How Does Convection Happen In Our Atmosphere?

What makes the sky clear or without clouds?

Objectives

Concepts:

• Convection is the organized motion or movement of large groups of molecules based on their relative densities or temperatures.

  For example, convection is the upward motion of a warm fluid spreading through a cooler one.

• Weather is the state of the atmosphere and conditions such as dry or wet, cold or hot, stormy or calm, cloudy or clear.

  In plain terms, we can say that weather happens when wet air goes up in the atmosphere.

Principles:

• Weather activity happens when wet air goes up into the atmosphere and cooler air comes down from the atmosphere.

• One cause of rising air in our atmosphere is from the process called convection.

• Warm air rises above cold air by convection.

• Clouds form when water vapor condenses and molecules cling to each other.

• While convection is happening and warm moist air is going upwards, there is also the sinking of denser and cooler molecules from the sky moving downward.

Facts:

• Convection happens because warm air is less dense than the cold air around it, so it is lighter and rises or goes up in the atmosphere.

• Evidence of convection happening is seen with the formation and growth of cumulus clouds.

• We see evidence of sinking motions of heavier and cooler air falling to the earth when the sky is clear or without clouds.

• Warm and moist air rises and forms clouds in our sky.

• There is a constant balancing act going on all the time in our atmosphere as moist, warm air goes upward and cooler, denser air moves down. Air is constantly moving upward and downward, creating our "weather."

Skills:

• Following directions
• Making observations
• Making inferences
• Drawing conclusions
• Forming generalizations
• Communicating findings

Materials

1. Large glass jar without a lid
2. Small glass jar with a lid (which fits inside larger jar)
3. Plastic drinking straws
4. Dark food coloring
5. Hot water in large pouring container
6. Cold water in large pouring container
7. Hammer and large nail to make holes in lids of small jars
8. Scissors to cut straws into 2-inch pieces
9. Rulers
10. Pen
11. Paper towels or sponge
12. Handout

Room Preparation

Water activities are often messy activities! Each student (or pair) needs a work area in which to do their own experiment. Water is likely to spill, so remove any materials that should not get wet from tables or desks. Also, have paper towels or sponge ready to clean up tabletops and floors.

Safety Precautions

If students use hammer and nails to make two holes in their small jar lids, review safety rules and how to make holes. Exercise caution and review safety concerns when students fill small jars with hot water. Remind students to be careful when adding food coloring drops to small jars. Food coloring may stain clothes.

Procedures and Activities

Introduction

What do we see when we look up into the sky? Sometimes we see a mass of clouds, sometimes some clouds and some clear sky, and sometimes nothing but clear sky everywhere.

Today, we are going to do an experiment to help us understand:

1. What is convection?
2. How does convection happen in our atmosphere?
3. How do clouds form?
4. What makes the sky clear or without clouds?

Activity

1. Pass Out Materials Provide each student or pair with large jar, small jar with lid (you may have already punched two holes in lids), plastic straw and scissors. If students punch holes in lid, you will need to give them a hammer and a large nail.

2. Make 2 Holes in Small Jar Lids or Pass Out Lids Already with Holes Show students how to use the hammer and large nail to carefully punch 2 holes in the lid of the small jar. These holes should be just large enough to hold a piece of the straw snugly. Be careful not to make holes so large that the straws fall through.

3. Cut Straws into Two 2-Inch Pieces Have students use ruler and pen to measure and mark straw to make two 2-inch pieces. Have students cut on marks. Set aside straw pieces.

4. Put Straws into Lid Holes Students put one piece of straw in each hole. One piece of straw should be placed so that about half an inch is above the top of the lid. The other straw piece should be placed so that about half an inch is below the lid.

5. Food Coloring in Small Jar Have students put a few drops of dark food coloring in the small jar.

6. Hot Water in Small Jar Pour or have students pour hot water into small jar until it is full. Screw on lid of the jar. Make sure 2 straw pieces are properly placed. Put small jar aside.

7. Cold Water in Large Jar Pour or have students pour cold water about 3/4 full in the large jar. Remind students that they will put small jar in large jar. Go over water displacement—if large jar is full of water, when we put small jar in it, the cold water will rise and spill out.

8. Place Small Jar of Hot Water into Large Jar of Cold Water Carefully place the small jar into the big jar. Be sure the cold water completely covers the top of the higher straw. If not, add some cold water to large jar until straws are covered.

9. Observations, Drawing Conclusions & Forming Generalizations Carefully observe what is happening. Where is the colored water from the small jar of hot water going? What happens to the colored water when it reaches the top of the small jar? What happens when colored water gets out of small jar and into the cold water of the large jar?

10. Communicating Findings Have students take time out to draw and answer questions found on the handout. Have them work in pairs or small groups to prepare a summary of what they did and what they think happened. Share that this process is "communicating findings": a very important part of a scientist's job, so she or he can tell others what they did and what they think they found out.

Closing - Original Questions

Ask again:

1. What is convection?

2. How does convection happen in our atmosphere?

3. How do clouds form?

4. What makes the sky clear or without clouds?

Evaluation

Have students take turns sharing with each other:

• What our original questions were
• What experiment we conducted
• Our observations and findings
• And finally, our answers (conclusions & generalizations) to the original questions

Extension Ideas

Have students repeat their experiment to make sure that their observations, findings, generalizations, and conclusions are accurate. Share that experiments have to be replicated many times to be sure that findings are true. Review the importance of following directions precisely so you do not change or alter variables that may, in turn, change the experiment's results.

Let students come up with similar experiments which do purposefully alter variables. For example, they may put hot water in large jar and cold water in small jar. Have them document just what materials and steps they followed, what they observed, and what their conclusions and findings are. Then they may compare the two experiments and results, offering explanations for similarities or differences in their findings.

Explore Images and Animations Illustrating Convection from the Jet Propulsion Lab.

Look over other activities from CAPS: Does the Sun Influence the Temperature of the Earth?, Reading a Thermometer, Keeping a Daily Weather Log, What Is Heat Transfer?, and What is Temperature?

Careers Related to the Lesson Topic

• Aerospace Engineer
  • Tour - Aerospace Labs and Wind Tunnels
• Anyone with a Job Outdoors
• Environmentalist
  • Career Presentation - Lynda Asher
• Environmental Engineer
• Farmer
• Meteorologist
  • Tour, Weather Underground at University of Michigan's Department of Atmospheric, Oceanic, and Space Sciences
• Naval Science & Engineering
  • Career Presentation: Mike Riordan
• Pilot
  • Tour - Yankee Air Museum
  • Job Shadowing, Pilot, Flight Instructor - Burt Lamkin
• TV or Radio Weather Reporter

Let us know what you think!

Mark Palmer University of Oklahoma Center for Analysis and Prediction of Storms (405)-325-6079 [email protected]

Webmaster (Martha)

Prerequisite Vocabulary

Convection The organized motion or movement of large groups of molecules based on their relative densities or temperatures.

Weather The state of the atmosphere and conditions such as dry or wet, cold or hot, stormy or calm, cloudy or clear. Updated 18 Jan 01

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