AP Physics 2 Flashcards: Entropy And Second Law Of Thermodynamics

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This deck focuses on Entropy And Second Law Of Thermodynamics, giving you a quick way to review the definitions, rules, and examples that matter most for AP Physics 2.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the Second Law of Thermodynamics?

Answer: Entropy of an isolated system never decreases. This fundamental law states entropy never decreases in isolated systems.

Flashcard 2: What is the significance of $\Omega$ in Boltzmann's equation?

Answer: Number of microstates. Represents the total number of possible microscopic arrangements.

Flashcard 3: What is the Third Law of Thermodynamics?

Answer: Entropy approaches zero as temperature approaches absolute zero. Perfect crystals reach minimum entropy at 0 K.

Flashcard 4: What does the Second Law imply about perpetual motion machines?

Answer: They are impossible. Entropy increase prevents 100% efficient energy conversion.

Flashcard 5: State the units of entropy in the SI system.

Answer: Joules per Kelvin (J/K). Energy per temperature unit in the International System of Units.

Flashcard 6: What does a negative entropy change indicate?

Answer: Decreased disorder or energy dispersal. Negative $\Delta S$ means the system becomes more ordered.

Flashcard 7: Define entropy.

Answer: Entropy is a measure of a system's disorder. Entropy quantifies the randomness or energy dispersal in a system.

Flashcard 8: State the sign of entropy change for a spontaneous reaction.

Answer: Positive. Spontaneous processes always increase total system entropy.

Flashcard 9: Define entropy.

Answer: Entropy is a measure of a system's disorder. Entropy quantifies the randomness or energy dispersal in a system.

Flashcard 10: What is the significance of the Third Law for entropy?

Answer: Entropy becomes constant at absolute zero. All substances reach minimum entropy at absolute zero temperature.

Flashcard 11: What is the formula for change in entropy?

Answer: $\Delta S = \frac{Q}{T}$. Heat $Q$ divided by temperature $T$ gives entropy change.

Flashcard 12: What is the effect of entropy on energy dispersal?

Answer: Higher entropy means greater energy dispersal. Energy spreads out more uniformly with increasing entropy.

Flashcard 13: What is the statistical interpretation of entropy?

Answer: Entropy relates to the number of microstates. More microstates correspond to higher entropy values.

Flashcard 14: In which type of process does total entropy change equal zero?

Answer: Reversible process. Only reversible processes maintain constant total entropy.

Flashcard 15: What happens to entropy in an isolated system over time?

Answer: Entropy increases or remains constant. Second Law prevents entropy decrease in isolated systems.

Flashcard 16: What is the Second Law of Thermodynamics?

Answer: Entropy of an isolated system never decreases. This fundamental law states entropy never decreases in isolated systems.

Flashcard 17: What is the relationship between entropy and temperature?

Answer: Entropy increases with temperature. Higher temperatures allow more molecular motion and disorder.

Flashcard 18: What is the entropy change for an isothermal process?

Answer: $\Delta S = \frac{Q}{T}$. For constant temperature, entropy change equals $Q/T$.

Flashcard 19: What is the effect of entropy on energy dispersal?

Answer: Higher entropy means greater energy dispersal. Energy spreads out more uniformly with increasing entropy.

Flashcard 20: Calculate the entropy change for $Q = 150 \, J$ and $T = 75 \, K$.

Answer: $\Delta S = 2 \, J/K$. Using $\Delta S = Q/T = 150/75 = 2$ J/K.

Flashcard 21: What is the entropy change for an isothermal process?

Answer: $\Delta S = \frac{Q}{T}$. For constant temperature, entropy change equals $Q/T$.

Flashcard 22: What does a negative entropy change indicate?

Answer: Decreased disorder or energy dispersal. Negative $\Delta S$ means the system becomes more ordered.

Flashcard 23: What is the significance of $\Omega$ in Boltzmann's equation?

Answer: Number of microstates. Represents the total number of possible microscopic arrangements.

Flashcard 24: Which principle dictates that entropy never decreases?

Answer: Second Law of Thermodynamics. This law mandates entropy never decreases in isolated systems.

Flashcard 25: Calculate entropy change for $Q = 500 \, J$ and $T = 300 \, K$.

