Learn How to Form Fog
Discover how air temperature and humidity work together to make condensation, dew, and fog.
Before You Play
This experiment works best when the air has some moisture in it. If the air is very dry (static electricity in hair, sparks when touching metal door knobs, etc.), there is little water vapor in the air. You will have to drop the temperature in the room below freezing before dew or condensation would form. You may want to try the experiment first to make sure your child will get satisfactory results.
Talk to your child about what fog looks like. Ask, "Where have you seen fog? What was it like?" Tell your child that today he’s going to do an experiment that will show what temperature it has to be in the room for moisture in the air to form fog. If possible, watch the Cyberchase episode “Gone with the Fog” with your child.
Materials
Directions
Explain that fog forms because warm air holds more moisture (water vapor) than cold air, and as air cools, the water gets “squeezed out.”
Oversee your child as he does the experiment according to the directions on the “Let’s Dew It!” printable. After each ice cube is added, your child should watch the thermometer to see the water temperature drop. That way, he will be ready to note the temperature once the water is cool enough for condensation to form on the can.
Once your child has finished his experiment, talk about his findings. Ask, “How much would you have to lower the temperature in the room to make fog form?”
Math
Science