Hess's Law
Definition
Hess's Law states that the total enthalpy change for a chemical reaction is independent of the pathway or number of steps taken to achieve the reaction. It only depends on the initial and final states.
Analogy
Think of Hess's law like traveling from your home to school. You can take different routes - maybe one day you walk, another day you ride a bike, or perhaps you take a bus. No matter how you get there, the distance between your home and school doesn't change. Similarly, no matter what path or steps a chemical reaction takes, its total energy change remains constant.
Related terms
Enthalpy: This is the heat content of a system at constant pressure. It's like measuring how much energy (or "heat") is in your lunchbox if it couldn't leak out anywhere.
Endothermic Reaction: This type of reaction absorbs heat from its surroundings during its process. Imagine this as an ice cream cone absorbing heat on a hot summer day and melting.
Exothermic Reaction: In contrast to endothermic reactions, exothermic reactions release heat into their surroundings. Picture this as lighting up a firework; once ignited, it releases light and heat into the air around it.
"Hess's Law" appears in:
Study guides (2)
Practice Questions (5)
- Hess's Law is based on which of the following principles?
- In a Hess's Law calculation, if a reaction is reversed, which of the following must also be done?
- When using Hess's Law, which of the following is true?
- Hess's Law can be used to calculate which of the following?
- Which of the following is a statement of Hess's Law?
Resources
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