To do this project, you will need to study what makes fog and how extreme changes in temperature between air, land and water vapor work together to produce the effect. Choose a very cold day, with temperatures below freezing. Fill a heat proof measuring cup with one cup of boiling water. Take the cup outside and toss the water into the air. You should see the hot water instantly turn into a puff of fog. Do this several different times with different water temperatures and document your results in a science journal. Use a video to record each test with the different temperatures of water and show the video during your science fair as a part of your display. Parental supervision is needed for this project.
Dry ice makes fog because of its extremely cold temperatures. When it comes in contact with water it creates a true cloud of water vapor or fog. The hotter the water, the more fog is produced. To make fog with dry ice, have a demonstration area available at your science fair in front of your science board with facts written about fog and how dry ice works. For each 15 minutes of fog, you'll need five to ten pounds of dry ice and four to eight gallons of hot water. Have a small fan on hand to demonstrate how fog without steam will flow down hill in the direction of any wind that is present in nature. Show how smaller pieces of dry ice with more surface area produce more fog while larger pieces produce less fog. Keep your water hot with a coffee pot or hot plate, or you'll need to refresh the hot water from the tap often to keep it hot enough to produce lots of fog. Adult supervision is required for this project, and dry ice should be handled only while wearing work gloves.
To make fog, you will need two soda bottles with necks about the size of an ice cube, some hot and cold water and a science journal. Empty and rinse the soda bottles and label one with "cold water" and other with "hot water." Fill the cold water bottle one quarter full with cold water and place an ice cube in the neck of the bottle. It should be wedged in so that it does not pass all the way through the bottle. Observe what happens in the bottle and record your findings in your science journal. Repeat the steps with the second bottle, but this time use hot water. Note what happens in your science journal. Fog should form in the bottle with hot water and not in the cold water bottle. Record in your journal why you think this happened.
For this science project, use a journal to track the formation of fog over the course of two months. Do this research during times when the weather is the most changeable, such as spring and fall. Record the outside temperature at the same time each night and each morning and makes notes about how much fog you see or if there is any fog at all. Record observations such as whether the skies are clear or cloudy, how much wind is present and its speed and direction and other weather conditions you may want to include. Chart your observations and highlight the clear patterns of when the fog occurred. Draw conclusions based on the patterns as to when you are most likely to see fog. Prepare your display board with your charts, your fog journal and your summary.