System Boundaries Slides Lesson 1: Systems
SYSTEM
BOUNDARIES
Where does the energy stop and the world begin?
01
The Morning Coffee Dilemma
The Ceramic Mug
Your coffee is cold in 20 minutes. Why?
The Vacuum Thermos
Your coffee is hot 6 hours later. How?
"Is it possible to create a box that nothing—not even heat—can enter or leave?"
What is a System?
The System
The specific part of the universe we are studying (like the water in a cup).
The Surroundings
Everything else outside the system (the air, the table, the room).
The Boundary
The "wall" that separates the system from its surroundings.
SYSTEM TYPES
OPEN
Energy can enter/leave
Matter can enter/leave
CLOSED
Energy can enter/leave
Matter CANNOT leave
ISOLATED
Energy CANNOT leave
Matter CANNOT leave
The Reality Check
In the real world, a "Perfectly Isolated System" is impossible to build. Energy always finds a way out (or in).
"So why do scientists use the idea of a closed system if it doesn't really exist?"
System Boundaries Worksheet SYSTEM BOUNDARIES
Energy Investigation 01.1
Name:
Date:
Part 1: Defining the Limits
Match the thermodynamic term to its correct definition.
1
System: Everything else outside of the area being studied.
2
Surroundings: The specific collection of matter or region of space under investigation.
3
Boundary: The interface (real or imaginary) that separates the study area from everything else.
Part 2: The Coffee Experiment
Imagine you have two containers of hot coffee: an Open Ceramic Mug and a Sealed Thermos . In the diagrams below, label the System, Surroundings, and Boundary.
MUG A
Open System
MUG B
Closed System
1. In Mug A, what two things can pass across the boundary into the surroundings?
2. In Mug B, which of those two things is now "trapped" by the boundary?
Part 3: The Isolated Challenge
"An isolated system is one where neither matter nor energy can cross the boundary."
Think about a Thermos. It keeps soup hot for hours, but eventually, it still gets cold. Why?
Predict: If you left a thermos in space (a perfect vacuum) for 1 million years, would the coffee eventually get cold? Why or why not?
Evaluate: Why do scientists use the "Closed System" model if they know some energy always leaks out? How does this model help them do better science?
Heat Hunters Sequence
© 2026 Thermodynamic Investigations
System Boundaries Teacher Guide Teacher Guide
LESSON 1: SYSTEM BOUNDARIES
Objective
Students will be able to define the boundaries of a thermodynamic system and differentiate between open, closed, and isolated systems to explain energy conservation challenges.
Essential Question
"Is it possible to create a box that nothing—not even heat—can enter or leave?"
Prep Checklist
1 Ceramic Mug
1 Insulated Thermos
Hot water / Thermometers
Worksheet copies
01
The Hook (10 mins)
Present the mug and the thermos. Ask students: "Which one will protect my coffee from the laws of physics the longest?" Discuss how the physical boundary of the thermos is designed to block energy transfer.
Key Question: "If I put the thermos in a vacuum, would it keep things hot forever?" (No, radiation and leakage through the seal still occur).
02
Direct Instruction (15 mins)
Use the slides to define System (what we care about), Surroundings (everything else), and Boundary (the wall). Emphasize that matter is particles, and energy is (primarily) heat in this context.
Type Matter Exchange? Energy Exchange? Open YES YES Closed NO YES Isolated NO NO
03
Workshop & Practice (25 mins)
Students complete the worksheet. Circulate and check for the "Isolated System" misconception : students often think a thermos is an isolated system. Remind them that isolated systems are theoretical models; in reality, all systems "leak" energy eventually.
Misconception Alert
Students may think "Closed" means "completely cut off." Clarify that a closed system (like a sealed balloon or a closed jar) still allows heat to pass through its walls, even if the air inside cannot get out.
