Podcast
Questions and Answers
What does the Second Law of Thermodynamics state about energy transfers?
What does the Second Law of Thermodynamics state about energy transfers?
- Energy transfers decrease the entropy of the universe.
- Every energy transfer increases the entropy of the universe. (correct)
- Entropy remains constant during energy transformations.
- Energy transfers are always fully efficient.
Which state of matter has the highest entropy?
Which state of matter has the highest entropy?
- Crystalline structure
- Solid
- Liquid
- Gas (correct)
Why is the reaction A→B+C more likely to occur than B+C→A?
Why is the reaction A→B+C more likely to occur than B+C→A?
- It requires less energy input.
- It reduces the number of molecules present.
- It leads to an increase in entropy. (correct)
- It is an endothermic reaction.
Which example represents a spontaneous endothermic process?
Which example represents a spontaneous endothermic process?
What does increasing disorder in a system suggest about its entropy?
What does increasing disorder in a system suggest about its entropy?
What does the Zeroth Law of Thermodynamics state?
What does the Zeroth Law of Thermodynamics state?
According to the First Law of Thermodynamics, which of the following is true?
According to the First Law of Thermodynamics, which of the following is true?
Which of the following represents the relationship defined by the First Law of Thermodynamics?
Which of the following represents the relationship defined by the First Law of Thermodynamics?
What does the Second Law of Thermodynamics imply about isolated systems?
What does the Second Law of Thermodynamics imply about isolated systems?
At absolute zero, what can be said about the entropy of a system?
At absolute zero, what can be said about the entropy of a system?
Flashcards
Zeroth Law of Thermodynamics
Zeroth Law of Thermodynamics
Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other.
First Law of Thermodynamics
First Law of Thermodynamics
The internal energy of an isolated system is constant; energy can change form but cannot be created or destroyed.
Second Law of Thermodynamics
Second Law of Thermodynamics
The entropy of an isolated system tends to increase.
Third Law of Thermodynamics
Third Law of Thermodynamics
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First Law Equation
First Law Equation
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Entropy
Entropy
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Free Energy
Free Energy
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Spontaneous Reaction
Spontaneous Reaction
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Why do spontaneous reactions occur?
Why do spontaneous reactions occur?
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Study Notes
Thermodynamics Overview
- Thermodynamics is the study of energy and its transformations.
- The zeroth law of thermodynamics defines thermal equilibrium. If two systems are separately in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
- The first law of thermodynamics states that energy is conserved in an isolated system. Energy can change form, but it can’t be created or destroyed.
- The second law of thermodynamics states that the total entropy of an isolated system can only increase over time. Entropy is a measure of disorder in a system. Heat flows naturally from a hotter to a colder body.
- The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero. Entropies are zero at absolute zero.
Gibbs Free Energy
- Gibbs free energy is a thermodynamic potential that measures the maximum reversible work that may be performed by a thermodynamic system at a constant temperature and pressure.
- Gibbs free energy (G) is a thermodynamic state function.
- A change in Gibbs free energy (â–³G) predicts the spontaneity of a reaction at constant temperature and pressure.
- If â–³G is negative, the process is spontaneous.
- If â–³G is zero, the system is at equilibrium.
- If â–³G is positive, the process is not spontaneous under those conditions.
Gibbs Free Energy Calculations
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The change in Gibbs free energy is calculated by â–³G = â–³H - Tâ–³S.
- â–³G = change in Gibbs free energy
- â–³H = change in enthalpy
- T = temperature in Kelvin
- â–³S = change in entropy
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For a reaction A + B → C + D: △G = △G° + RTln ([C][D] / [A][B])
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△G° is the Gibbs free energy change under standard conditions.
Coupled Reactions
- Cells use the energy released from exergonic reactions to drive endergonic reactions.
- Coupled reactions are spontaneous overall.
ATP Hydrolysis
- ATP hydrolysis is an exergonic reaction, releasing free energy.
- ATP → ADP + Pi + Energy
- ATP hydrolysis is crucial for various cellular processes.
- ATP hydrolysis alters the position of equilibrium by a factor of ~108.
Activation by Phosphorylation
- ATP can drive endergonic reactions by transferring a phosphate group to a reactant—this is phosphorylation.
- The recipient molecule becomes phosphorylated as part of the process.
Living Organisms and Entropy
- Organisms are highly ordered systems, but the second law of thermodynamics demands an increase in entropy.
- Organisms fight entropy by taking in energy and releasing heat.
- The sun is a source of free energy.
- Photosynthesis converts oxidized carbon (CO2) to reduced carbon (sugar, CH2O).
- Respiration releases energy from reduced substances.
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