Lesson 3: Where Does Matter Go? Modeling Invisible Processes
Duration of Days: 3
Lesson Objective
Students will develop a conceptual model of matter flow within the tank system by identifying how waste is transformed, introducing the role of bacteria, and constructing a flow diagram that explains how substances move and change within the system.
If matter cannot disappear, where does it go?
What happens to waste in a closed system?
What organisms exist in the tank that we cannot see?
How do bacteria contribute to system stability?
How do plants and microorganisms interact chemically?
Matter
Transformation
Ammonia
Nitrite
Nitrate
Nitrifying bacteria
Decomposition
Conversion
Biological filtration
Microorganism
HS LS2 4
Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.
HS LS2 5
Develop a model to illustrate the cycling of matter among living and nonliving components of an ecosystem.
Science and Engineering Practice, Developing and Using Models
Science and Engineering Practice, Constructing Explanations
Science and Engineering Practice, Analyzing and Interpreting Data
Crosscutting Concept, Systems and System Models
Crosscutting Concept, Energy and Matter
Crosscutting Concept, Cause and Effect
Students interpret diagrams and translate them into written explanations.
Students trace logical sequences across multiple steps.
Students explain how one variable affects another in a structured scenario.
Day 1: Matter Does Not Disappear
Students revisit earlier parameter data and consider:
If fish waste or decaying matter enters the system, can it simply vanish?
If we do not remove it, where would it go?
Students are introduced to the concept that waste becomes ammonia.
They are told that ammonia is toxic to fish but naturally converted in established systems.
Bacteria are introduced as living microorganisms that perform chemical conversions within the tank.
Students are shown a simplified sequence:
Organic waste ? Ammonia ? Nitrite ? Nitrate
Without diving into detailed biochemical processes.
The purpose is conceptual clarity, not memorization.
Day 2: The Role of Bacteria and Plants
Students examine where bacteria live in the tank:
On substrate
On tank surfaces
On filter media
On plant roots
They discuss how bacteria rely on oxygen and surface area.
Plants are revisited as organisms that absorb nitrate.
Students are asked:
What would happen if bacteria were absent?
What would happen if plants were absent?
Students begin constructing a flow diagram showing:
Source of waste
Chemical transformation steps
Role of bacteria
Role of plants
Where matter ends up
The purpose is to integrate invisible biological actors into the system model from Segment 1.
Day 3: Building the System Flow Model
Students individually construct a labeled matter flow diagram including:
At least four components
Arrows indicating transformation
Labels for ammonia, nitrite, nitrate
Identification of bacteria as converters
Identification of plants as absorbers
Students then write a brief explanation responding to:
Explain how bacteria contribute to stability in the tank system.
This is not graded as a high stakes assessment. It functions as a process check to ensure conceptual understanding before fish introduction.
DOK Level
DOK 1 for identifying sequence of transformations.
DOK 2 for explaining roles of bacteria and plants.
DOK 3 for constructing and defending a system level matter flow model.
Wastewater treatment facilities rely on bacterial conversion processes to remove harmful compounds from water before release. Aquaculture and aquaponics systems similarly depend on microbial communities to maintain chemical stability. Students are modeling the same biological filtration processes used in professional systems.
Waste dissolves and disappears.
Bacteria are harmful rather than beneficial.
Plants only exist for decoration.
Chemical change requires visible movement.
Stability means nothing is happening.
https://docs.google.com/document/d/1siFIsOAs45CxuUlyJt9dNRdT70eTva14fJMeE1qXHPk/edit?usp=sharing%20
Matter Flow Diagram Submission
Students submit a labeled diagram representing matter movement and transformation in the tank.
Reflection Prompt
Explain in 4 to 6 sentences why bacteria are essential for system stability.
These function as process checkpoints rather than summative evaluations.