Physics 2 PDF

PHYSICS 2 JEROME DUA WABINGGA, LPT What is/are the differences of microscopic and macroscopic perspective of thermodynamics? Thermodynamics: Macroscopic Perspective Learning objectives: a. Describe the macroscopic quantities of thermodynamics. b. Solve pro...

PHYSICS 2 JEROME DUA WABINGGA, LPT What is/are the differences of microscopic and macroscopic perspective of thermodynamics? Thermodynamics: Macroscopic Perspective Learning objectives: a. Describe the macroscopic quantities of thermodynamics. b. Solve problem on the different macroscopic quantities of thermodynamics.  Macroscopic Approach This approach in thermodynamics primarily focuses on collective, larger-scale properties of a system that are directly measurable, such as pressure, volume, temperature, and amount of substance. 5  Pressure In thermodynamics, pressure is defined as the force exerted per unit area on the surface of an object. It is a scalar quantity, typically measured in units such as pascals (Pa), atmospheres (atm), or pounds per square inch (psi). Pressure plays a crucial role in the study of thermodynamic systems, especially in understanding the behavior of gases and fluids. 6 Formula 7 Types of Pressure Absolute Pressure: The total pressure exerted on a system, including atmospheric pressure. Gauge Pressure: The pressure relative to atmospheric pressure. Gauge pressure can be positive (when the measured pressure is above atmospheric pressure) or negative (when it is below atmospheric pressure). Differential Pressure: The difference in pressure between two points. 8 9 Pressure is an essential parameter in various thermodynamic processes such as isobaric (constant pressure), isochoric (constant volume), isothermal (constant temperature), and adiabatic (no heat exchange). Understanding pressure and its implications in thermodynamics is crucial for analyzing and designing systems such as engines, refrigerators, and other devices that involve fluid dynamics and heat transfer. 10  Sample Problems A gas cylinder contains 2 moles of an ideal gas at a temperature of 300 K. The volume of the gas is 0.05 m³. Calculate the pressure of the gas inside the cylinder. Solution 11  A sealed container with a fixed volume contains a gas at an initial temperature of 350 K and a pressure of 1.5 atm. If the temperature is increased to 450 K, what will be the new pressure of the gas, assuming the volume remains constant? Solution 12  A water column is 10 meters high. Calculate the pressure at the bottom of the column due to the water alone. Assume the density of water is 1000 kg/m3 and the acceleration due to gravity is 9.8 m/s 2. Solution 13  Volume In thermodynamics, volume is a measure of the amount of space that a substance (solid, liquid, or gas) occupies. It is a fundamental property that is essential in describing the state and behavior of thermodynamic systems. Volume is typically measured in units such as cubic meters (m³), liters (L), or cubic centimeters (cm³). 14  Volume (V) is the amount of three-dimensional space enclosed by a boundary or occupied by an object. The SI unit of volume is the cubic meter (m³). Other commonly used units include liters (L), where 1 L = 0.001 m³, and cubic centimeters (cm³), where 1 cm³ = 0.000001 m³. 15 Phases of Volume Solids: Solids have a fixed volume that does not change significantly with changes in pressure or temperature. Liquids: Liquids have a fixed volume but can change slightly with changes in temperature and pressure. Gases: Gases do not have a fixed volume and will expand to fill the container they are in. The volume of a gas is highly dependent on pressure and temperature, described by the ideal gas law. 16 Volumetric Processes in Thermodynamics Isochoric Process: A thermodynamic process at constant volume. In such a process, the volume does not change, which implies Δ𝑉=0ΔV=0. Isobaric Process: A thermodynamic process at constant pressure. During this process, the volume can change as the temperature changes. Isothermal Process: A process at constant temperature. For an ideal gas, the product of pressure and volume remains constant. Adiabatic Process: A process with no heat exchange with the surroundings. The volume can change, but the process is characterized by changes in pressure and temperature without heat transfer. 17 The work done by or on a system can be related to changes in volume, especially in the context of gases. The work done during a volume change at constant pressure is given by: Understanding volume and its relationship with other thermodynamic properties is crucial for analyzing and designing systems like engines, refrigerators, and various industrial processes that involve the transfer and transformation of energy. 