Physical Chemistry I (TKK-2246) 13/14 Semester 2 Instructor: Rama Oktavian Office Hr.: M.13-15, Tu , W , Th , F

Outlines 1. Review 2. Thermodynamic terms 3. Heat and work 4. 1 st law of thermodynamic

Review Gas properties Properties of gas Microscopic view of a solid Properties that can be observed and measured Macroscopic properties Properties of bulk gases Observable – Pressure, volume, mass, temperature.. How to make relation between those macroscopic properties of gas?? The general form of an equation of state is p=f(T,V,n)

Review Gases Exert Pressure: What is Pressure? Pressure is defined as the force exerted divided by the area it acts over Pressure = Force/Area The SI unit of pressure, the pascal(Pa), is defined as 1 newton per metre-squared: 1 Pa =1 N m −2 1 Pa =1 kg m −1 s −2 1 atm = ×10 5 Pa exactly 1 bar =10 5 Pa

Review Pressure measurement Barometer – device that measures atmospheric pressure Invented by Evangelista Torricelli in 1643 the height of the mercury column is proportional to the external pressure

Review Pressure measurement

Review Boyle’s law Boyle’s Law is one of the laws in physics that concern the behaviour of gases When a gas is under pressure it takes up less space: The higher the pressure, the smaller the volume Boyles Law tells us about the relationship between the volume of a gas and its pressure at a constant temperature The law states that pressure is inversely proportional to the volume

Review Charles’s law Jacques Charles French chemist Jacques Charles discovered that the volume of a gas at constant pressure changes with temperature. As the temperature of the gas increases, so does its volume, and as its temperature decreases, so does its volume. The law says that at constant pressure, the volume of a fixed number of particles of gas is directly proportional to the absolute (Kelvin) temperature

Review Avogadro’s law Avogadro’s law states that  the volume of a gas is directly related to the number of moles (n) of gas  T and P are constant V 1 = V 2 n 1 n 2

Ideal Gas law The combination of those laws gives Usually written as: R is gas constant

Ideal Gas law R is known as universal gas constant Using STP conditions

Equation of state The general form of an equation of state is p=f(T,V,n) Ideal gas equation is equation of state

Equation of state P, V, n, T are properties Intensive properties – independent on the quantity of material P, T Extensive properties – dependent on the quantity of material n, V Intensive properties The ratio of any two extensive variables is always an intensive variable

Ideal gas and Real gas Ideal gas The ideal gas law was useful in determining the properties of a specific sample of gas at constant T, P, V, and n. We often need to know how a change in one (or more) properties impacts the other properties for a sample of a gas

Ideal gas and Real gas Real gas deviations from the perfect gas law because molecules interact with one another Repulsive forces are significant only when molecules are almost in contact Attractive intermolecular forces have a relatively long range and are effective over several molecular diameters

Molar mass of ideal gas Determination of molar mass for ideal gas Ideal gas equation Intensive properties and measurable

Dalton’s law Partial pressure Dalton’s law

Kinetic theory of gases Pressure and molecular speed relation (1) Where M = mN A, the molar mass of the molecules, and c is the root mean square speed of the molecules, the square root of the mean of the squares of the speeds, v, of the molecules: (2)

Kinetic theory of gases Pressure and molecular speed relation Using Boyle’s Law and ideal gas Law the root mean square speed of the molecules in a gas at a temperature T must be the higher the temperature, the higher the root mean square speed of the molecules, and, at a given temperature, heavy molecules travel more slowly than light molecules

Kinetic theory of gases Pressure and kinetic energy relation Kinetic energy of molecule is defined as M = mN A N = nN A

Kinetic theory of gases Pressure and kinetic energy relation Using Boyle’s Law and ideal gas Law k is Boltzmann constant k = × m 2 kg s -2 K -1

Condensed Phase The definition of “condensed phase” made denser, especially reduced from a gaseous to a liquid state.

Liquid properties General definition of and Volume expansivity Isothermal compressibility The value is usually small

Liquid properties General definition of and

Thermodynamic terms What is thermodynamic? the study of the transformations of energy enables us to discuss all matters quantitatively and to make useful predictions e.g: The release of energy can be used to provide heat when a fuel burns in a furnace, to produce mechanical work when a fuel burns in an engine, and to generate electrical work when a chemical reaction pumps electrons through a circuit

Thermodynamic terms A thermodynamic system is that part of the physical universe the properties of which are under investigation A system is isolated when the boundary prevents any interaction with the surroundings A system is called open when mass passes across the boundary, closed when no mass passes the boundary

Thermodynamic terms Properties of a System - physical attributes that are perceived by the senses, or are made perceptible by certain experimental methods of investigation 1. non-measurable, as the kinds of substances composing a system and the states of aggregation of its parts 2. measurable, as pressure and volume, to which a numerical value can be assigned by a direct or indirect comparison with a standard

Thermodynamic terms State of a System. A system is in a definite state when each of its properties has a definite value. Change in State, Path, Cycle, Process. Let a system undergo a change in its state from a specified initial to a specified final state The change in state is completely defined when the initial and the final states are specified The path of the change in state is defined by giving the initial state, the sequence of intermediate states arranged in the order traversed by the system, and the final state

Thermodynamic terms A process is the method of operation by means of which a change in state is effected State Variable,.... A state variable is one that has a definite value when the state of a system is specified.... Path Variable,… Variable that do depend on path

Heat, work, and energy Work (W) - any quantity that flows across the boundary of a system during a change in its state Ex: - gas that pushes out a piston and raises a weight - A chemical reaction that drives an electric current through a resistance also does work

Heat, work, and energy Heat ( Q) - any quantity that flows across the boundary of a system as a result of a temperature difference between the system and its surroundings The internal energy (U) of a system is identified with the random, disordered motion of molecules. The internal energy is a state function

Heat, work, and energy Consider a system consisting of 10 g of liquid water contained in an open beaker under constant pressure of 1 atm. Initially the water is at 25 °C the initial state : p = 1 atm, t = 25 °C The system is contacted with 100 g of water at a high temperature, 90 °C. The system is kept in contact with this 100 g of water until the temperature of the 100 g has fallen to 89 °C The final state of the system is described by p = 1 atm, t = 35 °C and heat flows from surrounding into the system

Heat, work, and energy Change of state due to work Initial state : 10 g of water, p = 1 atm, t = 25 °C Then the final state is p = 1 atm, t = 35 °C There was no heat flow, but there was a flow of work

Heat, work, and energy Heat and work are called path functions

1 st law of thermodynamics The internal energy of an isolated system is constant heat and work are equivalent ways of changing a system’s internal energy. The 1st Law of Thermodyamics simply states that energy can be neither created nor destroyed (conservation of energy)

1 st law of thermodynamics Mathematical statement for The 1st Law of Thermodyamics ΔU = q + w in which w > 0 or q > 0 if energy is transferred to the system as work or heat and w < 0 or q < 0 if energy is lost from the system as work or heat

1 st law of thermodynamics

Consider the combustion process that occurs in the cylinder of an automobile: 2C 8 H 18 (l) + 25O 2 (g)  16CO 2 (g) + 18H 2 O(g) because the reaction produces a greater amount of gas than is consumed, the reaction pushes the piston upward against the force of gravity and the tension of the camshaft. The point is that this process involves some work Define: What is the system and surroundings, the sign of heat and work