Thermodynamics Overview

What happens to the internal energy of a system if heat is added?

How is the internal energy of a system affected if work is done by the system?

If a gas experiences a loss of heat of 45 J and work of 450 J is done onto the system, what is the change in internal energy?

Which statement is true regarding heat leaving a system and its internal energy?

In the equation ΔU = Q - W, what does a positive Q indicate?

What does the first law of thermodynamics state regarding the change in internal energy of a system?

When is the work done by the system considered positive?

In an isothermal process, what is the condition of the change in internal energy?

How does an endothermic reaction differ from an exothermic reaction?

If a system absorbs 50 J of heat and does 30 J of work on its surroundings, what is the net change in its internal energy?

What happens to a system during an adiabatic process?

What is the result of combining 25 J of heat lost from a system with 4 J of work done on the system?

If a system undergoes an isolated process, what is the net change in internal energy?

Thermodynamics

Thermodynamics is the branch of science studying heat, temperature, and their relation to other energy forms.

Competencies

Explain the first law of thermodynamics
Explain enthalpy of a reaction

Thermochemistry

Exothermic: Releases energy (ΔH is negative)
Endothermic: Absorbs energy (ΔH is positive)
ΔH = change in enthalpy

Change in Enthalpy (ΔH)

ΔH = products - reactants
Positive ΔH = endothermic reaction
Negative ΔH = exothermic reaction

Heat and Work

Work can be used to create heat.
Heat can be used to create work.

System, Surroundings, and Boundary

A system is the specific part of the universe being studied.
Surroundings are the rest of the universe outside the system.
The boundary separates the system from the surroundings.
Internal Energy (U)

Two Types of Reactions

Exothermic: A reaction releasing energy in the form of heat from the system.
Endothermic: A reaction absorbing energy in the form of heat from the surroundings.

First Law of Thermodynamics

The change in internal energy (ΔU) of a system is equal to the heat added (Q) minus the work done by the system (W).
ΔU = Q - W
Q = heat added to the system
W = work done by the system

Sign Conventions

Q is positive if heat is added to the system.
Q is negative if heat leaves the system.
W is positive if work is done by the system.
W is negative if work is done on the system.
Examples of the first law and sign conventions calculation

Types of processes

Isovolumetric: Volume doesn't change, no work done (W = 0)
Isothermal: Temperature doesn't change, no change in internal energy (ΔU = 0)
Adiabatic: No energy transferred as heat (Q = 0)
Isolated system: No energy transferred as heat or work, no change in internal energy (ΔU = Q = W = 0)

Examples

Calculation examples for the first law of thermodynamics

Real-life applications

Various real-life examples related to the study of thermodynamics are presented to demonstrate the importance of understanding the concept.

Summary

If heat is added, internal energy increases.
If heat leaves, internal energy decreases.
If work is done by the system, internal energy decreases.
If work is done on the system, internal energy increases.

This quiz covers the fundamental concepts of thermodynamics, including the first law, enthalpy changes, and the differences between exothermic and endothermic reactions. Dive into the principles of heat, work, and the interactions within systems and their surroundings to test your understanding of this vital branch of science.