Energy Transfer and Thermodynamics - Assignment Example

Energy transfer and thermodynamics By Chemistry of Project Please answer all 20 questions, showing workings out where appropriate and use appropriate referencing 1) Discuss the four laws of thermodynamics using words, diagrams and equations where appropriate. Include a discussion on entropy and how this is related to the laws of thermodynamics. (15 Marks) The four laws of thermodynamics describe the fundamental physical measures of enery , temperature and entropy that illustrates thermodynamic systems. The laws depict how these quantities perform under diverse circumstances,in addition they tend to prohibit certain phenomena exemplified by perpetual propulsion in movement the four laws involn thermodynamics include the first law , the second law ,the third and Zeroth’s laws of thermodynanics. ZEROTH’S THERMODYNAMIC LAW. Zeroth law of thermodynamics states that if two thermodynamic systems, each exist in a state of thermal stability with a third system, at that moment, they are in thermal equilibrium with each other. The intent of Zeroth law is to allow for the the existence of an experimental parameter, the temperature, as a property of a system is illustrated in such way that systems in thermal balance with each other have ideally identical temperature. The law as avowed here is attuned with the utilization of a specific physical body, for instance a mass of gas, to match hotness of other bodies, but does not give clear justification regarding temperatures as quantites that can be deliberated upon on a scale of actual numbers. FIRST LAW The first law of thermodynamics states that energy can neither be created nor destroyed. It can only be changed from one form to another. In any procedural design, the total energy of the universe remain the same. For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system. The first law of thermodynamics can be illustrated in different ways among them: The increases in internal energy of a closed system is equal to the heat supplied to the system less work done by it. Usystem= Q-W The augment in internal energy of a blocked adiabatic system can only be the product of net work done by the system, since Q = 0. If a system has a explicit temperature, then its overall energy has three discernible components. If the system is in action as a whole, it has kinetic energy. If the system as a whole, is in an outwardly enforced force field e.g. gravitational pull, it has potential energy comparative to some allusionary points. lastly, it has internal energy, which is a essential quantity for thermodynamics. Beyond the theoretical framework of macroscopic thermodynamics, it can be elucidated as the sum of the muddled kinetic energy of microscopic movement of its ingredient atoms, and of the latent energy of relations between them. equally, the kinetic energy of microscopic movement of the elementary atoms which amplify as the systems temperature advances upwardly. The revelation of conceptsregarding internal energy is the typical unique attribute of the initial law of thermodynamics. SECOND LAW OF THERMODYNAMICS The second law of thermodynamics states that, the entropy of an isolated system that is not in equilibrium will be liable to increase over time, approachinga highest value at the equilibrium point.tus it portrays an assertion that the irreversibile nature of natural progressions, and the propensity of natural processes to pilot towards spatial consistency of matter and energy, particularly of temperature. It can be devised in diversity of remarkable and significant mechanisms. chine is impossible. This law distinguishes that in conventional thermodynamics, the definition of entropy is arrived at, only when it has attained its hold of inner thermodynamic stability.in addition it refers to multiple reversible and irreversible processes.a simplified phenomenon of irreversibility is characterized by conduction and radiation processes in heat transfer.thus the entopy and its associated variations form a fundamental framework upon which facts pertaining to viscosity , friction and chemical reactions are demystified in a wider scope. In view of the second thermodynamic law,a quotient of heat transmitted,represented by delta Q is the resultant outcome of temperatre abbreviated as T. Entropy of such a system is represented by S thus the relationship that results is Entropy is thus, a physical assessment of the absence of physical records concerning the microscopic particulars of the motion and the consequential design of a system, provided that the identity of macroscopic states is acknowledged. The law further indicates that given two macroscopically precise states of a system, there exist a measure referred to as the variation of fact entropy among them. This statistical entropy variations describes te degree of additional microscopic physical information required to spell out one of the macroscopically ascertained states,if there macroscopic sequencing of the other It is fundamental to note that entropy increasesin natural processes because their ultimate conditions always contain microscopically specific effects which are not wholly predictable based on the initial specifications of the processes. THIRD LAW OF THERMODYNAMICS. This laws states that the