AP Physics 2 Flashcards: The First Law Of Thermodynamics

What this deck covers

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

How to use these flashcards

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 First Law of Thermodynamics?

Answer: Energy cannot be created or destroyed, only transformed. Also known as conservation of energy principle.

Flashcard 2: What is the effect on $\triangle U$ if no heat is exchanged and the system does 25 J of work?

Answer: $\triangle U = -W = -25 \text{ J}$. All work comes from internal energy since $Q = 0$.

Flashcard 3: What is the work done if $\triangle U = 0$ and $Q = 100 \text{ J}$?

Answer: $W = Q = 100 \text{ J}$. In isothermal process, all heat becomes work output.

Flashcard 4: What is the First Law of Thermodynamics?

Answer: Energy cannot be created or destroyed, only transformed. Also known as conservation of energy principle.

Flashcard 5: Identify the process when $Q = W$ and $\triangle U = 0$.

Answer: Cyclic process. Process that returns to its initial thermodynamic state.

Flashcard 6: Identify the unit of energy in the First Law of Thermodynamics.

Answer: Joule (J). Standard SI unit for all forms of energy.

Flashcard 7: Calculate work done by a system with $\triangle U = 30 \text{ J}$ and $Q = 40 \text{ J}$.

Answer: $W = Q - \triangle U = 40 \text{ J} - 30 \text{ J} = 10 \text{ J}$. Rearranging the first law to solve for work done by system.

Flashcard 8: Calculate $\triangle U$ if $Q = -20 \text{ J}$ and $W = 10 \text{ J}$.

Answer: $\triangle U = Q - W = -20 \text{ J} - 10 \text{ J} = -30 \text{ J}$. System loses heat and has work done on it.

Flashcard 9: What does $W$ represent in the First Law of Thermodynamics?

Answer: Work done by the system. Energy transferred when system exerts force through displacement.

Flashcard 10: Find $Q$ if $\triangle U = -10 \text{ J}$ and $W = 5 \text{ J}$.

Answer: $Q = \triangle U + W = -10 \text{ J} + 5 \text{ J} = -5 \text{ J}$. System releases heat since $Q$ is negative.

Flashcard 11: What happens to $\triangle U$ if a system absorbs 50 J of heat and does no work?

Answer: $\triangle U = Q = 50 \text{ J}$. All absorbed heat increases internal energy since $W = 0$.

Flashcard 12: Calculate $\triangle U$ if $Q = 100 \text{ J}$ and $W = 60 \text{ J}$.

Answer: $\triangle U = Q - W = 100 \text{ J} - 60 \text{ J} = 40 \text{ J}$. Direct application of the first law formula.

Flashcard 13: What is the internal energy change if a closed system releases 50 J of heat and absorbs 50 J of heat?

Answer: $\triangle U = 0$. Equal heat in and out results in no net change.

Flashcard 14: Find the heat added if $\triangle U = 0 \text{ J}$ and $W = 50 \text{ J}$.

Answer: $Q = W = 50 \text{ J}$. Isothermal condition where heat input equals work output.

Flashcard 15: What is $\triangle U$ if $Q = 25 \text{ J}$ and $W = -25 \text{ J}$?

Answer: $\triangle U = Q - W = 25 \text{ J} - (-25 \text{ J}) = 50 \text{ J}$. Work done on system plus heat input both increase energy.

Flashcard 16: Identify the process when $Q = W$ and $\triangle U = 0$.

Answer: Cyclic process. Process that returns to its initial thermodynamic state.

Flashcard 17: What is the internal energy change if a closed system releases 50 J of heat and absorbs 50 J of heat?

Answer: $\triangle U = 0$. Equal heat in and out results in no net change.

Flashcard 18: What is the effect on $\triangle U$ if no heat is exchanged and the system does 25 J of work?

Answer: $\triangle U = -W = -25 \text{ J}$. All work comes from internal energy since $Q = 0$.

Flashcard 19: What does $\triangle U$ represent in the First Law of Thermodynamics?

Answer: Change in internal energy of the system. Represents the total energy change within the system.

Flashcard 20: Calculate $\triangle U$ if $W = -40 \text{ J}$ and $Q = 60 \text{ J}$.

