HEAT TRANSFER

Investigation 4Weather and Water

INVESTIGATION 4 Part 1

WORD PLAY

Heat Radiation Conduction Temperature

WHAT IS HEAT?

In your journal – tell me what heat is, can you hold it?

How do you “get” it? How do you “acquire” heat?

What’s happening on the molecular level when there is “heat”?

How does heat get from one thing to another thing?

JOURNAL QUESTIONS

When we check a weather report to find out the temperature, what are we finding the temperature of?

When do you think it is hottest during the day? Why?

When is the coldest? Why? Where in our local environment might it be the

very hottest during the hot part of our day/ Do you think the surface of Earth affects how

hot the air gets?

WHAT HAPPENS TO DIFFERENT EARTH MATERIALS WHEN THE SUN SHINES ON THEM?

What is an earth material? What is the main source of energy

that could heat these earth materials?

WATER IS SPECIAL

If each earth material received the same amount of solar energy, how can you explain the differences in temperature?

Water has an important property. It takes 5x the heat energy to raise an amount of water one degree than it takes to raise the temperature of an equal amount of dry soil or sand one degree. When the same amount of heat energy is absorbed equally be all materials, the temperature of the solid earth materials goes up faster than water.

WATER IS SPECIAL CONT.

If a kilogram of water and a kilogram of soil absorb equal amounts of solar energy, the temperature of the soil will be much higher that the temperature of the water. The water doesn’t get as hot, but it has absorbed the same amount of heat energy.

water soil

1 C 5 C

CONSIDER THE FOLLOWING…

water soil

1 C5 C

Why is this a good thing

for our earth?How does this

relate to global

warming and our earth?

ENERGY What kind of energy heated up the earth

materials? How did the energy get from the sun to the

materials? Energy comes from the sun as radiant

energy. Radiant energy travels as waves through space and through air. Radiation from the sun can be visible like ________, or invisible like _________, ___________, __________, ________, ________ and other wavelengths.

RADIATION ON THE MOLECULAR LEVEL

When radiant energy strikes an atom or molecule, like a water molecule or a molecule in sand, soil, or air, the molecule gains energy and begins to move faster or vibrate more. We say the molecule absorbed the radiant energy. Absorbing radiant energy is one way energy transfers to matter.

Molecular motion is heat. The more motion there is in the molecules of matter, the hotter it is.

That’s Hot!

LET THE SUN SHINE!

Radiation is one way energy can travel over great distances or short distances. When you stand in the sunshine, you are receiving energy from 150 million kilometers away. When you reach out to warm your hands at a campfire, radiant energy given off by the blaze a meter or two away is absorbed by molecules in your skin, and your hands warm up.

EVEN THROUGH SPACE…

Radiant energy travels through the vacuum of space, and some wavelengths travel through air and other transparent materials, like glass, plastic, and water. Radiant energy is energy transfer at a distance without direct contact b/t the energy source and the energy receiver.

DIFFERENTIAL HEATING

Different materials heat up at different rates. This is called differential heating. Differential heating accounts for the difference in the temperature of water and soil after they have both been in the sunshine for the same length of time. Water in oceans and lakes can store more heat than can landmasses, even though the temperature of the water may be lower.

INVESTIGATION 4/PART 1 WRAP-UP

Heat and Energy Animation Read “Thermometer: A Device to

Measure Temperature.” on pg. 20-21 and complete the thermometer worksheet.

INVESTIGATION Part II

CONDUCTION

Let’s review: What is radiation? How does radiation affect the surface

of Earth?

RADIATION REMEMBERS

Radiation is energy that passes through space. Earth receives radiation from the sun. Radiation comes in different wavelengths

Visible light Infrared Ultraviolet microwave, X-Ray Radio

Radiation is transferred w/o direct contact.

VISIBLE LIGHT

Visible light is the main kind of energy from the sun that heats Earth. Energy is transferred when light energy is absorbed by molecules in Earth’s surface, causing them to move faster, which increases temperature.

CONSIDER THE FOLLOWING…

Think about an 85 degree sunny day – you’re walking barefoot on a sidewalk…

What did you feel? Why did your feet feel hot? How did heat transfer from the

cement to your feet?

YOUR CHALLENGE

You have some water that is about 30 degrees Celsius – too cold.

I thought I would warm it up by mixing it with some of this hot water, but this hot water has salt and red coloring in it. I don’t want any salt or red in my cold blue water.

And these are the only materials. How can you warm up the blue water with

only these materials?

THE RULES

Each group can have two cups, two vials, and four thermometers.

When you have decided on the procedure you will use, obtain some red hot water and some blue cold water.

Keep records of your procedure and data as your experiment progresses using your lab sheet.

YOUR QUESTION

How can you warm the cold blue water without mixing it with the hot red water?

