Chapter 1 - Intro to Thermo

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Questions and Answers

What happens to the state of a system when any of its properties change?

The state remains the same

The state becomes equilibrium

The state becomes isolated

The state is said to have undergone a processn (correct)

Which of the following is an example of an extensive property?

Pressure

Mass (correct)

Density

Temperature

What characterizes intensive properties?

They vary with time but not with position

They are independent of the system size (correct)

They depend on the size of the system

They can be added for a whole system

What is an equilibrium state?

A stable state where no internal changes occur Signup and view all the answers

Which of the following statements about units is correct?

Different systems of units can define the same quantity Signup and view all the answers

How is force defined in terms of mass and acceleration?

F = ma Signup and view all the answers

What is the relationship between the values of extensive properties in a divided system?

They sum up to equal the value of the overall system Signup and view all the answers

Which of the following factors does NOT impact an intensive property?

Size of the system Signup and view all the answers

What defines density at a point in a substance treated as a continuum?

The limit of the mass to the smallest volume Signup and view all the answers

Which unit is used to express density in SI units?

kg/m3 Signup and view all the answers

What is the specific volume of a substance?

Volume per unit mass Signup and view all the answers

What is absolute pressure defined as?

Pressure measured against a vacuum Signup and view all the answers

Which of the following is a true statement about gage pressure?

It is used when system pressure exceeds atmospheric pressure Signup and view all the answers

What is the SI unit for pressure?

N/m2 Signup and view all the answers

What is the specific volume's relationship to density?

It is the reciprocal of density Signup and view all the answers

Which of the following describes pressure at a point in a fluid at rest?

It acts in all directions equally Signup and view all the answers

What defines a closed system in thermodynamics?

It contains the same matter and does not allow mass transfer. Signup and view all the answers

Which of the following describes a control volume?

A defined space where mass can flow across its boundaries. Signup and view all the answers

What is classified as an extensive property?

Mass Signup and view all the answers

What happens in an isolated system?

No interaction occurs with surroundings for mass or energy. Signup and view all the answers

How is the temperature measured in the Kelvin scale?

It is equivalent to the Celsius scale plus 273.15. Signup and view all the answers

Which statement most accurately reflects the difference between macroscopic and microscopic approaches?

Microscopic approach focuses on statistical methods of average particle behavior, while macroscopic observes measurable effects. Signup and view all the answers

What does the state of a system convey?

It is described by specific properties such as pressure and volume. Signup and view all the answers

What is a property in the context of thermodynamics?

A macroscopic feature that has a defined numerical value at a given time. Signup and view all the answers

What is the formula for calculating gauge pressure?

p(gage) = p(absolute) – patm(absolute) Signup and view all the answers

Which of the following thermometric properties is utilized in a liquid-in-glass thermometer?

Length of the liquid column Signup and view all the answers

When does thermal equilibrium occur between two blocks?

When no changes in observable properties occur Signup and view all the answers

Which temperature scale uses absolute zero as its reference point alongside the Kelvin scale?

Rankine Signup and view all the answers

What does the formula T(oR) = 1.8T(K) convey?

Conversion from Kelvin to Rankine Signup and view all the answers

In the field of engineering design, what is NOT considered a fundamental element?

Choosing materials Signup and view all the answers

What is the primary implication of having atmospheric pressure greater than system pressure?

The system experiences vacuum pressure Signup and view all the answers

What does the term 'thermometric substance' refer to?

A substance that exhibits a change in thermometric property Signup and view all the answers

Study Notes

Chapter 1: Getting Started

This chapter introduces introductory concepts and definitions.
Learning outcomes include explaining fundamental concepts (closed system, control volume, boundary, surroundings, property, state, process, extensive and intensive properties, and equilibrium).

Learning Outcomes

Identify SI and English Engineering units, including specific volume, pressure, and temperature.
Describe relationships among Kelvin, Rankine, Celsius, and Fahrenheit temperature scales; and apply appropriate unit conversion factors.
Apply problem-solving methodology.

Defining Systems

System: The part of the universe being studied.
Surroundings: Everything external to the system.
Boundary: Separates the system from its surroundings.

Control Mass or Closed System

A system that always contains the same matter.
No mass transfer across the boundary.
Energy transfer across the boundary is permitted.
An isolated system is a special type of closed system that does not interact with its surroundings in any way—no mass or energy interaction.

