Ann Bykerk-Kauffman of the department of geological and environmental sciences at California State University, Chico, explains how to make a cloud in a bottle to help students learn about cloud formation and the conditions that lead to it. This activity helps explain relative humidity and how it is affected by air temperature. Steps include, among others, lighting a match, tossing it into the bottle and topping it quickly with a rubber stopper. Students can observe the formation of a cloud when the stopper pops off under pressure.
B. Rivera, a chemistry teacher, uses a simple lab activity that records temperatures using wet and dry bulb thermometers to introduce relative humidity to his students. A significant difference between the temperatures on the thermometers indicates that the relative humidity is low. If the difference in temperatures is negligible, the humidity is high. A chart that accompanies the activity helps students identify the relative humidity in their classroom.
Relative humidity is closely related to the concept of dew point. In a lab activity designed by Price Laboratory School at the University of Northern Iowa, students use water, ice, a metal can and a thermometer to note the dew point. The dew point is the point at which the air is saturated and relative humidity is high enough to cause condensation or dew to form. This activity allows students to observe the condensation as it occurs.
Kathy Miles, writing for starryskies.com explains how students can create fog in a bottle. Using two narrow bottles, some ice and some hot water, they can create fog. The lab activity helps illustrate how fog forms and under what conditions. This particular activity demonstrates how radiation fog, or fog that results when the cooler air descends over warmer air, forms.