Lab Activity for Radiation, Convection, & Conduction

Introduction

Lab Activity #1: The Atmosphere in a Cake Pan

In this activity, we model the air movements that happen when the ground heats the atmosphere and how that heat moves through the atmosphere. We use water to represent air in the lower part of the atmosphere (i.e. the troposphere) because it's easier to observe the motion of water than it is to observe the motion of air. Keep in mind, however, what each part of the model represents:

 Part of Model Real Thing That it Represents Bottom of cake pan The Earth's surface Water in the cake pan The lowermost layer of the atmosphere (the troposphere) Air above the cake pan The stratosphere (the  layer  of  the  atmosphere  directly above the troposphere) Bag of ice Cold upper troposphere Candles Ground heated by radiation

Materials:

large rectangular clear glass cake pan (15x10x2)

red and blue food coloring

small candles (the kind that are used to keep food warm)

box of matches

three beakers

Ice in a gallon-size Ziploc

Activity

a.   Place the small beakers upside down on the lab table, forming a triangle that the cake pan can rest on and remain stable. Place the cake pan on the three beakers.

b.   Fill the cake pan with water.

c.   Light the candles and place them in a line underneath one end of the cake pan.  This end of the cake pan represents the surface of the earth.

d.   Put some ice in the large Ziploc bag and place the bag of ice in the cake pan on  the side opposite the candle. This end of the cake pan represents the upper atmosphere of the earth.  The setup should look like the diagram below.

Questions

1.   Before you add the food coloring, in which directions do you think the water will move and why?

e.   After the cake pan has rested undisturbed for a few minutes, CAREFULLY place several drops of blue food coloring in a line along the bag of ice, near where it touches the water on the surface.

f.   Carefully place several drops of red food coloring into the water in a line along the BOTTOM of the cake pan directly above the candles

g.   Watch the motion of the colored water and answer the following questions.

2.  Describe the movement of the two colors?

3.   Please explain why you think the colors moved like they did.

4.   What can you conclude about the density of the water near the candle as  compared to the density of the water near the ice? Where is the water more dense? Why?

5.  How does this activity demonstrate radiation, conduction, and convection?  Explain where each is demonstrated.