Answer: $\Delta S = 1.67 \, J/K$. Using $\Delta S = Q/T = 500/300 = 1.67$ J/K.

Flashcard 26: Which physical law relates to energy's ability to do work?

Answer: Second Law of Thermodynamics. Entropy increase limits the conversion of heat to work.

Flashcard 27: What is the relationship between entropy and temperature?

Answer: Entropy increases with temperature. Higher temperatures allow more molecular motion and disorder.

Flashcard 28: Identify the symbol for entropy.

Answer: S. Standard symbol used to represent entropy in thermodynamic equations.

Flashcard 29: What does a decrease in entropy mean for a system?

Answer: The system becomes more ordered. Negative $\Delta S$ indicates reduced randomness and fewer microstates.

Flashcard 30: What does the Second Law imply about perpetual motion machines?

Answer: They are impossible. Entropy increase prevents 100% efficient energy conversion.

Flashcard 31: What is the relationship between entropy and heat exchange?

Answer: Entropy change is proportional to heat exchange. More heat transfer at lower temperatures increases entropy more.

Flashcard 32: How does entropy impact heat engine efficiency?

Answer: Higher entropy reduces efficiency. Rising entropy means less available energy for useful work.

Flashcard 33: What is the formula for change in entropy?

Answer: $\Delta S = \frac{Q}{T}$. Heat $Q$ divided by temperature $T$ gives entropy change.

Flashcard 34: How does entropy affect the feasibility of chemical reactions?

Answer: Reactions tend to increase total entropy. Reactions favored when they increase overall system entropy.

Flashcard 35: State the equation for entropy change during phase transition.

Answer: $\Delta S = \frac{\Delta H}{T}$. Enthalpy change divided by temperature during phase changes.

Flashcard 36: What does entropy measure in a thermodynamic system?

Answer: Disorder or randomness. Quantifies the degree of molecular chaos or energy spread.

Flashcard 37: How does entropy change in irreversible processes?

Answer: Entropy increases. All real processes are irreversible, so entropy always increases.

Flashcard 38: What is the Third Law of Thermodynamics?

Answer: Entropy approaches zero as temperature approaches absolute zero. Perfect crystals reach minimum entropy at 0 K.

Flashcard 39: How does entropy impact heat engine efficiency?

Answer: Higher entropy reduces efficiency. Rising entropy means less available energy for useful work.

Flashcard 40: What happens to entropy in an isolated system over time?

Answer: Entropy increases or remains constant. Second Law prevents entropy decrease in isolated systems.

Flashcard 41: What is the significance of the Third Law for entropy?

Answer: Entropy becomes constant at absolute zero. All substances reach minimum entropy at absolute zero temperature.

Flashcard 42: Which principle dictates that entropy never decreases?

Answer: Second Law of Thermodynamics. This law mandates entropy never decreases in isolated systems.

Flashcard 43: Identify the symbol for entropy.

Answer: S. Standard symbol used to represent entropy in thermodynamic equations.

Flashcard 44: Define a microstate in statistical mechanics.

Answer: A specific configuration of a system's particles. One possible arrangement of all particles in the system.

Flashcard 45: What is the relationship between entropy and heat exchange?

Answer: Entropy change is proportional to heat exchange. More heat transfer at lower temperatures increases entropy more.

Flashcard 46: What does a decrease in entropy mean for a system?

Answer: The system becomes more ordered. Negative $\Delta S$ indicates reduced randomness and fewer microstates.

Flashcard 47: Calculate the entropy change for $Q = 150 \, J$ and $T = 75 \, K$.

Answer: $\Delta S = 2 \, J/K$. Using $\Delta S = Q/T = 150/75 = 2$ J/K.

Flashcard 48: What does a positive change in entropy indicate?

Answer: Increased disorder in the system. Positive $\Delta S$ means more microstates and greater randomness.

Flashcard 49: Which physical law relates to energy's ability to do work?

Answer: Second Law of Thermodynamics. Entropy increase limits the conversion of heat to work.

Flashcard 50: Define the term 'macrostate'.

Answer: A set of conditions defining a system's state. Observable properties like temperature and pressure define macrostates.

Flashcard 51: What does $k$ represent in Boltzmann's formula?

Answer: Boltzmann's constant. Fundamental physical constant linking microscopic and macroscopic properties.

