Enthalpy

In this episode, we explore the concept of enthalpy, a central idea in thermochemistry. Enthalpy measures the total energy in a system, including internal energy and the energy required to displace its surroundings. Listeners will learn how to understand enthalpy changes in chemical reactions, the role of enthalpy in determining whether a reaction absorbs or releases heat, and its practical significance. This foundational knowledge prepares learners for upcoming episodes on entropy, Gibbs free energy, and the laws of thermodynamics.

Check your understanding

These are the same multiple-choice questions you will see in the Quiz section after you listen to the episode. Use them here to preview or review the answers.

What does enthalpy (H) represent?

  1. The total energy of a system.
  2. The internal energy plus the product of pressure and volume.
  3. The energy required to break chemical bonds.
  4. The energy stored in reactants only.

What is true about an endothermic reaction?

  1. It releases heat to the surroundings.
  2. It absorbs heat from the surroundings.
  3. Its ∆H value is greater than zero.
  4. Its ∆H value is less than zero.

Which is an example of an exothermic process?

  1. Melting ice.
  2. Combustion of fuel.
  3. Evaporation of water.
  4. Freezing water.

How is the enthalpy change (∆H) calculated?

  1. H(reactants) - H(products).
  2. H(products) - H(reactants).
  3. The difference in bond strength of products and reactants.
  4. It cannot be calculated directly.

What does the enthalpy of formation (∆Hf°) represent?

  1. The heat change when one mole of a compound forms from its elements in their standard states.
  2. The heat change when a compound burns completely in oxygen.
  3. The energy required to break all bonds in one mole of a compound.
  4. The change in temperature of a system.

Suggested next

Related episodes that are a natural follow-on.

  • Endothermic process

    In this episode of the 'Thermochemistry' course, we explore endothermic processes, which absorb energy from their surroundings to proceed. Building on topics like enthalpy and entropy, this episode explains the key characteristics of endothermic reac… In this episode of the 'Thermochemistry' course, we explore endothermic processes, which absorb energy from their surroundings to proceed. Building on topics like enthalpy and entropy, this episode explains the key characteristics of endothermic reactions, examples such as melting ice or boiling water, and the role of energy input in breaking bonds. We'll also discuss how endothermic processes relate to thermodynamic principles and their significance in nature and industry. This episode sets the stage for understanding exothermic processes and the broader laws of thermodynamics.

  • Laws of thermodynamics

    In this episode of *Thermochemistry*, we delve into the fundamental Laws of Thermodynamics. These principles govern energy transfer, including heat, work, and entropy, forming the backbone of thermochemistry. You’ll learn about each law’s significanc… In this episode of *Thermochemistry*, we delve into the fundamental Laws of Thermodynamics. These principles govern energy transfer, including heat, work, and entropy, forming the backbone of thermochemistry. You’ll learn about each law’s significance, from the conservation of energy to the concept of entropy and absolute zero. Building on topics like enthalpy, entropy, and calorimetry, this episode solidifies your understanding of energy dynamics in chemical and physical systems. Ideal for enhancing your grasp of chemistry during your active time!

  • First law of thermodynamics

    In this episode, we delve into the First Law of Thermodynamics, a fundamental principle that governs energy conservation. We explore how energy is transferred in the form of heat and work, and how it relates to a system's internal energy. Building on… In this episode, we delve into the First Law of Thermodynamics, a fundamental principle that governs energy conservation. We explore how energy is transferred in the form of heat and work, and how it relates to a system's internal energy. Building on concepts like temperature and heat from previous episodes, we’ll illustrate the equation of the First Law and its applications in real-world systems, such as engines and refrigerators. This episode is a stepping stone to understanding the Second Law, entropy, and thermodynamic cycles in upcoming discussions.

  • Carnot cycle

    In this episode of the **Thermodynamics** course, we explore the Carnot cycle, a theoretical model that defines the maximum efficiency of a heat engine. We will discuss its four distinct stages—two isothermal and two adiabatic processes—and how these… In this episode of the **Thermodynamics** course, we explore the Carnot cycle, a theoretical model that defines the maximum efficiency of a heat engine. We will discuss its four distinct stages—two isothermal and two adiabatic processes—and how these steps relate to thermodynamic principles like entropy and the second law of thermodynamics. By understanding the Carnot cycle, listeners will gain insight into the limitations of real-world engines and the principles of energy transfer. This episode builds on prior discussions of heat engines and entropy and sets the stage for advanced topics like enthalpy in the next session.