Control Volume or Open System

A region of space where mass flows.
Mass and energy cross the boundary of a control volume.

Macroscopic and Microscopic Views

Macroscopic view: Describes system behavior in terms of gross effects such as pressure and temperature that can be measured by instruments (e.g., pressure gauges, thermometers).
Microscopic view: Characterizes a system by statistical means using the average behavior of particles.

Property

A macroscopic characteristic of a system that can be assigned a numerical value without knowing the previous behavior of the system.
Examples include volume, energy, pressure, and temperature.

State

The condition of a system described by its properties.
The state can often be specified by providing the values of a subset of its properties.
Example: State of a gas is often described by p, V, and T.

Process

A transformation from one state to another.
When any of the properties of a system changes, the state changes, and the system undergoes a process.
Example: If the volume of a system changes from V₁ to V₂, there is the process from State 1 to State 2. Property value changes.

Extensive Property

A property that depends on the size or extent of a system.
Examples include mass, volume, and energy.
The value for an extensive property of an overall system is the sum of the values for the parts it's divided into.

Intensive Property

A property that is independent of the size or extent of a system.
Examples include pressure and temperature.
Its value is not additive as for extensive properties.

Equilibrium

A state where a system does not interact with its surroundings but its state may change via internal spontaneous events.
Intensive properties such as temperature and pressure tend towards uniform values.
All such changes cease, the system is at an equilibrium state.
Equilibrium states and processes play an important role in thermodynamic analysis.

Units (1 of 2)

A unit is a specified amount of a quantity used for comparison.
Examples include meters, feet, and miles for length.
Two systems of units: SI (Système International d'Unités) and English Engineering units.

Units (2 of 2)

Table 1.3 shows units for mass, length, time, and force in SI and English units.
Base units for mass, length, and time and force has a unit derived from them using F=ma (Eq.1.1)

Density (p) and Specific Volume (v)

From a macroscopic perspective, matter is treated as continuously distributed.
Density is mass per unit volume (p = m/V).
Density is an intensive property that can vary from point to point.
Specific volume is the reciprocal of density (v = 1/p).
Specific volume is an intensive property.
SI: (kg/m³), English:(lb/ft³).

Pressure (p)

Pressure in a fluid at rest is defined as the limit, where F_normal is the force normal to the area, and A is the area (p = lim F_normal/A_{→ A'} as A→A').
The force that the fluid exerts on one side of the area has an equal but oppositely directed force exerted by the fluid on the other side.

Pressure Units

SI unit of pressure is the pascal (Pa).
1 Pa = 1 N/m².
Other units include kPa, bar, and MPa.
English units include lbf/ft² and lbf/in².

Absolute Pressure

Pressure measured with respect to a complete vacuum.
Absolute pressure must be used in thermodynamic relations.

Gage and Vacuum Pressure

Gage pressure is the difference between the absolute pressure of a system and atmospheric pressure.
Vacuum pressure is the difference between atmospheric pressure and the absolute pressure of a system.

Temperature (T)

Temperature is the property that determines if two objects are in thermal equilibrium.
If two objects are in contact and isolated, they will interact thermally until they are in thermal equilibrium.

Thermometers (1 of 2)

Any object with a measurable property that changes with temperature can be used as a thermometer.
A thermometric property is a property that changes with temperature.
The substance that exhibits changes in the thermometric property is called a thermometric substance.

Thermometers (2 of 2)

Example: Liquid-in-glass thermometer.
Other types include thermocouples, thermistors, and radiation thermometers.

Temperature Scales

Kelvin, Rankine, Celsius, and Fahrenheit scales.
Kelvin is the SI base unit for temperature.
Rankine is an English base unit.
Formulas for conversions between these scales.

Design

Engineering design is a decision-making process.
Fundamental elements include establishing objectives, synthesis, analysis, construction, testing, and evaluation.
Design is constrained by factors including economics, safety and environmental impact.

Problem-Solving Methodology

Known: Identify what is known.
Find: State what is to be determined.
Schematic and Given Data: Sketch and label relevant data.
Engineering Model: List assumptions and idealizations.
Analysis: Reduce equations to produce desired results.

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Description

Test your understanding of fundamental concepts in thermodynamics through this quiz. Explore the differences between extensive and intensive properties, definitions of pressure, and equilibrium states. Perfect for students looking to reinforce their knowledge in the subject.