System boundary — Science definition
Defined in 4 courses:
- The chosen limit specifying what is included and which exchanges cross it. (Science 6: Matter, Energy & Earth Systems)
- The chosen limit separating a system from its surroundings. (Science 6: Matter, Energy & Earth Systems)
- The line you draw to decide what is inside the thing you are explaining; stating it stops you crediting one system with the whole chain. (Life Science & Scientific Inquiry)
- The chosen limit separating the objects being studied from their surroundings. (Physical Science: Matter, Forces & Energy)
Where it is taught
- Scientific Inquiry: Questions, Evidence & Explanations — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Variables, Controls & Repeated Trials — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Metric Measurement, Units & Uncertainty — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Tables, Graphs & Patterns in Data — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Models, Systems & Scientific Explanations — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Models, Systems & Scientific Explanations — Inquiry, Measurement & Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- States of Matter & the Particle Model — Matter, Mixtures & Water Properties, Science 6: Matter, Energy & Earth Systems, Grade 6
- Physical Properties & Physical Changes — Matter, Mixtures & Water Properties, Science 6: Matter, Energy & Earth Systems, Grade 6
- Chemical Changes: Evidence & Conservation — Matter, Mixtures & Water Properties, Science 6: Matter, Energy & Earth Systems, Grade 6
- Mixtures, Solutions & Separation — Matter, Mixtures & Water Properties, Science 6: Matter, Energy & Earth Systems, Grade 6
- Water’s Properties: Density, Floating & Surface Effects — Matter, Mixtures & Water Properties, Science 6: Matter, Energy & Earth Systems, Grade 6
- Forms of Energy & Evidence of Transfer — Energy, Heat & Thermal Design, Science 6: Matter, Energy & Earth Systems, Grade 6
- Energy Transformations, Conservation & Dissipation — Energy, Heat & Thermal Design, Science 6: Matter, Energy & Earth Systems, Grade 6
- Heat, Temperature & Thermal Energy — Energy, Heat & Thermal Design, Science 6: Matter, Energy & Earth Systems, Grade 6
- Conduction, Convection & Radiation — Energy, Heat & Thermal Design, Science 6: Matter, Energy & Earth Systems, Grade 6
- Thermal Design: Compare, Improve & Retest — Energy, Heat & Thermal Design, Science 6: Matter, Energy & Earth Systems, Grade 6
- Electric Charge, Attraction & Materials — Electricity, Magnetism & Light, Science 6: Matter, Energy & Earth Systems, Grade 6
- Simple Circuits: Paths, Switches & Energy — Electricity, Magnetism & Light, Science 6: Matter, Energy & Earth Systems, Grade 6
- Magnetic Forces, Fields & Distance — Electricity, Magnetism & Light, Science 6: Matter, Energy & Earth Systems, Grade 6
- Light, Shadows & Reflection — Electricity, Magnetism & Light, Science 6: Matter, Energy & Earth Systems, Grade 6
- Refraction, Color & Transparent Materials — Electricity, Magnetism & Light, Science 6: Matter, Energy & Earth Systems, Grade 6
- Earth’s Spheres & System Interactions — Earth Systems, Plates & Earth Materials, Science 6: Matter, Energy & Earth Systems, Grade 6
- Inside Earth: Layers & Indirect Evidence — Earth Systems, Plates & Earth Materials, Science 6: Matter, Energy & Earth Systems, Grade 6
- Moving Plates, Boundaries & Earth Evidence — Earth Systems, Plates & Earth Materials, Science 6: Matter, Energy & Earth Systems, Grade 6
- Minerals: Properties, Patterns & Identification — Earth Systems, Plates & Earth Materials, Science 6: Matter, Energy & Earth Systems, Grade 6
- Rocks, Weathering & the Rock Cycle — Earth Systems, Plates & Earth Materials, Science 6: Matter, Energy & Earth Systems, Grade 6
- The Water Cycle: Pathways, Stores & Drivers — Water, Air, Weather & Climate, Science 6: Matter, Energy & Earth Systems, Grade 6
- Atmosphere, Clouds & Weather Records — Water, Air, Weather & Climate, Science 6: Matter, Energy & Earth Systems, Grade 6
- Air, Pressure & Uneven Heating — Water, Air, Weather & Climate, Science 6: Matter, Energy & Earth Systems, Grade 6
- Weather & Climate: Time Scales and Comparisons — Water, Air, Weather & Climate, Science 6: Matter, Energy & Earth Systems, Grade 6
- Climate Evidence, Greenhouse Gases & Responses — Water, Air, Weather & Climate, Science 6: Matter, Energy & Earth Systems, Grade 6
- Ecosystems, Habitats & Biomes — Ecosystems, Watersheds & Conservation, Science 6: Matter, Energy & Earth Systems, Grade 6
- Food Chains, Food Webs & Energy Flow — Ecosystems, Watersheds & Conservation, Science 6: Matter, Energy & Earth Systems, Grade 6
- Cycling Matter Through Organisms & Environment — Ecosystems, Watersheds & Conservation, Science 6: Matter, Energy & Earth Systems, Grade 6
- Human Impacts, Conservation & Tradeoffs — Ecosystems, Watersheds & Conservation, Science 6: Matter, Energy & Earth Systems, Grade 6
- Watersheds, Water Quality & Sampling Limits — Ecosystems, Watersheds & Conservation, Science 6: Matter, Energy & Earth Systems, Grade 6
- The Solar System, Gravity & Orbits — Earth, Moon, Sun & Space Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Day, Night & Seasons: Rotation and Tilt — Earth, Moon, Sun & Space Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Moon Phases: Sunlight & Viewing Geometry — Earth, Moon, Sun & Space Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Eclipses & Tides: Alignment with Different Mechanisms — Earth, Moon, Sun & Space Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Space Models: Scale, Evidence & Revision — Earth, Moon, Sun & Space Models, Science 6: Matter, Energy & Earth Systems, Grade 6
- Levels of Organization: Cells to Organ Systems — Body Organization, Transport & Movement, Life Science & Scientific Inquiry, Grade 7
