Heat & Thermodynamics

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Q1. According to the first law of thermodynamics, what happens to the internal energy of a system when heat is added and work is done by the system?

Solution:

The first law states ΔU = Q - W. If heat Q is added and work W is done by the system, the internal energy decreases.

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Q2. What is the root mean square speed of gas molecules at a temperature of 300 K for a gas with a molar mass of 0.029 kg/mol?

Solution:

Using the formula v_rms = sqrt(3RT/M), where R = 8.314 J/(mol·K), T = 300 K, and M = 0.029 kg/mol, we find v_rms ≈ 400 m/s.

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Q3. What is entropy a measure of?

Solution:

Entropy is a measure of disorder or randomness in a system, indicating the number of ways a system can be arranged.

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Q4. In a heat engine, what is the purpose of the heat sink?

Solution:

The heat sink in a heat engine is used to release excess heat to the environment, allowing the engine to operate efficiently.

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Q5. Which of the following is NOT a thermodynamic process?

Solution:

All listed processes are thermodynamic processes; however, 'Isobaric' is often confused with 'Isothermal' but is indeed a valid process.

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Q6. What is the primary mechanism of heat transfer in fluids?

Solution:

The primary mechanism of heat transfer in fluids is convection.

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Q7. What happens to the volume of a gas when it is heated at constant pressure?

Solution:

According to Charles's Law, the volume of a gas increases when it is heated at constant pressure.

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Q8. If the volume of a gas is halved at constant temperature, what happens to the pressure?

Solution:

According to Boyle's law, pressure is inversely proportional to volume at constant temperature. If the volume is halved, the pressure doubles.

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Q9. If the entropy of a system increases, what can be inferred about the system?

Solution:

An increase in entropy indicates that the system is becoming more disordered.

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Q10. In an ideal gas, what is the relationship between pressure and temperature at constant volume?

Solution:

According to Gay-Lussac's Law, pressure is directly proportional to temperature at constant volume.