Energy Systems & ConservationANSWER KEY
Name: Period: Date:
1.Only thermal energy transfers; 'cold' is absence of thermal energy
2.Temperature measures average kinetic energy; heat is energy transfer
3.Metals conduct heat faster, so they feel cold by drawing heat from your hand
4.Energy is conserved; it transforms between forms but total amount stays constant
[!] STUDY GUIDE: Big Ideas Use to answer form questions!
1.Energy systems have inputs, outputs, and losses. Energy enters a system, does useful work, and some is "lost" to thermal energy (friction, heat).
2.Efficiency = useful output / total input. No machine is 100% efficient because some energy always becomes thermal energy.
3.Perpetual motion is IMPOSSIBLE. Since energy is always lost to thermal energy, machines can't run forever without adding energy.
Energy Input (100J) -> SYSTEM -> Useful Output (70J) + Lost Heat (30J)
EFFICIENCY = 70J / 100J = 70% (Energy is conserved: 70 + 30 = 100!)
[#] KEY TERMS Define in YOUR words
System
Set of interacting parts
Efficiency
% of useful output vs input
Energy Input
Energy put into a system
Energy Loss
Energy converted to heat/sound
[?] THE PHENOMENON Write BEFORE Hook form
Why can't perpetual motion machines work?
People have tried for centuries to build machines that run forever without fuel. Why do they always fail?
Your initial thinking:
[>] AFTER HOOK FORM Reflect, then continue +2 pts
I learned that...
Station 1 — Energy System Investigation
Energy input =
Where energy goes (useful + lost):
Key insight:
Station 2 — Efficiency Analysis
Machine A efficiency =
Machine B efficiency =
Key insight:
[/] DAY 1 EXIT TICKET Complete before leaving +5 pts
Q1:
A car engine is 25% efficient. If you put in 100J of fuel energy, how much moves the car? Where does the rest go?
Q2:
Why is it impossible for any machine to be 100% efficient?
Confidence:
NGSS: MS-PS3-5 Page 1 of 2 | Day 1 v3.5
Energy Systems & Conservation (continued)ANSWER KEY
Name:
[=] Day 2 start
Station 3 — Design an Efficient System
My system converts energy from ___ to ___:
Ways I reduced energy loss:
My design's efficiency =
Key insight:
[+] MAKING CONNECTIONS Use for Exit Ticket!
How do collision energy losses (W6) relate to efficiency (W7)?
Why can't perpetual motion machines work? Explain using energy conservation.
[/] DAY 2 EXIT TICKET Final check before Science Circle +5 pts
Q1 (NEW):
Someone shows you a "perpetual motion machine." What scientific law tells you it must be fake?
Q2 (SPIRAL-W6):
In an inelastic collision, kinetic energy decreases. Does this violate energy conservation? Explain.
Q3 (INTEGRATION):
Trace the energy in an electric car: from the battery, through the motor, to the wheels, to heat. Why isn't it 100% efficient?
CHECK TEST YOUR THINKING Rate each: FALSE ← 1–2–3–4–5 → TRUE
1. Cold can transfer from one object to another
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2. Temperature and heat are the same thing
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3. Metals are naturally colder than other materials
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4. Energy can disappear or be used up
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5. Only thermal energy transfers; 'cold' is absence of thermal energy
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Pick any TWO statements — especially any you rated 2, 3, or 4. Justify your rating with evidence:
Statement #___ — I rated it ___ because:
Statement #___ — I rated it ___ because:
[O] SCIENCE CIRCLE ~15 min | End of week +3 pts
[!] My "Aha!" Moment
[?] My Remaining Question
Discussion Protocol: Share ahas, listen actively, record class discoveries.
CLASS DISCOVERIES
1.
2.
[X] We used to think:
[OK] Now we understand:
[*] Something challenging I tried:
NGSS: MS-PS3-5 Page 2 of 2 | Day 2 v3.5