- Atomic Structure — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Physical vs. Chemical Properties — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Density & Floating — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- The Periodic Table — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Materials: Properties, Uses & Impacts — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- States of Matter & Phase Changes — Phases of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Temperature & Thermal Energy — Phases of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Gas Particles, Diffusion & Pressure — Phases of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Evaporation, Condensation & a Wet Cold Cup — Phases of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Heating Curves & Energy During Phase Change — Phases of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Signs of a Chemical Reaction — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Conservation of Mass — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Balancing Chemical Equations — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Endothermic & Exothermic Reactions — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Acids, Bases & pH — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Balanced & Unbalanced Forces — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Interaction Pairs & Force Diagrams — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Gravity & Friction — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Electric & Magnetic Forces — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Pressure & Buoyant Forces — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Speed, Velocity & Acceleration — Motion, Physical Science: Matter, Forces & Energy, Grade 8
- Reading Motion Graphs — Motion, Physical Science: Matter, Forces & Energy, Grade 8
- Newton's Three Laws of Motion — Motion, Physical Science: Matter, Forces & Energy, Grade 8
- Collisions, Deformation & Changes in Motion — Motion, Physical Science: Matter, Forces & Energy, Grade 8
- Designing & Revising a Collision Protector — Motion, Physical Science: Matter, Forces & Energy, Grade 8
- Work: Transferring Energy with a Force — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Levers, Ramps & Pulleys — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Mechanical Advantage — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Efficiency & Improving a Design — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Power: The Rate of Energy Transfer — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Kinetic & Potential Energy — Energy & Heat Transfer, Physical Science: Matter, Forces & Energy, Grade 8
- Energy Transfer & Transformation — Energy & Heat Transfer, Physical Science: Matter, Forces & Energy, Grade 8
- Thermal Energy & Heat Transfer — Energy & Heat Transfer, Physical Science: Matter, Forces & Energy, Grade 8
- Conservation of Energy — Energy & Heat Transfer, Physical Science: Matter, Forces & Energy, Grade 8
- Electricity & Simple Circuits — Energy & Heat Transfer, Physical Science: Matter, Forces & Energy, Grade 8
- Sound Sources, Vibrations & Receivers — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8
- Wave Properties — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8
- Sound Waves — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8
- Light & the Electromagnetic Spectrum — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8
- Waves, Information & a Speaker System — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8
In use
A system boundary is a line you draw to decide what is inside the thing you are explaining and what counts as coming in or going out.
Levels of Organization: Cells to Organ Systems
Questions using system boundary
Problem 1
Which statement correctly uses system boundary in Models, Systems & Scientific Explanations?
- A useful model must reproduce every feature at full size.
- system boundary: The chosen limit separating a system from its surroundings.
- A sealed system cannot exchange energy.
- One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation
system boundary: The chosen limit separating a system from its surroundings.
The chosen limit separating a system from its surroundings. The record is consistent with water remaining inside the sealed system while energy transfers to cooler surroundings. The 10 °C drop is not ten joules; calculating energy would require additional information. Constant measured mass does not mean every particle is motionless or that the container blocks energy.
Problem 2
An illustrative rolling system starts with 80 J mechanical energy. Later it has 55 J mechanical energy, 20 J additional thermal energy in the system and 5 J transferred to surroundings. Write a complete energy account and explain the system boundary. Distinguish reduced mechanical energy from reduced total accounted energy.
Answer and explanation
55+20+5=80 J accounts for the initial amount. Mechanical energy fell by 25 J, but energy is redistributed within and across the boundary. A closed boundary for matter can still exchange energy; an isolated ideal system exchanges neither. State the boundary and include transfers before claiming energy disappeared.
55+20+5=80 J accounts for the initial amount. Mechanical energy fell by 25 J, but energy is redistributed within and across the boundary. A closed boundary for matter can still exchange energy; an isolated ideal system exchanges neither. State the boundary and include transfers before claiming energy disappeared.
Response criteria
- Use the supplied conditions and relevant evidence.
- Explain the scientific mechanism or calculation.
- State a meaningful limitation or testable next step.
Taught alongside
- observation
- inference
- evidence
- uncertainty
- independent variable
- dependent variable
- unit
- resolution
- mean
- pattern
- model
- particle model
- evaporation
- physical property