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Lesson Notes

වියාචනය (Disclaimer)

Idasara Academy ඉගෙනුම් සම්පත් නිර්මාණය කර ඇත්තේ සිසුන්ට මගපෙන්වීම, පුහුණුව සහ අධ්‍යයන උපායමාර්ග ලබාදී සහයෝගය දැක්වීමටය.

කෙසේ වෙතත්, සියලුම විභාග සහ නිල අවශ්‍යතා සඳහා, සිසුන් අනිවාර්යයෙන්ම ශ්‍රී ලංකා අධ්‍යාපන අමාත්‍යාංශයේ, අධ්‍යාපන ප්‍රකාශන දෙපාර්තමේන්තුව විසින් ප්‍රකාශයට පත් කරන ලද නිල පෙළපොත් සහ සම්පත් පරිශීලනය කළ යුතුය.

ජාතික විභාග සඳහා අන්තර්ගතයේ නිල බලය ලත් මූලාශ්‍රය වනුයේ රජය විසින් නිකුත් කරනු ලබන මෙම ප්‍රකාශනයි.

Unit 4: Thermal Physics

Grade

12

Lesson 4.1 – Temperature & Thermometers 


Foundation (Q1–5)

  1. Define temperature.

  2. State two types of thermometers.

  3. What are the fixed points used to calibrate thermometers?

  4. Convert 30°C to Kelvin.

  5. Define thermometric property.


Intermediate (Q6–10)

  1. Explain why gas thermometers are more accurate.

  2. Distinguish between Celsius and Kelvin scale.

  3. What is meant by linearity in thermometers?

  4. A thermometer reads 70°C. Express this in Kelvin.

  5. Describe how a thermocouple thermometer works.


Advanced (Q11–15)

  1. Explain why ideal gas thermometer is considered a standard thermometer.

  2. Discuss limitations of mercury thermometers.

  3. Analyse temperature–resistance relationship in resistance thermometers.

  4. Compare advantages of thermocouple vs thermistor.

  5. Explain why absolute zero cannot be reached in practice.



Lesson 4.2 – Thermal Expansion 


Foundation (Q1–5)

  1. Define thermal expansion.

  2. State coefficient of linear expansion.

  3. Name two practical examples of expansion.

  4. Write formula for linear expansion.

  5. What is anomalous expansion of water?


Intermediate (Q6–10)

  1. A rod of length 2 m expands by 0.4 mm when heated. Find α.

  2. Explain why bridges have expansion gaps.

  3. Distinguish linear, area, and volume expansion.

  4. Describe behaviour of water between 0°C and 4°C.

  5. A liquid expands by 5 cm³ when heated. What is its apparent expansion?


Advanced (Q11–15)

  1. Derive relation γ = 3α.

  2. Explain why bimetallic strip bends when heated.

  3. Analyse effect of temperature on density using expansion formulas.

  4. Determine rise in mercury in thermometer given bulb dimensions.

  5. Explain real vs apparent expansion of liquids.



Lesson 4.3 – Gas Laws & Ideal Gas Equation 


Foundation (Q1–5)

  1. State Boyle’s law.

  2. State Charles’s law.

  3. Define absolute zero.

  4. What is pressure?

  5. Write the combined gas equation.


Intermediate (Q6–10)

  1. A gas at 2 L volume is compressed to 1 L at constant temperature. What happens to pressure?

  2. Convert 25°C to Kelvin.

  3. Explain why balloon expands when heated.

  4. Apply PV = nRT to find volume of 2 moles at STP.

  5. Distinguish isothermal and isobaric processes.


Advanced (Q11–15)

  1. Derive PV = nRT using gas laws.

  2. Explain assumptions of kinetic theory in ideal gas equation.

  3. Solve multi-step gas problem involving temperature & pressure changes.

  4. Analyse deviations from ideal behaviour.

  5. Interpret PV–T graphs for different processes.



Lesson 4.4 – Kinetic Theory of Gases 


Foundation (Q1–5)

  1. What is kinetic theory?

  2. State two assumptions of kinetic theory.

  3. Define RMS speed.

  4. What is meant by elastic collision?

  5. Write formula for average kinetic energy.


Intermediate (Q6–10)

  1. Explain relation between temperature and molecular kinetic energy.

  2. Discuss pressure in terms of molecular collisions.

  3. Explain difference between heat and internal energy.

  4. State relation between RMS speed and temperature.

  5. Describe Brownian motion.


Advanced (Q11–15)