Energy Flow Lab Sheet ENERGY FLOW TRACKERS
Energy Investigation 02.1
Team:
Date:
Mission Objective
Can we track every Joule of energy? You will mix hot and cold water and use the conservation of energy law to see if the energy "lost" by the hot water equals the energy "gained" by the cold water.
The Energy Tracker Formula
\[ Q = m \cdot c \cdot \Delta T \]
Energy (J) = Mass (g) × 4.18 × Temp Change (°C)
Data Log
Variable Cold Water (System A) Hot Water (System B) Mass (m) in grams Initial Temp (Ti) in °C Final Mix Temp (Tf) in °C Temp Change (ΔT) Tf - Ti
Tracking the Joules
1. Energy Gained by Cold Water ($Q_{cold}$)
2. Energy Lost by Hot Water ($Q_{hot}$)
The "Missing" Energy
Subtract: $Q_{hot} - Q_{cold} = $ ____________________ Joules
Where did the "missing" energy go? Explain why $Q_{hot}$ is usually larger than $Q_{cold}$ in a real classroom setting.
End of Lab 02.1 - Submit for analysis
Energy Flow Slides Lesson 2: Energy Flow
TRACKING
JOULES
The math behind the heat.
The Golden Rule of Energy
"Energy cannot be created or destroyed.
HOT WATER
Loses Energy
COLD WATER
Gains Energy
How do we measure heat?
\[ Q = mc\Delta T \]
Q: Thermal Energy (Joules)
m: Mass (Grams)
c: Specific Heat (4.18 for Water)
ΔT: Temperature Change (°C)
Think of it like money:
Energy is the currency. We are the accountants tracking the bank transfer between the hot cup and the cold cup.
The Challenge:
"The bank has a leak." Some energy always escapes to the surroundings (the cup, the air).
THE PHANTOM LOSS
If the hot water loses 1000 Joules, but the cold water only gains 800 Joules... where did the 200 Joules go?
The Cup
The plastic or glass gets warmer.
The Air
Heat escapes from the top.
The Sensor
The thermometer takes some heat.
Energy Flow Answer Key Teacher Resource
Lab Answer Key & Facilitation: Energy Flow
Typical Data Results
Note: Values will vary based on water volume and starting temps, but the patterns should remain consistent.
Pattern 1: The Final Temperature
If using equal masses (e.g., 100g each), $T_f$ will be the exact average if the system were isolated . In class, it will be slightly lower than the average because heat is lost to the cup.
Pattern 2: Joule Discrepancy
$Q_{hot}$ should always be greater than $Q_{cold}$ in a real-world lab. Usually, a 10-20% difference is expected.
Analysis Question Guide
Q: Where did the "missing" energy go?
Expected Answer: The energy was transferred to the surroundings . This includes the plastic/Styrofoam cup, the thermometer itself, and the air above the water.
Q: Does this experiment disprove the Law of Conservation of Energy?
Expected Answer: No. It simply shows that our system was not closed . Energy still exists; it's just no longer in the water.
Sample Calculation for Verification
If 100g of 80°C water is mixed with 100g of 20°C water...
Cold Water Side
$m = 100g, \Delta T = 25°C$
$Q = 100 \cdot 4.18 \cdot 25$
$Q = 10,450 J$
Hot Water Side
$m = 100g, \Delta T = 30°C$
$Q = 100 \cdot 4.18 \cdot 30$
$Q = 12,540 J$
The "Missing" 2,090 Joules went into the cup and air.
Equilibrium Quest Guide EQUILIBRIUM QUEST
Energy Investigation 03.1
Observer:
The Balancing Act
In this simulation, you will mix objects of different temperatures and masses. Your goal: Predict and observe the exact moment when the "energy swapping" stops.
1
Trial: Identical Masses
Set Object A to 80°C (100g) and Object B to 20°C (100g). Press "Run".
Prediction
What will the final temperature be?
Observations
2
Trial: Mass Imbalance
Set Object A to 80°C (400g ) and Object B to 20°C (100g ). Press "Run".
Prediction
Will the final temp be closer to 80 or 20? Why?