Flashcard 52: Find the entropy change for $Q = 100 \, J$ and $T = 25 \, K$.

Answer: $\Delta S = 4 \, J/K$. Using $\Delta S = Q/T = 100/25 = 4$ J/K.

Flashcard 53: What is the entropy change for an adiabatic process?

Answer: $\Delta S = 0$. No heat transfer means no entropy change in ideal case.

Flashcard 54: State the units of entropy in the SI system.

Answer: Joules per Kelvin (J/K). Energy per temperature unit in the International System of Units.

Flashcard 55: What does a positive change in entropy indicate?

Answer: Increased disorder in the system. Positive $\Delta S$ means more microstates and greater randomness.

Flashcard 56: State the equation for entropy change during phase transition.

Answer: $\Delta S = \frac{\Delta H}{T}$. Enthalpy change divided by temperature during phase changes.

Flashcard 57: Find the entropy change for $Q = 100 \, J$ and $T = 25 \, K$.

Answer: $\Delta S = 4 \, J/K$. Using $\Delta S = Q/T = 100/25 = 4$ J/K.

Flashcard 58: Describe the entropy of a perfect crystal at absolute zero.

Answer: Entropy is zero. Perfect order at absolute zero means minimum possible entropy.

Flashcard 59: Which law applies to the direction of spontaneous processes?

Answer: Second Law of Thermodynamics. Entropy increase determines which processes occur naturally.

Flashcard 60: What is the statistical interpretation of entropy?

Answer: Entropy relates to the number of microstates. More microstates correspond to higher entropy values.

Flashcard 61: What is the typical outcome for entropy when mixing gases?

Answer: Entropy increases. Mixing creates more possible molecular arrangements and disorder.

Flashcard 62: Define the term 'macrostate'.

Answer: A set of conditions defining a system's state. Observable properties like temperature and pressure define macrostates.

Flashcard 63: How does entropy affect the feasibility of chemical reactions?

Answer: Reactions tend to increase total entropy. Reactions favored when they increase overall system entropy.

Flashcard 64: What is the condition for a process to be reversible?

Answer: Total entropy change is zero. No net entropy increase means the process is reversible.

Flashcard 65: What is the entropy change for an adiabatic process?

Answer: $\Delta S = 0$. No heat transfer means no entropy change in ideal case.

Flashcard 66: What does entropy measure in a thermodynamic system?

Answer: Disorder or randomness. Quantifies the degree of molecular chaos or energy spread.

Flashcard 67: Describe the entropy of a perfect crystal at absolute zero.

Answer: Entropy is zero. Perfect order at absolute zero means minimum possible entropy.

Flashcard 68: Which law applies to the direction of spontaneous processes?

Answer: Second Law of Thermodynamics. Entropy increase determines which processes occur naturally.

Flashcard 69: State Boltzmann's entropy formula.

Answer: $S = k \ln \Omega$. Relates entropy $S$ to number of microstates $\Omega$.

Flashcard 70: What is the condition for a process to be reversible?

Answer: Total entropy change is zero. No net entropy increase means the process is reversible.

Flashcard 71: State Boltzmann's entropy formula.

Answer: $S = k \ln \Omega$. Relates entropy $S$ to number of microstates $\Omega$.

Flashcard 72: What is the role of entropy in the heat death of the universe?

Answer: Entropy maximizes, leading to uniform energy distribution. Maximum entropy means complete thermal equilibrium throughout the universe.

Flashcard 73: What is the role of entropy in the heat death of the universe?

Answer: Entropy maximizes, leading to uniform energy distribution. Maximum entropy means complete thermal equilibrium throughout the universe.

Flashcard 74: Define a microstate in statistical mechanics.

Answer: A specific configuration of a system's particles. One possible arrangement of all particles in the system.

Flashcard 75: State the sign of entropy change for a spontaneous reaction.

Answer: Positive. Spontaneous processes always increase total system entropy.

Flashcard 76: Calculate entropy change for $Q = 500 \, J$ and $T = 300 \, K$.

Answer: $\Delta S = 1.67 \, J/K$. Using $\Delta S = Q/T = 500/300 = 1.67$ J/K.

Flashcard 77: What is the typical outcome for entropy when mixing gases?

Answer: Entropy increases. Mixing creates more possible molecular arrangements and disorder.