The Rain Man

National Weather Service/NOAA
Type Category
Instructional Materials
Model , Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This is an activity that is part of a larger unit on the Hydrologic Cycle. Students create “precipitation” by suspending a bag of ice over a container with hot water. The water vapor in the air condenses on the bag. When enough water accumulates the water begins to join together and will eventually drip back into the container.

Intended Audience

Educational Level
  • Grade 8
  • Grade 7
  • Grade 6
  • Middle School
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-ESS2-1 Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.

Clarification Statement: Emphasis is on the processes of melting, crystallization, weathering, deformation, and sedimentation, which act together to form minerals and rocks through the cycling of Earth’s materials.

Assessment Boundary: Assessment does not include the identification and naming of minerals.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
This activity serves as an aid in understanding one part of the water cycle – precipitation. This activity should be one of several that a student engages in. Other activities should include transpiration, runoff, condensation, and evaporation. Although the focus of the activity is precipitation, it should be noted that condensation also occurs. When doing this activity ask questions such as, Where did the water that is dripping from the bag come from? Students may have the misconception that the water comes from the bag of melting ice. The bag could be weighed before and after to show water isn’t leaving the bag. Students should think about the changes in energy the water molecules undergo. Why does the water evaporate? What causes the water to condense or become a liquid again? Why does water drip off the bag? Questions and discussions about how this activity relates to cloud formation and eventually rain should also be included so students can start relating these processes to the water cycle. Students are not developing a model for precipitation, rather they are replicating an already established model. However, if students are asked to draw and describe what is happening to water molecules for evaporation, condensation, and precipitation to occur, they would be developing a model. There would need to be a discussion with students about the role of gravity and then how this model serves to represent how precipitation forms in clouds – water first has to condense and enough needs to accumulate so it can fall. This activity itself doesn’t include the role of the sun and its energy in driving this part of the hydrologic cycle but should be a part of the discussion.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
This is a model shows that water will condense on a cool surface and when enough accumulates together will drop to the ground (precipitation). Students should take this model and develop a model such as a drawing that more fully explains the processes that occur with water molecules that leads to evaporation from the liquid in the beaker, condensation onto the bag of ice, joining together with others and eventually dropping back into the beaker. The model should be able to help explain: where did the water come from that collected on the bag?, why did the water collect on the bag, why does the water drip into the beaker? Students should then relate these processes to what happens in a cloud by building another model.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
This activity focuses on precipitation but can also lead to a discussion of condensation and evaporation as those processes are also occurring in the activity. Other activities would be needed to address other aspects of the water cycle, transpiration and runoff, in order to fully address the disciplinary core idea and then pulling the ideas learned altogether to develop a full understanding of the water cycle. Students should also relate the process observed to what actually happens in the atmosphere. Water vapor evaporates from bodies of water (water evaporating from the warm water in the container) and then condenses to form clouds which are composed of very small water droplets. When enough of those water droplets gather together (like when enough water condenses on the bag over the container) they begin to fall due to gravity.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
Phase changes are integral to the processes involved in this activity but the energy transfers are not discussed. Although not asked to do in the activity, students should create a model (drawing) what is happening to the water molecules throughout the processes. Students should be made aware that the water in the container is hot. They should think about why some of the water molecules become a gas (some of the water molecules move fast enough to become a gas). As those fast moving water molecules contact the plastic they transfer some of their energy to the plastic and the cold, slower moving water molecules in the ice. The water vapor molecules begin to move more slowly (their temperature decreases). When the molecules slow enough they become a liquid on the surface of the plastic. This then needs to be related to the process in the atmosphere where water vapor molecules lose energy to the other molecules in the air and at some point move slowly enough to condense on condensation nuclei to form clouds. When enough of these molecules collide with each other they become heavy enough to be pulled down by gravity like in this model where enough condensed water gathers together and then drops back into the container.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This is an activity that would be part of a larger unit associated with the Performance Expectation. As written, the activity doesn’t fully support all three dimensions but additions can be included to prove a more 3-dimensional learning experience. The activity itself has students focusing on one aspect, precipitation, although evaporation and condensation are also taking place in the activity. It does have students using a model for this one part of the hydrologic cycle so it does involve parts of 2 dimensions: developing and using models and the roles of water in Earth’s surface processes. It could involve the 3rd dimension if students were to create a model (drawing) showing the transfer of energy causing the water molecules to become a gas, the transfer of energy causing the molecules to become a liquid and gravity pulling on the water causing them to drip into the beaker. This would then strengthen the activity by describing how energy drives the system of evaporation and condensation. The alignment to NGSS also becomes stronger as students do several activities that build their understanding of the hydrologic cycle and eventually use the information to develop a model of the movement of water in the atmosphere.

  • Instructional Supports: The activity is simple and supports understanding of phenomena by using a visual model. The information provided is more on how to do the activity rather than how to use the activity to more thoroughly understand this one aspect of the hydrologic cycle. It could be strengthened by having students explain how precipitation is part of a larger process, the hydrologic cycle. Also precipitation is something students should be familiar with and would be a great way to differentiate since there is no guidance on differentiation. Students could be asked how precipitation affects their lives, they could draw pictures, and could read information about rain written at different levels.

  • Monitoring Student Progress: This aspect is weak. There are no clear instructions on how to determine whether students are progressing or if they have a clear understanding of the concepts involved. Having students create a model of what is occurring as the water molecules gain energy (leading to evaporation), transfer their energy (slowing and eventually becoming liquid) and gather together and fall (precipitation) would also be valuable to in determining if students are making sense of the process. Students should explain and draw the processes being exhibited by the activity, creating a model. This would allow the instructor to see if the students truly understand the processes that are occurring. Assessments would need to be created by the instructor.

  • Quality of Technological Interactivity: This resource has no technological component.