Fundamental Concepts in Thermodynamics and Fluid Properties

1. Specific Volume and Critical Conditions

Statement: The specific volume of a gas is the volume that would occupy 1 mole of that gas at its critical temperature and pressure. (False)

Correction and Explanation:

This statement is false. The critical volume is the volume occupied by one mole of a substance at its critical point. Specific volume, by definition, is the volume per unit mass of a substance. The original statement incorrectly defines specific volume in terms of molar volume at critical conditions.

2. Adiabatic Processes and Heat Transfer

Statement: When there is heat loss to the environment, a process cannot be adiabatic. (True)

Explanation:

An adiabatic process is fundamentally defined by the absence of heat transfer (Q=0) to or from the surroundings. Therefore, if heat is lost to the environment, the process cannot be considered adiabatic.

3. Understanding Gauge Pressure

Statement: Gauge pressure is defined as the difference between internal (absolute) pressure and atmospheric pressure. (True)

Explanation:

This statement is true. Gauge pressure measures the pressure relative to the surrounding atmospheric pressure. It is calculated as: Gauge Pressure = Absolute Pressure - Atmospheric Pressure.

4. Calculating Gauge Pressure

Statement: For an atmospheric pressure of 1.1 atm, if the barometric pressure reads 1.8 atm, then the gauge pressure is 2.9 atm. (False)

Correction and Explanation:

This statement is false. Gauge pressure is the difference between the absolute (barometric) pressure and the atmospheric pressure. Therefore, the correct calculation is: 1.8 atm - 1.1 atm = 0.7 atm, not 2.9 atm.

5. Temperature Scales: Celsius and Kelvin

Statement: If the temperature of a body increases by 10°C, its temperature on the Kelvin scale increases to 283 K. (False)

Correction and Explanation:

This statement is false. An increase of 10°C is equivalent to an increase of 10 K. The value 283 K corresponds to 10°C (since 0°C = 273.15 K), but an increase of 10°C does not mean the temperature becomes 283 K unless it started at 0°C.

6. Principle of Corresponding States

Statement: Any substance has the same reduced volume at the same reduced temperature and reduced pressure. (True)

Explanation:

This principle, known as the Principle of Corresponding States, suggests that all fluids, when compared at the same reduced temperature and reduced pressure, have approximately the same reduced volume. This is a useful generalization in thermodynamics.

7. Temperature and Atomic Motion

Statement: Temperature measures the degree of thermal motion of atoms in a body. (True)

Explanation:

Temperature is a fundamental thermodynamic property that is a measure of the average kinetic energy of the particles (atoms or molecules) within a system. Higher temperature implies greater thermal motion.

8. Phase Diagrams and Curves

Statement: A phase diagram showing the equilibrium between liquid and vapor phases includes the sublimation curve. (False)

Correction and Explanation:

This statement is false. A phase diagram between the liquid and vapor phases features the vaporization curve (also known as the boiling or condensation curve). The sublimation curve represents the equilibrium between the solid and gas phases.

9. Thermal Reservoirs and Heat Capacity

Statement: Heat receptors are bodies that can absorb or release unlimited amounts of heat without significant temperature changes. (False)

Correction and Explanation:

This statement is false. Such bodies are accurately known as thermal reservoirs or heat sinks/sources, not 'heat receptors'. They are characterized by their very large thermal capacity, allowing them to exchange heat without a noticeable change in their own temperature.

10. Defining the British Thermal Unit (BTU)

Statement: A British Thermal Unit (BTU) is the amount of heat that must be added to one pound of liquid water at a pressure of 14.69 PSI to raise its temperature by 1 K. (False)

Correction and Explanation:

This statement is false. A BTU is defined as the amount of heat required to raise the temperature of one pound of liquid water by 1°F (Fahrenheit), not 1 K (Kelvin). The pressure of 14.69 PSI is standard atmospheric pressure.

11. Gas Condensation and Critical Temperature

Statement: A gas is a state in which, upon increasing pressure, it cannot condense without varying the temperature.

Explanation:

This statement accurately describes a gas above its critical temperature. Below the critical temperature, a gas can be condensed into a liquid by increasing pressure alone. However, above the critical temperature, it cannot be liquefied by pressure alone, regardless of how much pressure is applied; the temperature must also be lowered.

12. Understanding Critical Pressure

Statement: Critical pressure corresponds to the maximum pressure at which liquid and gaseous phases can coexist.

Explanation:

This is a correct definition. At pressures above the critical pressure, a distinct liquid-gas phase boundary no longer exists, and the substance exists as a supercritical fluid.

13. Common Pressure Measurement Units

Statement: Pressure can be measured using the following units: ATM, BARS, PSI, Pascal, mm Hg.

Explanation:

These are indeed common units for measuring pressure, each with specific applications and conversion factors:

• ATM: Atmospheres
• BARS: Bar
• PSI: Pounds per Square Inch
• Pascal: SI unit of pressure (N/m²)
• mm Hg: Millimeters of Mercury (Torr)

14. The Zeroth Law of Thermodynamics

Statement: If two or more systems are in thermal contact with each other and are all in thermal equilibrium, this illustrates the Zeroth Law of Thermodynamics.

Explanation:

The Zeroth Law of Thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law forms the fundamental basis for temperature measurement and the concept of a thermometer.

15. Purpose of a Phase Diagram

Statement: A phase diagram serves to define a substance's physical state depending on temperature and pressure.

Explanation:

Phase diagrams graphically represent the conditions (temperature and pressure) at which different phases (solid, liquid, gas) of a substance can exist in equilibrium. They are crucial tools in materials science and engineering.