Answer: $\triangle U = Q - W = 60 \text{ J} - (-40 \text{ J}) = 100 \text{ J}$. Negative work means work done on system adds to internal energy.

Flashcard 21: Identify the thermodynamic process with $Q = 0$ and $\triangle U = W$.

Answer: Adiabatic process. Process with no heat exchange, so $\triangle U = -W$.

Flashcard 22: Which sign does $Q$ have when heat is released by the system?

Answer: Negative. Heat flows out of the system, decreasing its energy.

Flashcard 23: What is the work done if $\triangle U = 0$ and $Q = 100 \text{ J}$?

Answer: $W = Q = 100 \text{ J}$. In isothermal process, all heat becomes work output.

Flashcard 24: Calculate $\triangle U$ if $Q = 100 \text{ J}$ and $W = 60 \text{ J}$.

Answer: $\triangle U = Q - W = 100 \text{ J} - 60 \text{ J} = 40 \text{ J}$. Direct application of the first law formula.

Flashcard 25: Determine the sign of $\triangle U$ if the system releases 30 J of heat and does 10 J of work.

Answer: Negative. $\triangle U = -30 - 10 = -40$ J, which is negative.

Flashcard 26: What does $\triangle U$ represent in the First Law of Thermodynamics?

Answer: Change in internal energy of the system. Represents the total energy change within the system.

Flashcard 27: What is the heat exchanged if $\triangle U = 10 \text{ J}$ and $W = 10 \text{ J}$?

Answer: $Q = \triangle U + W = 10 \text{ J} + 10 \text{ J} = 20 \text{ J}$. Total heat input considering both work and internal energy.

Flashcard 28: What does $Q$ represent in the First Law of Thermodynamics?

Answer: Heat added to the system. Energy transferred into or out of the system.

Flashcard 29: Identify the unit of energy in the First Law of Thermodynamics.

Answer: Joule (J). Standard SI unit for all forms of energy.

Flashcard 30: Identify the system's behavior if $\triangle U = 0$ and $Q = 0$.

Answer: Isolated system. System with no energy exchange and no work done.

Flashcard 31: Find $Q$ if $\triangle U = -10 \text{ J}$ and $W = 5 \text{ J}$.

Answer: $Q = \triangle U + W = -10 \text{ J} + 5 \text{ J} = -5 \text{ J}$. System releases heat since $Q$ is negative.

Flashcard 32: Determine $\triangle U$ for a system with $Q = 70 \text{ J}$ and $W = 50 \text{ J}$.

Answer: $\triangle U = Q - W = 70 \text{ J} - 50 \text{ J} = 20 \text{ J}$. Net energy increase since heat input exceeds work output.

Flashcard 33: Find the internal energy change if $Q = 0$ and $W = -25 \text{ J}$.

Answer: $\triangle U = -W = 25 \text{ J}$. Negative work means work is done on the system.

Flashcard 34: What is the work done if $Q = 20 \text{ J}$ and $\triangle U = 0 \text{ J}$?

Answer: $W = Q = 20 \text{ J}$. Isothermal process where all heat becomes work.

Flashcard 35: What is the relationship between $Q$, $W$, and $\triangle U$ in a cyclic process?

Answer: $\triangle U = 0$, so $Q = W$. System returns to initial state, so net heat equals net work.

Flashcard 36: What is the change in internal energy for an isolated system?

Answer: $\triangle U = 0$. No energy exchange with surroundings means no change.

Flashcard 37: What is the internal energy change when a system does 100 J of work and absorbs 50 J of heat?

Answer: $\triangle U = 50 \text{ J} - 100 \text{ J} = -50 \text{ J}$. Internal energy decreases as more work is done than heat absorbed.

Flashcard 38: Which sign does $Q$ have when heat is absorbed by the system?

Answer: Positive. Heat flows into the system, increasing its energy.

Flashcard 39: What occurs to $Q$ and $W$ in an isolated system?

Answer: Both $Q$ and $W$ are zero. No energy exchange possible in completely isolated system.

Flashcard 40: What happens to $\triangle U$ if a system absorbs 50 J of heat and does no work?

Answer: $\triangle U = Q = 50 \text{ J}$. All absorbed heat increases internal energy since $W = 0$.