18  Sample Problems A container holds 3 moles of an ideal gas at a pressure of 2 atm and a temperature of 400 K. Calculate the volume of the gas. Solution 19  A balloon is initially at a temperature of 300 K and occupies a volume of 1.5 m³. If the temperature of the gas inside the balloon is increased to 450 K at constant pressure, what will be the new volume of the balloon? Solution 20  A certain amount of a substance has a mass of 4 kg and occupies a volume of 0.8 m³. Calculate the specific volume of the substance. Solution 21 Exercise: 1. A 2-liter container holds an ideal gas at a temperature of 350 K and a pressure of 3 atm. If the gas is transferred to a new container and the pressure is changed to 1 atm while the temperature is adjusted to 400 K, what is the new volume of the gas? 2. A 5-liter container holds 0.5 moles of an ideal gas at a temperature of 298 K. Calculate the pressure of the gas inside the container. 22 Temperature A measure of the average kinetic energy of the particles in a system. It reflects how hot or cold a system is and determines the direction of heat transfer between systems. 23 Temperature in Thermodynamics Kinetic Energy: Temperature is directly related to the kinetic energy of the particles in a substance. Higher temperature means particles are moving faster, and lower temperature means they are moving slower. Scales: Temperature is measured in different scales, including Celsius (°C), Fahrenheit (°F), and Kelvin (K). The Kelvin scale is the standard unit of temperature in thermodynamics, where absolute zero (0 K) is the point at which particles have minimum kinetic energy. 24 Temperature in Thermodynamics Zeroth Law of Thermodynamics: This law states that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This concept allows temperature to be defined and measured. Heat Transfer: Temperature determines the direction of heat transfer between systems. Heat flows from a body at a higher temperature to one at a lower temperature. State Function: Temperature is a state function, meaning it depends only on the current state of the system, not on how the system reached that state. 25 Equations In thermodynamics, the equation used to solve for temperature depends on the context of the problem. Here are some common equations involving temperature: 1. Ideal Gas Law The Ideal Gas Law relates temperature to pressure, volume, and the number of moles of a gas: 26 Equations 2. First Law of Thermodynamics This law relates the change in internal energy of a system to heat added and work done: 27 Equations 3. Heat Transfer (Calorimetry) The equation for heat transfer when there is no phase change is: 28 Equations 4. Adiabatic Process (For an Ideal Gas) In an adiabatic process, where no heat is exchanged, the temperature is related to pressure and volume by: 29 Sample Problems A 200 g block of copper at 150°C is placed into 500 g of water at 25°C. Assuming no heat loss to the surroundings, what will be the final temperature of the system? (Specific heat of copper = 0.385 J/g°C, specific heat of water = 4.18 J/g°C) Solution 30 31 Amount of Substance It refers to the quantity of entities (such as atoms, molecules, or ions) present in a system. It is a fundamental concept used to quantify the number of particles in a given sample of matter, and it is typically measured in moles. 32 Amount of Substance in Thermodynamics Mole (mol): The mole is the standard unit for the amount of substance in the International System of Units (SI).One mole of any substance contains exactly 6.022×10^23 entities, known as Avogadro's number. This could be atoms, molecules, ions, or other particles. 33 Amount of Substance in Thermodynamics Relationship to Mass: ▪ The amount of substance is related to mass through the molar mass, which is the mass of one mole of a substance. ▪ The relationship is given by: 34 Amount of Substance in Thermodynamics Ideal Gas Law The amount of substance appears in the Ideal Gas Law: 35 Amount of Substance in Thermodynamics Use in Chemical Reactions: In stoichiometry, the amount of substance allows for the calculation of the proportions of reactants and products in a chemical reaction. Balanced chemical equations provide the mole ratio of substances involved, which is essential for predicting the amounts of reactants needed or products formed. 36 37 Exercise: 1. A 250 g piece of aluminum (specific heat capacity 𝑐=0.897 J/g°C) is heated from 25°C to 100°C. How much heat energy is required to achieve this temperature change? 2. A 5.00 L container holds oxygen gas (O₂) at a temperature of 298 K and a pressure of 2.00 atm. How many moles of oxygen gas are in the container? 38