Why does a lot of hail, rain, or snow fall at some times and not others?

This 6th grade science unit on weather and climate builds toward the following NGSS Performance Expectations (PEs):

• MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
• MS-ESS2-4: Develop a model to describe the cycling of water through Earth’s systems driven by energy from the sun and the force of gravity.
• MS-ESS2-5: Collect data to provide evidence for how the motions and complex interactions of air masses results in changes in weather conditions.
• MS-ESS2-6: Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates.

The 6th grade science weather and climate unit expands students’ understanding of weather and climate, and the role of water in Earth’s surface processes which include these grades 6-8 elements of the Disciplinary Core Ideas (DCIs).  It addresses all but the crossed-out sections of the ones shown below. 

ESS2.C:  The Roles of Water in Earth’s Surface Processes

• Global movements of water and its changes in form are propelled by sunlight and gravity.
• The complex patterns of the changes and the movement of water in the atmosphere, determined by winds, landforms, and ocean temperatures and currents, are major determinants of local weather patterns.
• Variations in density due to variations in temperature and salinity drive a global pattern of interconnected ocean currents.
• Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land.

ESS2.D:  Weather and Climate

• Weather and climate are influenced by interactions involving sunlight, the ocean, the atmosphere, ice, landforms, and living things. These interactions vary with latitude, altitude, and local and regional geography, all of which can affect oceanic and atmospheric flow patterns. 
• Because these patterns are so complex, weather can only be predicted probabilistically.
• The ocean exerts a major influence on weather and climate by absorbing energy from the sun, releasing it over time, and globally redistributing it through ocean currents.

This unit builds on DCI elements that students should have developed in the prior OpenSciEd unit 6.2. These ideas are elicited and are used in new contexts (primarily different because of time and temporal scale). In many cases, the unit helps students extend these DCIs. The plain text beneath each of the DCI elements below describes how the ideas are used and where they are extended. 

• PS1.A: Structure and Properties of Matter:  Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. 
  • This particle model is reused and extended in Lessons 3-11, 13-14, and 17-18. It is used to model (1) how energy is transferred from the ground to the air (through conduction), (2) why air changes its density (due to changes in the speed of air particles), (3) why density would affect the amount of air pressure detected by a barometer (due to differences in the amount of force applied to the barometer from changes in the weight of a column of air particles overhead), and (4) how the cooling of water vapor in the air can cause the molecules in it to slow down enough that they stick to, rather than bounce off of, neighboring particles in collisions, thereby causing the particles to condense or solidify out of the air. 
• PS3.A: Definitions of Thermal Energy:  The temperature of a system is proportional to the average internal kinetic energy and potential energy per molecule (whichever is the appropriate building block for the system’s material). When the kinetic energy of an object changes, there is inevitably some other change in energy at the same time. 
  • The idea that thermal energy transfer can occur through conduction is used to explain how the air above the ground is heated by it, and how warm rising air cools off as it moves higher up, This idea is reused in Lessons 5-8, 10, 12, 13, 14, 17, 18, 20, and 22.
• PS4.B: Electromagnetic Radiation When light shines on an object, it is reflected, absorbed, or transmitted through the object, depending on the object’s material and the frequency (color) of the light. 
  • The idea that light is absorbed by the ground and converted to thermal energy is an idea that is reused in Lessons 3, 6-8, 10, 14, 17, 18, 20, and 22 in this unit.

Disciplinary Core Ideas are reproduced verbatim from A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. DOI: https://doi.org/10.17226/13165. National Research Council; Division of Behavioral and Social Sciences and Education; Board on Science Education; Committee on a Conceptual Framework for New K-12 Science Education Standards. National Academies Press, Washington, DC.

• Developing and Using Models
• Planning and Carrying Out Investigations
• Analyzing and Interpreting Data

• Patterns
• Cause and Effect
• Systems and System Models
• Matter and Energy

In this unit, students will need to have prior experiences in working with the ideas in the bolded sections of the related Common Core Math Standards listed below.

CCSS.MATH.CONTENT.6.NS.C.5: Understand that positive and negative numbers are used together to describe quantities having opposite directions or values (e.g., temperature above/below zero, elevation above/below sea level, credits/debits, positive/negative electric charge); use positive and negative numbers to represent quantities in real-world contexts, explaining the meaning of 0 in each situation.

CSS.MATH.CONTENT.6.NS.C.8: Solve real-world and mathematical problems by graphing points in all four quadrants of the coordinate plane. Include use of coordinates and absolute value to find distances between points with the same first coordinate or the same second coordinate.

CCSS.MATH.CONTENT.6.RP.A.2: Understand the concept of a unit rate a/b associated with a ratio a:b with b ≠ 0, and use rate language in the context of a ratio relationship. 

CCSS.MATH.CONTENT.6.RP.A.3: Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.

Additionally, when students generate and interpret the tables of data in Lessons 2, 4, and 11, they will draw on what they have learned across a number of Represent and Interpret data standards for grades 1-5, within the domain of Measurement and Data in the Common Core Mathematics Standards.

This is the third unit in 6th grade in the OpenSciEd Scope and Sequence. Given this placement, several modifications would need to be made if teaching this unit earlier or later in the middle school curriculum. These include the following adjustments:

• If taught before OpenSciEd Unit 6.2, supplemental teaching of the following would be required:
  • Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. 
  • The temperature of a sample of matter is proportional to the average internal kinetic energy per molecule in that sample.  
  • When the kinetic energy of a particle object changes, there is inevitably some other change in energy at the same time; kinetic energy can be transferred from one particle to another through particle collision. This form of energy transfer (conduction) can occur between solid, liquids and gases when they make contact with each other. 
  • When light shines on an object, it is reflected, absorbed, or transmitted through the object, depending on the object’s material and the color of the light.  Energy from the light that is absorbed by a sample of matter is converted to increased particle motion energy in that sample of matter.  
  • The total kinetic energy of particles in a sample of matter is also referred to as the thermal energy of that matter.
  • Identifying independent and dependent variables and controlling for other variables, can help you conduct fair tests, which is a necessary condition for producing data that can serve as the basis for evidence in supporting or refuting a potential cause and effect relationship in a system. 
• If taught before OpenSciEd Unit 6.1 (or at the start of the school year), supplemental teaching of classroom norms, setting up the Driving Question Board, and asking open-ended and testable questions would need to be added. Experience with using light sensors and reading and interpreting their output would need to be added.

• Michael Novak, Unit Lead, Northwestern University
• Renee Affolter, Writer, Boston College
• Emily Harris, Writer, BSCS Science Learning
• Audrey Mohan, Writer, BSCS Science Learning
• Lindsey Mohan, Writer, BSCS Science Learning
• Dawn Novak, Writer, BSCS Science Learning
• Tracey Ramirez, Writer, The Charles A. Dana Center, The University of Texas at Austin
• Abe Lo, Reviewer, BSCS Science Learning
• Katie Van Horne, Assessment Specialist
• Colleen O’Brien, Pilot Teacher, Williston Central School 
• Heather Galbreath, Pilot Teacher, Lombard Middle School
• Vanessa Hannana, Pilot Teacher, Indian Woods Middle School
• Whitney Smith, Pilot Teacher, Indian Woods Middle School
• Ann Rivet, Unit Advisory Chair, Teachers College, Columbia University
• Elisabeth Cohen, Advisory Team, Weather Outreach

BSCS Science Learning

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• Stacey Luce, Copyeditor and Editorial Production Lead
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• Valerie Maltese, Marketing Specialist & Project Coordinator
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An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has been identified as a quality example of a science unit. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.