Flashcard 41: What is the value of $W$ if $Q = 0$ and $\triangle U = 15 \text{ J}$?

Answer: $W = -\triangle U = -15 \text{ J}$. Work is negative since energy goes to internal energy.

Flashcard 42: Which sign does $W$ have when work is done on the system?

Answer: Negative. Surroundings perform work on the system, adding energy.

Flashcard 43: Determine $W$ if $Q = 30 \text{ J}$ and $\triangle U = -10 \text{ J}$.

Answer: $W = Q - \triangle U = 30 \text{ J} + 10 \text{ J} = 40 \text{ J}$. Note: $\triangle U$ is negative, so $W = 30 - (-10) = 40$ J.

Flashcard 44: Which sign does $Q$ have when heat is released by the system?

Answer: Negative. Heat flows out of the system, decreasing its energy.

Flashcard 45: Calculate $\triangle U$ if $W = -40 \text{ J}$ and $Q = 60 \text{ J}$.

Answer: $\triangle U = Q - W = 60 \text{ J} - (-40 \text{ J}) = 100 \text{ J}$. Negative work means work done on system adds to internal energy.

Flashcard 46: Which sign does $W$ have when work is done by the system?

Answer: Positive. System expends energy to perform work on surroundings.

Flashcard 47: Find the heat added if $\triangle U = 20 \text{ J}$ and $W = 15 \text{ J}$.

Answer: $Q = \triangle U + W = 20 \text{ J} + 15 \text{ J} = 35 \text{ J}$. Rearranging the first law to solve for heat input.

Flashcard 48: What is the change in internal energy for an isolated system?

Answer: $\triangle U = 0$. No energy exchange with surroundings means no change.

Flashcard 49: What is the internal energy change when a system does 100 J of work and absorbs 50 J of heat?

Answer: $\triangle U = 50 \text{ J} - 100 \text{ J} = -50 \text{ J}$. Internal energy decreases as more work is done than heat absorbed.

Flashcard 50: Identify the system's behavior if $\triangle U = 0$ and $Q = 0$.

Answer: Isolated system. System with no energy exchange and no work done.

Flashcard 51: What does $W$ represent in the First Law of Thermodynamics?

Answer: Work done by the system. Energy transferred when system exerts force through displacement.

Flashcard 52: Find the heat added if $\triangle U = 20 \text{ J}$ and $W = 15 \text{ J}$.

Answer: $Q = \triangle U + W = 20 \text{ J} + 15 \text{ J} = 35 \text{ J}$. Rearranging the first law to solve for heat input.

Flashcard 53: Determine $W$ if $Q = 30 \text{ J}$ and $\triangle U = -10 \text{ J}$.

Answer: $W = Q - \triangle U = 30 \text{ J} + 10 \text{ J} = 40 \text{ J}$. Note: $\triangle U$ is negative, so $W = 30 - (-10) = 40$ J.

Flashcard 54: Determine the sign of $\triangle U$ if the system releases 30 J of heat and does 10 J of work.

Answer: Negative. $\triangle U = -30 - 10 = -40$ J, which is negative.

Flashcard 55: Which sign does $Q$ have when heat is absorbed by the system?

Answer: Positive. Heat flows into the system, increasing its energy.

Flashcard 56: Which sign does $W$ have when work is done on the system?

Answer: Negative. Surroundings perform work on the system, adding energy.

Flashcard 57: Calculate $\triangle U$ if $Q = -20 \text{ J}$ and $W = 10 \text{ J}$.

Answer: $\triangle U = Q - W = -20 \text{ J} - 10 \text{ J} = -30 \text{ J}$. System loses heat and has work done on it.

Flashcard 58: What is the value of $Q$ if $\triangle U = -10 \text{ J}$ and $W = -10 \text{ J}$?

Answer: $Q = \triangle U + W = -10 \text{ J} - 10 \text{ J} = -20 \text{ J}$. Both terms are negative, indicating energy loss.

Flashcard 59: State the formula for the First Law of Thermodynamics.

Answer: $\triangle U = Q - W$. Where $U$ is internal energy, $Q$ is heat, and $W$ is work.

