QUICK REVIEW
Quick Review — First Law of Thermodynamics — Foundational
Refresh the essential ideas and relationships for First Law of Thermodynamics in just a few minutes.
TIME
5–10 minutes
BEST FOR
A rapid refresh
FINISH WITH
Key ideas refreshed
After this quick review, you'll be able to...
recall the essential ideas and decide what to review next.
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Course Alignment
This Physics Sensei Unit Review is an independent learning resource. Use it to reinforce key concepts, prepare for homework, or review before a quiz or exam.
RESOURCE: Physics Sensei Unit Review | UNIT ID: THM-U08 | TOPIC: First Law of Thermodynamics | COURSE LEVEL: Foundational
BEST USED ✓ After learning the unit ✓ Before starting homework ✓ Before a quiz or exam
Your Review Plan
Complete these four stages to quickly refresh the essential ideas and confirm you're ready to continue.
4 Stages • Approximately 5–10 minutes.
Quick Recall
Let's quickly refresh what you already know. These short recall activities will help you bring the most important ideas back to mind before reviewing them.
QUICK RECALL
Recall Activity
Complete the three statements from memory before revealing the answer.
Energy-transfer signs: Use the convention W = work done by the system. If 200 J of heat enters a gas and the gas does 50 J of work, is Q positive or negative? Is W positive or negative?
Reveal Answers
Q is positive and W is positive.
Why it works: Energy entering as heat makes Q > 0; expansion work done by the system makes W > 0.
Ready to refresh the essentials?
Great! Now let's review the most important ideas you'll want to remember.
Essential Idea
Take one last look at the most important concept from this unit. If you remember this idea, the rest will come back much more easily.
ESSENTIAL IDEA
The First Law
Energy conservation for a thermodynamic system is ΔU = Q - W, where W is work done by the system. Heat added to the system is positive Q; heat leaving is negative Q.
ΔU = Q − W
Example: If Q = 500 J and W = 120 J, then ΔU = 380 J.
Sensei note: Choose and state one sign convention before calculating; most sign mistakes come from switching conventions.
Ready to check your memory?
You've refreshed the essential idea. Now see how much you remember before moving on. Need a quick reminder?
Confidence Check
You've refreshed the essential ideas. Now answer this quick confidence check to confirm you're ready to move on.
CONFIDENCE CHECK
Sign of compression
Answer all three without notes.
Solve using the first law and the stated sign convention. An adiabatic compression has Q = 0 and W = -90 J. Find ΔU.
Reveal Answers
ΔU = 90 J.
Why it works: ΔU = 0 - (-90 J).
Ready for your next step?
Great work! You've refreshed the essential ideas. Now choose the resource that best matches what you'd like to do next. Need a quick reminder?
Next Step
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