  1. Derive pressure equation from kinetic theory.

  2. A gas temperature doubles. What happens to RMS speed?

  3. Analyse molecular speed distribution graph.

  4. Discuss real gas deviations using kinetic theory.

  5. Relate kinetic theory to diffusion.



Lesson 4.5 – Specific Heat Capacity & Cooling 


Foundation (Q1–5)

  1. Define specific heat capacity.

  2. Write formula for heat absorbed.

  3. What is cooling rate?

  4. State Newton’s law of cooling.

  5. What is thermal capacity?


Intermediate (Q6–10)

  1. A body of mass 2 kg requires 2000 J to rise 10°C. Find SHC.

  2. Explain difference between high and low SHC materials.

  3. Describe applications of SHC in daily life.

  4. Explain why black objects cool faster.

  5. Discuss factors affecting cooling rate.


Advanced (Q11–15)

  1. Derive Newton’s law of cooling.

  2. Solve calorimetry problem involving mixing of substances.

  3. Analyse cooling curve for anomalies.

  4. Compare SHC of solids, liquids, gases.

  5. Explain why SHC increases at constant pressure.



Lesson 4.6 – Latent Heat & Phase Change 


Foundation (Q1–5)

  1. Define latent heat.

  2. State two types of latent heat.

  3. What happens to temperature during melting?

  4. Write formula Q = mL.

  5. Define boiling point.


Intermediate (Q6–10)

  1. Explain plateau region in heating curve.

  2. Why does sweating cool your body?

  3. A 0.5 kg ice melts at 0°C. Calculate heat absorbed.

  4. Describe molecular behaviour during phase change.

  5. Distinguish evaporation vs boiling.


Advanced (Q11–15)

  1. Analyse heating curve from ice to steam.

  2. Derive relation between latent heat and intermolecular forces.

  3. Solve multi-step calorimetry question involving phase changes.

  4. Explain why boiling point changes with altitude.

  5. Discuss energy distribution during vaporisation.



Lesson 4.7 – Humidity & Vapour Pressure 


Foundation (Q1–5)

  1. Define humidity.

  2. What is saturated vapour pressure?

  3. Define dew point.

  4. What is relative humidity?

  5. Name one instrument used to measure humidity.


Intermediate (Q6–10)

  1. Explain why clothes dry faster on warm days.

  2. Describe relationship between temperature and vapour pressure.

  3. Calculate RH given actual = 20 Pa & saturated = 25 Pa.

  4. Explain condensation.

  5. How does humidity affect comfort level?


Advanced (Q11–15)

  1. Analyse humidity data and predict weather changes.

  2. Explain fog formation using vapour pressure.

  3. Solve multi-step RH calculation.

  4. Discuss limitations of psychrometer.

  5. Compare vapour pressure of different liquids using molecular forces.



Lesson 4.8 – Thermodynamic Processes 


Foundation (Q1–5)

  1. Define isothermal process.

  2. What is adiabatic process?

  3. Define isochoric process.

  4. Define isobaric process.

  5. State the first law of thermodynamics.


Intermediate (Q6–10)

  1. Compare isothermal & adiabatic processes.

  2. Explain why no heat enters gas during adiabatic expansion.

  3. Sketch PV graph for isothermal process.

  4. Sketch PV graph for adiabatic process.

  5. Solve simple internal energy change problem.


Advanced (Q11–15)

  1. Derive PV^γ = constant for adiabatic process.

  2. Analyse multi-process cycle on PV diagram.

  3. Solve work done in isothermal expansion.

  4. Explain thermodynamic efficiency.

  5. Compare heat transfer in different processes quantitatively.



Lesson 4.9 – Heat Transfer 


Foundation (Q1–5)

  1. Define conduction.

  2. Define convection.

  3. Define radiation.

  4. Give one conductor & one insulator.

  5. What is thermal conductivity?


Intermediate (Q6–10)

  1. Explain why black surfaces absorb more heat.

  2. Describe natural vs forced convection.

  3. State conduction equation: Q/t = kAΔT/L.

  4. Explain greenhouse effect.

  5. Discuss ways to reduce heat loss in homes.


Advanced (Q11–15)

  1. Derive conduction equation.

  2. Solve heat-loss problem through walls.

  3. Analyse efficiency of heat exchanger.

  4. Explain radiation spectrum and Stefan–Boltzmann law qualitatively.

  5. Compare convection in liquids vs gases.

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