Grade level
Planning and Carrying Out Investigations
Cause and Effect
ESS2.C: The Roles of Water in Earth's Surface Processes
Students engage in a demonstration to better understand why some clouds produce rain and others do not. For the demonstration, water in a cup represents the atmosphere and shaving cream on top of the water represents the presence of clouds. Students keep track of how much blue food coloring must be added – representing additional moisture – in order for the shaving cream to become saturated enough to deposit the liquid dye into the ‘atmosphere’ below.
Students all experienced a sense of awe at the moment in which they started seeing dark blue food coloring penetrating the shaving cream and moving into the water. The samples show a range of thinking with two salient points of view: 1) Some students saw the increase in water vapor as a concentrated point of force. For example, in Sample A the student is talking about how the drops bore a hole into the shaving cream making it go into the ‘atmosphere’; and 2) the more common viewpoint was showing an early understanding of saturation point (Samples B-D). In Sample B, the student states, “It can’t handle that much water”. In Sample C, the student makes a loose connection between the amount of added moisture and the severity of the rainfall (e.g. sprinkling). And in Sample D, the students’ thinking reflects an understanding of a tipping point in which the cloud becomes full of water vapor to a point and then “drop[s] all of the rain.”
Further questioning of these students might better elicit what they see as an affordance and a constraint of the physical model that was used during this investigation. That is, how does this represent a cloud and atmosphere system and in what ways might the procedures or set-up be changed to better reflect this system?
