Abstract

Objective

In this experiment you will investigate how pressure in the atmosphere is linked to the formation of clouds by making a cloud chamber.

Project Note: January 2009 It has come to our attention that there are problems with the Procedures in this project, and we can no longer recommend it as a good science fair project. If you need help choosing another project please try our Topic Selection Wizard. We apologize for any inconvenience.

Introduction

Why is it that on a cold day we can see our breath? The answer is that the air we breathe out contains moisture in the form of water vapor. When that warm, moist air meets the cold, dry air outside, a cloud forms.

There must be three main ingredients present in order for clouds to form (UCAR, 2000):

• Moisture - There must be sufficient water vapor in the air to build a cloud.
• Cooling air - The air temperature must decrease enough for water vapor to condense.
• Condensation nuclei - Tiny particles, invisible to the human eye, such as dust, dirt, and pollutants, provide surfaces on which water molecules can gather and condense into water droplets.

If the conditions are right, then a cloud will form. Clouds often form where two weather fronts meet, like when a cold front meets a warm front. The kind of clouds that form can say a lot about what type of weather is coming! The main kinds of clouds are stratus, cumulus, and cirrus clouds, and each one forms under different conditions.

Clouds (www.free-pictures-photos.com/clouds, 2006).

In this experiment, you will make your own cloud by making a cloud chamber. Inside the cloud chamber, you will provide the right conditions for a miniature cloud to form! What will happen to your cloud if you change some of the conditions?

You can make your very own cloud chamber to study cloud formation! (Exploratorium, 1997)

Terms, Concepts, and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• clouds
• atmosphere
• pressure
• humidity
• water vapor

• How do clouds form?
• Does atmospheric pressure increase or decrease the formation of clouds?
• How are clouds nucleated by particles in the atmosphere?

Bibliography

• This project was adapted from a project in the Exploratorium Science Snacks:
  Exploratorium, 1997. "Fog Chamber," San Francisco, CA: Exploratorium Museum. [accessed September 29, 2006]
  http://www.exploratorium.edu/snacks/fog_chamber.html
• This site from USA Today has a whole section devoted to clouds. Read about the different kinds of clouds, and how they help inform meteorologists:
  USA Today Staff, 2005. "Understanding clouds and fog," USA Today. [accessed September 29, 2006]
  http://www.usatoday.com/weather/wcloud0.htm
• UCAR, 2000. "Web Weather for Kids: Clouds," University Corporation for Atmospheric Research (UCAR). [accessed September 29, 2006]
  http://eo.ucar.edu/webweather/cloudhome.html
• De Paola, T., 1984. The Cloud Book, New York, NY: Holiday House.
• Bohren, C., 1987. Clouds in a Glass of Beer, New York, NY: John Wiley & Sons.

Materials and Equipment

• large pickle jar or other large wide-mouthed jar
• latex gloves
• matches
• water

Experimental Procedure

1. First, you will need to learn how to make a cloud chamber using the jar, glove, match, and water.
2. Barely cover the bottom of the jar with water.
3. Hang the glove inside the jar with its fingers pointing down, and stretch the glove's open end over the mouth of the jar to seal it.
4. Insert your hand into the glove and quickly pull it outward without disturbing the jar's seal. Nothing will happen.
5. Next, remove the glove, drop a lit match into the jar, and replace the glove. The match will go out and create smoke particles in the jar which will become nucleation sites.
6. Pull outward on the glove once more. Fog forms inside the jar when you pull the glove outward and disappears when the glove snaps back. The fog will form for 5 to 10 minutes before the smoke particles settle and have to be replenished.
7. Now that you know how to make a cloud in a jar, you can experiment with different conditions that lead to cloud formation. You can change several things in your experiments, including:

   Variable	How to change it:
   air pressure	to increase - start the glove on the outside and push it into the jar to decrease - start the glove on the inside and pull it out of the jar
   nucleation	more nucleation - drop more lit matches into the jar less nucleation - drop fewer lit matches into the jar
   temperature	to increase - place the jar in a pot of hot water to decrease - place the jar in a tray of ice
   humidity	to increase - add more water to the jar to decrease - add less water to the jar

8. You will need a data table to keep track of your experiments, what you change and what the results are. Here is an example of how to organize your data:

   Trial	Glove	Match	Water	Cloud (None, Small, Medium, Large...)
   1	Inside	No	Yes
   2	Inside	Yes	No
   3	Inside	Yes	Yes
   4	Outside	No	Yes
   5	Outside	Yes	No
   6	Outside	Yes	Yes

9. For each variable you try, you will need to make a graph and evaluate your data. Make a scale to evaluate the clouds that form based on size (none, small, medium, or large). Then you can look for variables that either increase or decrease cloud size.
10. Which factors are important or necessary for clouds to form? Which variables when changed resulted in a change in cloud size? How do you think these processes work together?

Variations

• Try making observations of clouds in the sky. Can you identify the different types of clouds? Can you correlate the appearance of different types of clouds with weather patterns? For example, are there more cumulus clouds or stratus clouds during a thunderstorm?
• Cloud formation is a part of the water cycle, where water from lakes and oceans evaporates into the atmosphere. This is where the water vapor comes from that makes clouds in the atmosphere. You can compare evaporation from salt water and freshwater to find out if there are any differences. You can measure the amount of evaporation by heating a known volume of water at a particular temperature (measured with a thermometer) for a particular period of time (measured with a timer) and calculate the difference in volume before and after (measured in milliliters). Which body of water evaporates more readily, salt water or fresh water?

• For more science project ideas in this area of science, see Weather & Atmosphere Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

This project was adapted from a project in the Exploratorium Science Snacks:
Exploratorium, 1997. "Fog Chamber," San Francisco, CA: Exploratorium Museum. [accessed September 29, 2006]
http://www.exploratorium.edu/snacks/fog_chamber.html

Last edit date: 2009-05-12 00:00:00