Observations
Simulation Analysis
1. Define "Thermal Equilibrium" based on what you saw in the simulation graphs.
2. Did heat ever flow from the COLD object to the HOT object? Support your answer with evidence.
Equilibrium Slides Lesson 3: Equilibrium
THERMAL
BALANCE
When does the energy swap stop?
The Particle Perspective
HOT PARTICLES
Fast & Chaotic
High Kinetic Energy
COLD PARTICLES
Slow & Steady
Low Kinetic Energy
The Collision
When they touch, fast particles slam into slow ones.
They transfer their speed (energy) until everyone is moving at the same average speed.
EQUILIBRIUM
The state where two objects in physical contact have the same temperature .
"Net heat flow becomes zero. The exchange doesn't stop, but the temperatures no longer change."
Equilibrium in the Wild
Melting Ice
The ice reaches equilibrium with the warm air in the room.
Cooling Bath
The hot water reaches equilibrium with the bathroom temperature.
Everything wants to be room temp.
Equilibrium Exit Ticket EQ
Equilibrium Exit Ticket
Investigation 03.Z
Question 1
You place a hot metal spoon (90°C) into a cold glass of water (5°C). After 10 minutes, they reach thermal equilibrium . Which of the following must be true?
The spoon is still hotter than the water.
The water and the spoon are the same temperature.
The energy has been destroyed during the cooling process.
Question 2
Draw arrows in the diagram below to show the direction of heat flow when a hot object meets a cold object.
HOT
Flow?
COLD
Question 3
"If I have a massive swimming pool at 20°C and I drop in a small red-hot penny, why doesn't the pool's temperature change significantly?"
Verified Logic
Heat Hunters 03
Friction Heat Lab Sheet FRICTION FIRE LAB
Energy Investigation 04.1
Investigator:
The Mechanical Spark
Energy doesn't just disappear when things stop moving—it changes form. In this lab, you will generate thermal energy using only your muscles and friction.
"Can you boil water just by stirring it really, really fast?"
Inventory
- 1 Metal Coat Hanger
- 1 Block of Wood
- 1 Sheet of Sandpaper
- Infrared Thermometer
01
Task 1: The Bend
Hold the coat hanger and bend it back and forth rapidly 20 times at the same spot. CAUTION: It will be hot! Immediately measure the temperature of the bend.
Start Temp
_______ °C
After 20 Bends
_______ °C
Total Change
_______ °C
02
Task 2: The Rub
Vigorously sand the wooden block with the sandpaper for 30 seconds. Measure the temperature of the wood surface and the sandpaper.
Wood Surface Temp:
_______ °C
Sandpaper Temp:
_______ °C
Energy Forensic Report
1. Transformation Path: Trace the energy from your lunch to the heat in the metal hanger.
Chemical (Food) → Kinetic (Arm) → ____________ → Thermal (Hanger)
2. Why did the temperature go up? What happened to the atoms in the metal as you bent it?
Transformation Slides Lesson 4: Transformation
ENERGY
MORPHING
Energy never leaves, it just changes clothes.
Mechanical → Thermal
KINETIC ENERGY
The energy of moving objects. A spinning drill, a sliding block, a moving arm.
THERMAL ENERGY
The internal energy of particles. The "jiggling" of atoms. When things stop moving, where does the kinetic energy go?
FRICTION
"The Bridge Between Forms"
Why does it get hot?
At the microscopic level, even smooth surfaces look like jagged mountain ranges.
When surfaces slide, these "peaks" crash into each other. This microscopic collision makes the atoms vibrate faster.
Vibration = Heat
SURFACE CONTACT INTERFACE
THE STIRRING CHALLENGE
James Joule (the guy we named Joules after) proved you can boil water just by stirring it.
THE PROBLEM
You need to stir it for days at high speed to see a real change.
THE PHYSICS
The friction between the spoon and the water molecules creates thermal energy.