Flashcard 60: What is $\triangle U$ if $Q = 25 \text{ J}$ and $W = -25 \text{ J}$?

Answer: $\triangle U = Q - W = 25 \text{ J} - (-25 \text{ J}) = 50 \text{ J}$. Work done on system plus heat input both increase energy.

Flashcard 61: State the formula for the First Law of Thermodynamics.

Answer: $\triangle U = Q - W$. Where $U$ is internal energy, $Q$ is heat, and $W$ is work.

Flashcard 62: What is the heat exchanged if $\triangle U = 10 \text{ J}$ and $W = 10 \text{ J}$?

Answer: $Q = \triangle U + W = 10 \text{ J} + 10 \text{ J} = 20 \text{ J}$. Total heat input considering both work and internal energy.

Flashcard 63: What is the value of $W$ if $Q = 0$ and $\triangle U = 15 \text{ J}$?

Answer: $W = -\triangle U = -15 \text{ J}$. Work is negative since energy goes to internal energy.

Flashcard 64: What is the sign of $W$ if the system performs 20 J of work on the surroundings?

Answer: Positive. System does work on surroundings, so $W$ is positive.

Flashcard 65: What is the work done if $Q = 20 \text{ J}$ and $\triangle U = 0 \text{ J}$?

Answer: $W = Q = 20 \text{ J}$. Isothermal process where all heat becomes work.

Flashcard 66: Identify the thermodynamic process with $Q = 0$ and $\triangle U = W$.

Answer: Adiabatic process. Process with no heat exchange, so $\triangle U = -W$.

Flashcard 67: What is the value of $Q$ if $\triangle U = -10 \text{ J}$ and $W = -10 \text{ J}$?

Answer: $Q = \triangle U + W = -10 \text{ J} - 10 \text{ J} = -20 \text{ J}$. Both terms are negative, indicating energy loss.

Flashcard 68: Find the internal energy change if $Q = 0$ and $W = -25 \text{ J}$.

Answer: $\triangle U = -W = 25 \text{ J}$. Negative work means work is done on the system.

Flashcard 69: Which sign does $W$ have when work is done by the system?

Answer: Positive. System expends energy to perform work on surroundings.

Flashcard 70: What is the internal energy change for a system doing 15 J of work and absorbing 15 J of heat?

Answer: $\triangle U = Q - W = 15 \text{ J} - 15 \text{ J} = 0 \text{ J}$. Equal heat input and work output results in no change.

Flashcard 71: What occurs to $Q$ and $W$ in an isolated system?

Answer: Both $Q$ and $W$ are zero. No energy exchange possible in completely isolated system.

Flashcard 72: What is the internal energy change for a system doing 15 J of work and absorbing 15 J of heat?

Answer: $\triangle U = Q - W = 15 \text{ J} - 15 \text{ J} = 0 \text{ J}$. Equal heat input and work output results in no change.

Flashcard 73: Calculate work done by a system with $\triangle U = 30 \text{ J}$ and $Q = 40 \text{ J}$.

Answer: $W = Q - \triangle U = 40 \text{ J} - 30 \text{ J} = 10 \text{ J}$. Rearranging the first law to solve for work done by system.

Flashcard 74: What is the relationship between $Q$, $W$, and $\triangle U$ in a cyclic process?

Answer: $\triangle U = 0$, so $Q = W$. System returns to initial state, so net heat equals net work.

Flashcard 75: Determine $\triangle U$ for a system with $Q = 70 \text{ J}$ and $W = 50 \text{ J}$.

Answer: $\triangle U = Q - W = 70 \text{ J} - 50 \text{ J} = 20 \text{ J}$. Net energy increase since heat input exceeds work output.

Flashcard 76: What is the sign of $W$ if the system performs 20 J of work on the surroundings?

Answer: Positive. System does work on surroundings, so $W$ is positive.

Flashcard 77: Find the heat added if $\triangle U = 0 \text{ J}$ and $W = 50 \text{ J}$.

Answer: $Q = W = 50 \text{ J}$. Isothermal condition where heat input equals work output.

Flashcard 78: What does $Q$ represent in the First Law of Thermodynamics?

Answer: Heat added to the system. Energy transferred into or out of the system.