AP Chemistry Flashcards: Introduction to Entropy
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
A sample of helium gas is heated from 300 K to 400 K at constant pressure. What is the sign of the entropy change?
The entropy change is positive (+) because the increase in temperature leads to a broader distribution of kinetic energies, thus dispersing the energy more.
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A sample of helium gas is heated from 300 K to 400 K at constant pressure. What is the sign of the entropy change?
The entropy change is positive (+) because the increase in temperature leads to a broader distribution of kinetic energies, thus dispersing the energy more.
In the context of thermodynamics, what does entropy measure?
Entropy measures the dispersal of matter and energy within a system.
What is the general principle that determines whether entropy increases in a physical or chemical process?
Entropy increases whenever matter or energy becomes more dispersed in the system.
How does increasing the temperature of a system affect its entropy?
Increasing the temperature increases the system's entropy because the distribution of kinetic energies broadens, leading to greater energy dispersal.
What is the sign of the entropy change (ΔS) for the process of water freezing into ice?
The sign of the entropy change is negative (-) because the matter becomes less dispersed when changing from a liquid to a more ordered solid.
How does a substance's state of matter (solid, liquid, gas) relate to its entropy?
Entropy increases as a substance changes from solid to liquid to gas because the matter becomes progressively more dispersed.
In a chemical reaction involving gases, how does a change in the total moles of gas affect the system's entropy?
An increase in the total moles of gas during a reaction results in a positive entropy change (ΔS > 0) because the matter becomes more dispersed.
According to the Kinetic Molecular Theory (KMT), why does a temperature increase cause greater energy dispersal?
As temperature increases, the distribution of kinetic energies among the particles broadens, meaning there are more ways for the energy to be distributed, which corresponds to higher entropy.
Predict the sign of the entropy change (ΔS) for the reaction 2 H₂(g) + O₂(g) → 2 H₂O(g).
The entropy change (ΔS) is negative (-) because the total moles of gas decrease from 3 moles of reactants to 2 moles of product, making the system less dispersed.
A gas is allowed to expand into a larger container. What is the sign of the associated entropy change?
The sign of the entropy change is positive (+) because the gas particles become more dispersed as they occupy a larger volume.