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Thermodynamics & Heat
Thermodynamics connects heat, work, and internal energy. You will convert temperature scales, calculate heat and phase changes, compare conduction, convection, and radiation, read PV diagrams, and apply the laws of thermodynamics to engines and entropy.
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What this chapter covers
- Temperature Scales & Thermal Expansion. Temperature questions are mostly conversions and proportional reasoning; always switch to kelvin for anything that involves ratios.
- Heat, Specific Heat & Calorimetry. Heat is energy in transit; the two equations Q = mcΔT and Q = mL, plus 'heat lost = heat gained', solve nearly every problem.
- Conduction, Convection & Radiation. Know which mechanism works in which medium, and know the proportionalities: conduction goes with A/L, radiation with T⁴.
- First Law & PV Diagrams. The first law is an energy ledger, and on a PV diagram work is simply an area.
- Second Law, Heat Engines & Entropy. The second law sets the ceiling on engine efficiency and gives time its direction through entropy.
Key points to know
- K = °C + 273; °F = (9/5)°C + 32
- A 1 K change equals a 1 °C change
- Q = mcΔT within a phase; Q = mL during a phase change
- Temperature is constant while a substance melts or boils
- Conduction: Q/t = kAΔT/L; needs contact
- Convection needs a fluid; radiation needs nothing
- ΔU = Q − W with W done by the system
- Ideal gas: ΔU depends only on ΔT, so isothermal means ΔU = 0
Try a practice question
What is absolute zero on the Celsius scale?
- 0 °C
- −100 °C
- −373 °C
- −273 °C
Show the answer
D. Absolute zero is 0 K, and K = °C + 273, so it is −273 °C. The value −373 °C mixes up the 273 and 373 constants.
Common questions
What does this chapter cover?
Thermodynamics & Heat covers Temperature Scales & Thermal Expansion, Heat, Specific Heat & Calorimetry, Conduction, Convection & Radiation, First Law & PV Diagrams, Second Law, Heat Engines & Entropy.
What should I know first?
K = °C + 273; °F = (9/5)°C + 32 A 1 K change equals a 1 °C change Q = mcΔT within a phase; Q = mL during a phase change
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.