You can only use the following materials for warming purposes… Cold water Hot water Plastic cups Foam cups Vials thermometers

DIDJA DO IT?

Was your group able to raise the temperature of the cold water?

How were you able to do this? How did heat transfer from the hot

water to the cold water?

CONDUCTION EXPLAINED

First of all, there was no cold, only heat. What we perceive as cold is actually low levels of heat. When you hold an ice cube in your hand, cold doesn’t go into your hand, energy goes out of your hand into the ice cube.

Heat is the motion of atoms and molecules. The greater the motion, the more heat energy there is a solid, liquid, or gas.

CONTINUED

When material 1, with lots of heat or molecular motion, comes in contact with material 2, which has less molecular motion, the energized molecules in material 1 bang into molecules in material 2 and get them moving faster. As a result, molecules in material 2 is now hotter. Molecules in material 1 have less motion (heat) so material 1 is now cooler.

CONDUCTION

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

What is called when heat is transferred w/o contact?

This kind of heat transfer is conduction. Heat can transfer by conduction from atom to atom in a material, or b/t 2 different materials when their atoms or molecules make contact.

Multimedia time - Conduction

ENERGY DIAGRAM

Analyze the energy experiment you completed by drawing an energy diagram, starting with hot water to the alcohol in the thermometer.

Does your diagram look like this?

Hot water

Plastic vial

Cold water

Glass of

thermom

Alcohol in

therm

JOURNAL QUESTIONS

1. Write a definition for heat.2. Describe heat conduction.3. Explain your understanding of how

heat transfers from one material to another.

4. Explain why a pop can feel cold when you take it out of the refrigerator.

5. Draw an energy diagram of the pop from refrigerator to your hand.

THERMOMETER ANIMATION

CONSIDER THE FOLLOWING… Did you ever reach for a metal spoon

that was in a pot of cooking soup? If so, you might have been surprised to find that it was really hot. But the spoon handle was not in the soup.

How did the handle of the spoon get so hot?

Let’s investigate…

CONDUCTION INVESTIGATION

Question: Does heat energy transfer through solids?

Materials: Aluminum and steel bars Temperature strips Thermometers Foam cups Large plastic cups tape

TEMPERATURE STRIPS

This is a liquid-crystal temperature strip. The crystals sealed inside turn color when they reach a certain temperature. Different crystals produce their color at different temperatures.

Some crystal colors turn on when the temperature reaches a certain level, and turn off when the temperature goes higher than that.

The temperature strips on the metal bars will allow you to “see” conduction in action.

CONDUCTION INVESTIGATION

WS 19 – Conduction through Materials Use your Lab Sheet to record your

investigation.

INVESTIGATION QUESTIONS

Please answer these questions on paper to attach to your lab sheet.

1. What happened when the metal bars with temperature steps were placed in the hot water?

2. How did heat get from the hot water to the temperature strip far above the water level?

3. Did the metals conduct heat? Which metal is a better conductor of heat? What evidence do you have that supports your answer?

Time for the Conduction Video!

CONDUCTION AND EARTH’S SURFACE The sun shines on Earth and the air gets warm. How

does that happen? Draw an energy diagram for the following:

Radiant solar energy strikes Earth’s surface. The surface absorbs the energy.

Molecules in the surface materials increase their motion. Motion is heat, so the surface heats up.

Molecules of gases in the air come into contact with Earth’s heated surface.

If the surface is warmer than the air, energy from the surface will transfer to the air molecules. Air molecules will increase their motion. Motion is heat, so the air heats up.

Energy Diagram – Does yours look like this?

Motion is heat so

air heats up

Molecules in gases heat up

Molecules in

surface increase

in motion

Surface absorbs energy

Radiant Energy

Surface heats

up

Air or Land heats up depending on which is

warmer

CONDUCTION

Conduction is one way energy transfers to the atmosphere. When air molecules come in to contact with hot surfaces, they receive energy and get hotter.

But wait! There’s more!

RERADIATION

There is another, even more important way that heat energy enters the atmosphere. It is called reradiation.

All matter radiates energy. I t is one of the great truths of nature. Hot matter radiates more energy than cold matter.

When matter, like sand, soil, or water, absorbs energy from the sun, it warms up. When that hot matter reradiates that energy, the matter cools down. That’s why your containers of earth materials cooled down when you moved them to the shade – they reradiated the energy they had absorbed from the Sun.

RERADIATION CONTINUED…

What happens to the reradiated energy? Most reradiated energy is not in the visible spectrum; it is in the infrared part of the spectrum. Infrared radiation is absorbed water and carbon dioxide molecules in the atmosphere. The energized water and carbon dioxide molecules then transfer their energy by conduction (contact) to the oxygen and nitrogen molecules in the air to heat the whole atmosphere.