A shockingly high number of my students (and, back when I taught high school kids, a shocking number of high students) have asked me about fog. What causes it? Where does it come from? Is it weather, or a bunch of ghosts hanging out together? (See what I mean about the high high school students?) This handy dandy Demo Science science demo will help you show your students how fog forms and how it relates to other weather phenomena.
The All-New Fog-O-Matic 2700
For this experiment, you’ll need a large jar (the bigger the better), a strainer, water (as hot as you can reasonably and safely get it), and iced cubes (as cold as possible). Fill your jar with hot water and let it sit for 30 seconds to a minute; then, pour out most of the water, leaving about an inch at the bottom.
Put your strainer over the mouth of the jar, then load up the strainer with iced cubes. Give it a moment, et voilà: fog! How did you do that? Are you Storm from X-Men or what?
Moisture + Temperature = Fog
It’s simple math, really. And by “math,” I mean “science.” For fog to occur naturally, the air must be saturated, or have a relative humidity close to 100%. Hence, the jar full of water in the first step. Fog most often occurs when warm, moist air travels over land, water, or another air mass that is cooler than it is. Hence, the iced cubes. The cold air the iced cubes created around themselves caused the warm, moist air inside the jar to condense, forming fog.
Fog frequently leads to condensation, and sometimes even rain. This can temporarily alter an area’s water levels and may even influence that area’s ongoing water cycle.
Photo credit: Foter.com