  • Exothermic process

    Welcome to our episode on the chemistry of warmth! We will explore the fascinating world of exothermic processes, the direct opposite of the endothermic reactions we discussed previously. An exothermic process is any chemical reaction or physical cha… Welcome to our episode on the chemistry of warmth! We will explore the fascinating world of exothermic processes, the direct opposite of the endothermic reactions we discussed previously. An exothermic process is any chemical reaction or physical change that releases energy, usually as heat, causing its surroundings to warm up. From the comforting crackle of a bonfire to the instant heat of a chemical hand-warmer, we will delve into the molecular reasons for this energy release. You'll learn why the enthalpy change for these processes is negative, how we measure the heat using calorimetry, and what it takes to get these energy-releasing reactions started.

Often studied before

Episodes that tend to come earlier on similar paths.

  • Endothermic process

    In this episode of the 'Thermochemistry' course, we explore endothermic processes, which absorb energy from their surroundings to proceed. Building on topics like enthalpy and entropy, this episode explains the key characteristics of endothermic reac… In this episode of the 'Thermochemistry' course, we explore endothermic processes, which absorb energy from their surroundings to proceed. Building on topics like enthalpy and entropy, this episode explains the key characteristics of endothermic reactions, examples such as melting ice or boiling water, and the role of energy input in breaking bonds. We'll also discuss how endothermic processes relate to thermodynamic principles and their significance in nature and industry. This episode sets the stage for understanding exothermic processes and the broader laws of thermodynamics.

  • Gibbs free energy

    Why do some chemical reactions happen on their own while others need a push? In this episode, we introduce Gibbs free energy, a powerful concept that answers this very question. Building on our understanding of enthalpy from Hess's law and calorimetr… Why do some chemical reactions happen on their own while others need a push? In this episode, we introduce Gibbs free energy, a powerful concept that answers this very question. Building on our understanding of enthalpy from Hess's law and calorimetry, we'll explore the missing piece of the puzzle: entropy, the measure of disorder. You'll learn how the Gibbs free energy equation combines the drive for lower energy (enthalpy) and higher disorder (entropy) to predict whether a reaction will be spontaneous. This episode will equip you with the ultimate tool for forecasting chemical change.

  • Hess's law

    Welcome to the sixth episode of the Thermochemistry course! Building upon our previous discussions of thermochemistry, enthalpy, entropy, heat capacity, and calorimetry, this episode focuses on Hess's Law. Hess's Law is a fundamental principle that a… Welcome to the sixth episode of the Thermochemistry course! Building upon our previous discussions of thermochemistry, enthalpy, entropy, heat capacity, and calorimetry, this episode focuses on Hess's Law. Hess's Law is a fundamental principle that allows us to calculate the enthalpy change for a reaction that may be difficult or impossible to measure directly. We will explore the concept that enthalpy is a state function, the core principle behind Hess's law, and learn how to manipulate and combine known enthalpy changes of other reactions to determine the enthalpy change of the target reaction. This episode is essential for mastering thermochemical calculations and predicting the energy changes in complex chemical processes. It will form the basis of your understanding for future lessons, such as Gibbs Free Energy.

  • First law of thermodynamics

    In this episode, we delve into the First Law of Thermodynamics, a fundamental principle that governs energy conservation. We explore how energy is transferred in the form of heat and work, and how it relates to a system's internal energy. Building on… In this episode, we delve into the First Law of Thermodynamics, a fundamental principle that governs energy conservation. We explore how energy is transferred in the form of heat and work, and how it relates to a system's internal energy. Building on concepts like temperature and heat from previous episodes, we’ll illustrate the equation of the First Law and its applications in real-world systems, such as engines and refrigerators. This episode is a stepping stone to understanding the Second Law, entropy, and thermodynamic cycles in upcoming discussions.

  • Heat capacity

    In this episode, we delve into the concept of heat capacity, a fundamental principle in thermochemistry. You’ll learn what heat capacity is, how it differs from specific heat, and why it is crucial for understanding energy transfer in physical and ch… In this episode, we delve into the concept of heat capacity, a fundamental principle in thermochemistry. You’ll learn what heat capacity is, how it differs from specific heat, and why it is crucial for understanding energy transfer in physical and chemical processes. We’ll explore its role in daily phenomena, scientific applications, and its mathematical relationship with energy, temperature, and mass. This episode prepares you for deeper topics like calorimetry and Hess's law, bridging foundational knowledge with practical applications in thermodynamics.