Thermodynamics Basics Quiz

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Questions and Answers

What sign convention is used when energy leaves the system?

The sign is (-) (correct)

There is no sign convention

The sign is (+)

The sign is (±)

Which of the following statements about entropy change (ΔS) is true?

ΔS is negative when the system's order decreases.

ΔS is positive when the system's disorder increases. (correct)

ΔS is positive when the system's disorder decreases.

ΔS is negative when the system's disorder increases.

What is true when work is done on the system?

Work is the same as heat.

Work is positive. (correct)

Work is negative.

Work is an irrelevant factor.

What defines the relationship between internal energy change (ΔU) and work (w)?

ΔU = q + w Signup and view all the answers

In a closed system, which equation reflects the relationship when volume is constant?

ΔU = qv Signup and view all the answers

What is the sign of ΔH when a reaction is exothermic?

ΔH is negative. Signup and view all the answers

According to the first law of thermodynamics, what is true about the change in internal energy of the universe?

ΔUuniv = 0 Signup and view all the answers

What happens in terms of energy when heat is added to a system?

Energy enters the system. Signup and view all the answers

Which type of system allows the transfer of both matter and energy?

Open system Signup and view all the answers

What distinguishes state functions from path functions in thermodynamics?

State functions are defined by final and initial values. Signup and view all the answers

In the context of thermodynamics, which of the following is considered an intensive property?

Temperature Signup and view all the answers

What happens to temperature when combining two equal masses of water at the same temperature?

It remains the same. Signup and view all the answers

Which of the following correctly describes extensive properties?

They are additive and depend on the amount of material. Signup and view all the answers

Which of the following statements about path functions is true?

They include variables like heat and work. Signup and view all the answers

A bomb calorimeter is defined as which type of thermodynamic system?

Isolated system Signup and view all the answers

Which of the following is not a characteristic of intensive properties?

They are additive when combined. Signup and view all the answers

Which statement about the conservation of internal energy is true?

The internal energy of the universe is conserved. Signup and view all the answers

In the equation ΔU = q + w, what does 'q' represent?

The heat exchanged by the system. Signup and view all the answers

When the internal energy change (ΔU) is calculated to be 4 kJ, what can be inferred?

The system has gained energy. Signup and view all the answers

What is the correct calculation of ΔU when 500 kJ of work is done by a system and it releases 300 kJ of energy as heat?

-800 kJ Signup and view all the answers

Which of the following statements about endothermic reactions is accurate?

Energy enters the system, making ΔH positive. Signup and view all the answers

Given the equation for enthalpy change (ΔH = Hproducts - Hreactants), how would you classify a reaction with a ΔH of 50 kJ?

Endothermic reaction. Signup and view all the answers

What value of q implies that heat is given off by the system?

-50 kJ Signup and view all the answers

If a reaction releases 250 kJ of energy and does 500 kJ of work, what is the total change in internal energy?

-750 kJ Signup and view all the answers

Study Notes

Open, Closed, and Isolated Systems

Open systems allow transfer of matter and energy
Closed systems allow transfer of energy, but not matter
Isolated systems do not allow transfer of matter or energy
Bomb calorimeters are examples of isolated systems due to insulation

State Functions vs Path Functions

State functions describe the initial and final states of a system
State functions are calculated as "final - initial"
Example: Temperature change in taking water from room temperature to sun, then to the North Pole and back to room temperature
Path functions consider the pathway or mechanism in a given process
Examples: Heat (q) and work (w)
Example: Work (w) done pushing a box around a room depends on the path taken

Extensive vs Intensive Properties

Extensive properties are additive
Examples: Volume, mass, moles, and energy
If you combine two buckets of water, the volume doubles
Intensive properties are not additive, they define a system
Examples: Temperature, density, and pressure
If you combine two buckets of water at 25 degrees Celsius the temperature remains at 25 degrees

Thermodynamic Signs

The sign of a thermodynamic variable is negative if it leaves the system
The sign of a thermodynamic variable is positive if it enters the system
For example: When heat (q) leaves the system, the sign is negative
ΔG is negative for a spontaneous process and positive for a non-spontaneous process
ΔS is positive for increasing disorder and negative for increasing order
ΔH is negative for an exothermic process and positive for an endothermic process

Heat vs Work

Heat is chaotic energy
Work is a concerted flow of energy that can be controlled
Both are path functions

Internal Energy and Enthalpy Theory

The first law of thermodynamics states that ΔUuniv = 0, meaning energy is conserved
ΔU = q + w
U (internal energy) is a measure of all potential and kinetic energy in a system
Calorimetry measures unknown ΔU reactions using ΔUsys = -ΔUsurrondings
ΔH = ΔU + PΔV
In a closed system, ΔU = qv, because volume is constant (no PΔV work)
In an open system, ΔH = qp, because pressure is constant

Calculating Internal Energy

Internal energy is calculated using the equation ΔU = q + w
For work: + indicates work is entering the system, - indicates work leaving the system
For heat: + indicates heat entering the system, - indicates heat leaving the system

Energy Diagrams of Reactions

Energy entering the system indicates a positive ΔU
Energy leaving the system indicates a negative ΔU
ΔH = Hproducts - Hreactants
An increase in energy on the energy diagram is endothermic
A decrease in energy on the energy diagram is exothermic

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Description

Test your understanding of open, closed, and isolated systems, as well as state functions versus path functions. This quiz also covers extensive and intensive properties, providing a comprehensive overview of thermodynamic principles. Perfect for students in chemistry or physics.