Thermodynamics, Important Topics Explanation, Download PDF

Thermodynamics is a key branch of science that explains how energy flows during chemical reactions and physical changes. Students need to understand the relationship between heat, work, and energy in various processes. For NEET aspirants, learning thermodynamics helps in solving problems related to energy changes, spontaneity, and equilibrium in chemical reactions.

Furthermore, thermodynamics helps students connect theory with practical applications. For example, it explains why ice melts, why reactions release or absorb heat, and how systems reach equilibrium. Grasping these concepts helps aspirants to answer questions accurately and develop a strong conceptual understanding.

Thermodynamics Explained

Thermodynamics studies how energy is transferred in systems during chemical and physical changes. It focuses on understanding how heat, work, and energy interact. For example, when ice melts, heat is absorbed, increasing internal energy and changing the physical state from solid to liquid.

Energy can neither be created nor destroyed. This means that energy only changes from one form to another, such as from heat to work or potential energy to kinetic energy. Thermodynamic systems can be open, closed, or isolated. And, understanding these types helps students analyse reactions correctly. It should be noted that heat is the energy transfer due to temperature differences. Further, work is energy transferred when a force moves an object or changes volume. By studying energy changes, students can determine whether reactions are spontaneous and how much energy is involved.

Note: Understanding thermodynamics allows aspirants to apply energy concepts to various NEET questions efficiently.

State and Path Functions

State and path functions describe how energy and properties change in a system. State functions depend only on the system’s current condition, while path functions depend on the way the process happens or the route taken to reach that state.

• State functions include pressure, volume, temperature, and internal energy. These depend only on the present condition of the system, not on how it reached that condition. For example, the temperature of water remains the same whether it is heated slowly or quickly.

• Path functions include heat and work. These depend on how the process occurs. For example, compressing a gas quickly or slowly changes the amount of work done because the process path is different.

• Understanding state functions helps students calculate energy changes directly without knowing every step of the process, making problem-solving simpler.

• Recognising path functions allows students to identify how heat and work vary in different conditions and to apply the right formulas in NEET questions.

• Overall, identifying whether a quantity is a state or path function helps students approach thermodynamic questions logically and accurately.

Extensive and Intensive Properties

Properties of matter are divided into two types: extensive and intensive. Extensive properties depend on how much matter is present. On the other hand, intensive properties stay the same without depending on the size of the system.

Extensive properties include mass, volume, and total energy. These properties change when the amount of substance changes. For example, if the amount of water is doubled, its mass and volume also double.

• Intensive properties include temperature, pressure, and density. These stay the same even if the system size changes. For example, the temperature of water remains constant whether there is one litre or two litres of it.

• Understanding extensive properties helps students calculate the total energy or material needed in chemical reactions. It also allows scaling results when the amount of substance changes.

• Recognising intensive properties helps compare systems and understand their conditions. These properties are important when studying equilibrium, phase changes, and reaction rates.

• Identifying both types correctly helps students solve thermodynamics questions more confidently and analyse how changes in amount affect different physical quantities.

First Law of Thermodynamics

First Law of Thermodynamics explains that energy cannot be created or destroyed. It can only change from one form to another. This means that the total energy of a system and its surroundings always remains constant.

• Energy transformation: The first law of Thermodynamics shows that energy only changes its form. For example, when heat is supplied to a gas, it can convert into work as the gas expands.

• Formula used: The equation ΔU = q-w represents the change in internal energy. Here, ΔU is the internal energy change, q is the heat added to the system, and w is the work done by the system.

• Heat and work relation: According to this relation, when heat is added, internal energy increases. When the system performs work, such as expanding gas pushing against pressure, internal energy decreases.

• Energy conservation principle: This principle states that all energy is accounted for in chemical and physical changes. Further, it helps students understand how energy moves between systems and surroundings.

• Practical application: Students can use this law to calculate the amount of heat absorbed or work done in a process. It helps NEET students in solving numerical questions on thermodynamic energy changes with better accuracy.
  
  

Enthalpy of Reaction

Enthalpy of Reaction measures the heat change at constant pressure in a system. It shows whether a reaction releases energy (exothermic) or absorbs energy (endothermic). For example, burning methane releases heat. Hence, it shows a negative enthalpy change.

The formula ΔH = H(products) - H(reactants) helps students calculate the heat change during a reaction. Further, exothermic reactions release heat, resulting in a negative ΔH, such as fuel combustion. On the contrary, endothermic reactions absorb heat. It results in positive ΔH, such as photosynthesis. Understanding enthalpy allows students to predict energy flow and determine if external energy is needed. This knowledge helps students in solving NEET problems on reaction energy efficiently. In addition, it should be noted that enthalpy concepts help NEET aspirants analyse the energy transfer and thermal behaviour of reactions.

Gibbs Free Energy

Gibbs Free Energy combines enthalpy and entropy to determine reaction spontaneity. Negative ΔG indicates a spontaneous reaction. For example, ice melting at room temperature occurs spontaneously because ΔG is negative.

The formula G = H - TS allows students to combine heat content and disorder to predict reaction feasibility. Negative ΔG shows reactions occur naturally without external energy, and positive ΔG indicates non-spontaneous reactions requiring energy. Here, zero ΔG shows an equilibrium condition where reactants and products coexist. Calculating Gibbs free energy helps aspirants predict which reactions occur under given conditions. Gibbs' energy is important for students to understand whether a reaction can proceed naturally or not.

Spontaneity Criteria

Spontaneity criteria help students determine if a reaction occurs naturally. It depends on Gibbs free energy, enthalpy, and entropy. For example, dissolving salt in water is spontaneous because entropy increases and ΔG decreases.

Reactions with ΔG < 0 happen naturally, ΔG > 0 reactions need external energy, and ΔG = 0 indicates equilibrium. Temperature, enthalpy, and entropy affect spontaneity. Understanding these spontaneity criteria helps students to predict feasible reactions and answer thermodynamics questions effectively. Furthermore, applying spontaneity criteria helps candidates analyse chemical behaviour accurately.

Thermodynamics PDF Download

Thermodynamics PDF Download provides students with a complete and easy-to-understand guide covering key concepts like State and Path Functions, Extensive and Intensive Properties, First Law of Thermodynamics, Enthalpy of Reaction, Gibbs Free Energy, and Spontaneity Criteria. Aspirants can use this PDF to revise effectively. Also, they can solve numerical problems, and strengthen conceptual understanding for NEET preparation in a structured format

Thermodynamics PDF Download