colder material.

• As materials gain heat energy, the motion of their atoms and molecules increases.

• Molecular Motion = Heat

Multimedia

• Show thermometer animation.

• Draw the energy transfer going on in the animation.

Pot of Soup

• Metal spoon that was in a pot of cooking soup?

• Surprised to find that it was really hot.

• How did the spoon handle get so hot?– Spoon handle hadn’t been

in the soup

Conduction?

• Can heat conduct through an object?

Conduction Experiment

• Materials– Aluminum and steel bars– Temperature strips– Plastic-foam cups– Large plastic cups

Temperature Strips

• Liquid-crystal temperature strips

• Crystals inside turn colors when they reach a given temperature

• Different crystals produce their colors at different temperatures

• No color if temperature is below 30˚C or above 36˚C

Conduction Through Materials

• “Conduction through Materials” worksheet

• Use the materials to complete the Observations and Conclusion section

The Results

1. The temperature strips displayed color after the metal had been in the hot water for awhile. Color indicates the temperature went up

2. Heat energy(molecular motion) in hot water molecules transferred to metal molecules, making them move more. Heat energy (motion) moved through the metal by energy transfer from molecule to molecule in the metal

3. Both metals conduct heat, Aluminum conducts better, heat moved up the bar faster.

How do you think….

• The Sun shines on Earth and the air gets warm. How do you think that happens?

How it happens….Radiant energy strikes Earth’s surface

The surface absorbs the energy

Surface molecules increase their motion

Molecules of air touches the heated surface of Earth

Energy is transferred from surface to the air

Another energy transfer

• Even more important way that heat energy enters the atmosphere

• Reradiation– Another way heat energy enters the atmosphere– Matter radiates heat and distributes it into the

atmosphere

Reradiation

• All matter radiates energy

Hot matter radiates more energy than cold

Reradiation• Sand, soil, water

& air absorb energy fromthe Sun - they warmedup

• When movedto shade they cooled down

Newspaper

Soil

Sand

Water

Air

Reradiatedthe energy that was absorbed to the air

What happens to the reradiated energy?

CO O

O

HH

Most reradiated energy is not visible, it is infrared (heat)

Infrared energy

Then transfers the energy to N2 and O2 in the atmosphere

To review…Earth ‘s atmosphere can be heated 3 ways

1. The atmosphere can absorb radiation directly from the sun

2. Air molecules gain energy when they come in contact with Earth’s surface

(conduction)3. Earth’s surface reradiates energy. Air

molecules (water and carbon dioxide) absorb radiant energy.

Conductor: a substance that allows heat to travel through it

easily

Insulator: a substance that prevents heat from traveling

through it easily

Reading

• Read “Heating the Atmosphere” starting on page 22.

• With a partner answer the “Think Questions” on page 26.