THE RESULT
100% of the mechanical energy eventually becomes thermal energy.
Friction Lab Teacher Prep Teacher Prep
Lesson 4: Friction Fire Lab Setup
Station Requirements
Coat Hangers
Standard metal hangers. Cut them into 12-inch straight sections if possible for easier handling, or leave whole for more leverage.
Abrasives
Coarse sandpaper (60-80 grit) works best for rapid heat generation. Scrap wood blocks should be soft (pine or cedar).
Measurement
Infrared (IR) thermometers are highly recommended for this lab to capture the temperature of the surface instantly without losing heat to a probe.
Safety Briefing
Students will generate enough heat to cause minor burns if they touch the metal or wood immediately after friction.
Use IR thermometers instead of fingers to "check" for heat.
Ensure students are wearing safety goggles (especially during sanding).
Remind students not to bend the metal to the point of breaking/snapping.
The "Aha!" Moment
The goal is to connect the kinetic motion (mechanical energy) directly to the temperature rise . If a student says "I'm tired," respond with: "That's because you just converted your chemical energy into heat!"
What Students Should Find
Metal Hanger
Bending causes internal friction between atoms. Expect a 10-20°C jump in temp in just 30 seconds.
Sandpaper/Wood
The sandpaper usually gets hotter than the wood because it has less mass to heat up.
Missing Energy
Some energy will go into sound (the scuffing noise) and microscopic vibration of the air.
Body Engine Slides Lesson 5: Living Systems
THE BODY
ENGINE
Physics doesn't stop at the skin.
The Biological Closed System
INPUT
Chemical Energy (Food)
OUTPUT
Mechanical Work + HEAT
Your body is only about 25% efficient.
75% of the energy from your food is "lost" as thermal energy.
Cooling the Engine
When you exercise, your "engine" creates a massive amount of waste heat.
Evaporative Cooling
Sweat absorbs thermal energy from your skin. When it evaporates, it takes that energy with it into the surroundings.
BOUNDARY CONTROL
Sweating is how your system maintains equilibrium with the environment.
THE PHYSICS OF LIFE
Every breath you take and every move you make is just the Law of Conservation of Energy in action.
Homeostasis
A biological state of thermal equilibrium.
98.6°F
Your system's target operating temperature.
Body Engine Case Study BODY ENGINE CASE STUDY
Energy Investigation 05.1
Researcher:
The Marathon Problem
During a marathon, a runner's muscles generate a massive amount of kinetic energy. However, only 20-25% of the energy from their food actually goes into moving their legs. The rest is converted into waste heat . If the runner didn't have a way to export this energy to the surroundings, their core temperature would rise by 1°C every 5 minutes. Within 45 minutes, they would reach a lethal temperature.
To survive, the runner's body opens a "boundary valve" (pores) to release sweat. As the sweat evaporates, it absorbs large amounts of thermal energy from the skin and carries it away into the air. This is an application of Thermal Equilibrium : the body is desperately trying to stay at 37°C while the environment and internal metabolism are pushing it higher.
Part 1: The Energy Map
In the box below, create a System Diagram for the runner. Label the Boundary (skin), the Surroundings (air/track), and show the flow of Energy In (Food) and Energy Out (Heat/Work).
Part 2: Bio-Physics Analysis
1. Why is the human body considered an Open System rather than a Closed System?
2. If a runner is in a very humid environment, sweat doesn't evaporate as easily. How does this affect their ability to reach thermal equilibrium? Use physics terms.
Biological Thermodynamics
Final Reflection Prompt Sequence Conclusion
THE FINAL
VERDICT
Essential Question
"Does heat energy ever truly disappear, or does it just move somewhere else?"
Reflect on your investigations into coffee mugs, water mixing, friction, and the human body. Write a comprehensive response using at least three of the following terms: System, Conservation, Transformation, Equilibrium, Surroundings.
Physics Laws
Entropy
End of Sequence: Investigating Energy Conservation and Equilibrium
