Chapter 2: The Heat of the Journey
The twins encounter Sunny and Shady, and learn about energy flow...
As the Thermal Twins journeyed through a meadow, they spotted two cloud sprites engaged in a fierce tug-of-war with what looked like a giant thermometer.
"I'm Sunny," announced the sprite glowing with warm orange light. "I give out heat to everything around me!"
"And I'm Shady," said the other sprite, surrounded by a cool blue aura. "I take in heat from my surroundings."
Enthalpy stepped forward, fascinated. "So you're exothermic," he said to Sunny, "releasing energy in the form of heat. That means your ΔH is negative!"
"And you're endothermic," Entropy said to Shady, "absorbing energy as heat. Your ΔH is positive!"
Gibbs the Guide nodded approvingly. "Remember, twins, when energy is released to the surroundings, the system becomes more stable. But when energy is absorbed, the system becomes less stable."
Enthalpy Change
Enthalpy (ΔH) measures heat transfer during a reaction at constant pressure. Negative ΔH means heat is released (exothermic). Positive ΔH means heat is absorbed (endothermic).
Common Questions:
What is an exothermic reaction?
An exothermic reaction releases heat to the surroundings, resulting in a negative enthalpy change (ΔH < 0). This is represented by Sunny in our story, who gives out heat to everything around him.
What is an endothermic reaction?
An endothermic reaction absorbs heat from the surroundings, resulting in a positive enthalpy change (ΔH > 0). This is represented by Shady in our story, who takes in heat from the surroundings.
How does enthalpy affect stability?
When energy is released to the surroundings (negative ΔH), the system becomes more stable. When energy is absorbed (positive ΔH), the system becomes less stable.