entropy of an ideal crystal of any unadulterated substance approaches zero as the temperature tends to absolute zero. At zero absolute temperature, the system ought to be in a condition of lowest thermal energy. This holds true provided the ideal crystals has only one state of minimum energy. Entropy is associated to the quantity of probable microstates by: Where S is stands for the system entropy, kB represents Boltzmanns constant, and Ω the numerical value of all possible microstates i.e. the atom configurations. At absolute zero 1 microstate ensues i.e. Ω=1 because the atoms are alike for a clean substance and as a result all arrangements are identical as there is only one likely grouping . A Two cylindrical metal rods of 1 meter in length, one made from aluminium and one made from iron, are heated from 20C to 90C. Given the coefficient of thermal expansion for the aluminium and iron rods are: 23.1x10-6K-1 and 11.8x10-6K-1respectively, what is the difference in length of the two rods after heating (answer in mm)? (6 Marks) For the case of aluminium; Initial temperature: 20 degrees celcius Final temperature:90 degrees celcius Initial length 1000 mm Final length? Coefficient of thermal expansion: 0.0000231 Calculation Length final –length initial = coeffitient of expansion (temperature final –temperature initial) = 0.0000231(90-20) = 0.001617mm For the case of iron Initial temperature:20 degrees celcius Final temperature; 90 degrees celcius. Initial length : 1000mm Final length….? Coefficient of expansion : 0.0000118 calculation Length final –length initial = coeffitient of expansion (temperature final –temperature initial) X = 0.000011(90-20) =0.000826mm 3) Gold has a specific heat of 0.129J/(gC). How many joules of heat energy are required to raise the temperature of 22.0g of gold from 27C to 93C? (2 Marks) Change in heat = mass* change in temperature *specific heat capacity. 22*66*0.129 = 187.308 Joules. 4) 25.0g of mercury is heated from 25C to 155C, and absorbs 455J of heat in the process. Calculate the specific heat capacity of mercury. Q = m*c*change in temperature. 455 = 25*130(c) 0.14 j/gC (2 Marks) 5) Predict whether entropy increases or decrease for the following reaction and explain why. (Do not calculate entropy): a) CaCO3(s) CaO(s) + CO2(g) Decreases entropy because it is an exothermic reaction. b) N2(g) + 3H2(g) 2NH3(g) increases entropy because it is an endothermic reaction. c) NH4NO3(s) NH4+(aq) + NO3(aq) Increases entropy- because it is an endothermic reaction. d) H2O(g) H2O(l) increases entropy-because it is an endothermic reaction. (4 Marks) 6) Explain how work and a change in energy are related. Explain how energy change and force are related. When a force maneuvers on an object traveling on some distance, work done on the object is equivalent to the force multiplied by the distance. Furthermore, when work is done on an object, its energy increases by an amount identical to the work done. It is notable that energy is required to move against a force. There are forces in nature, such as gravity, which exist devoid of converting energy. 7) Use the table of thermodynamic data to calculate S and H for the following reactions, then calculate G (at 25.0C) using the Gibbs Equation, G = H -TS. a. NaCl(s) Na+(aq) + Cl(aq) 43.9J/K G = -407.3-(25*115.5) =-3294.5kj/mol. b. 2NO(g)+O2(g) N2O4(g), -322.4J/K G =11.3-(25*355.7) = 8881.2KJ/mol c. CH4(g) + 2O2(g) CO2(g) + 2H2O(l). -243J/K G = -285.8-(25*69.91) = -2033.55KJ/mol d. 2NO2(g) N2O4(g) -175.9J/K G= 33.18 -(25*240) =-5966.82KJ/mol (12 Marks) 8) These questions test your understanding of temperature measurements and temperature scales. a. Body temperature is 37C what is this in Kelvin, Fahrenheit and Rankinescales? In Kelvin 37+273 = 310 b. What is absolute zero in Celsius, Fahrenheit and Rankine scales? In Fahrenheit Degree Fahrenheit = degree celcius*1.8+32 =98.600degree fahreinheit. Conversion of degrees celcius to rankine scale 37derees celcius = 558.27 degrees Rankine. c. The temperature of a system rises by 45C during a heating process. Express this rise in temperature in Kelvins. Converting degrees celcius to Kelvin = 45+273 = 318kelvin. (3 Marks) 9) What is Fouriers Law? Mathematically express Fouriers Law defining all the terms used within it. What is thermal conductivity? Compare the values of thermal conductivity of metals, insulating materials and gases. Why does Fouriers law have a minus sign? (10 Marks) It is a law of heat conduction that states, the time rate of heat transfer through materials is proportional to the negative gradientof the temperature and to the area, at right directions to that slope, through which the heat flows. It can be stated in two identical forms: the integral format, in which we study the quantity of energy flowing into and or out of a body as a whole, and the disparity form, in which we look at the flow rates of energy closely . Newtons law of cooling is a distinct representation of Fouriers law, whereas Ohms law is the electrical view of te law. The differential illustration of Fouriers Law of thermal conductionindicates that the local heat flux density q, is equivalent to the resultant product of thermal conductivity, k, and the negative local temperature gradient, change in -T. The heat fluctuation density is the quantity of energy that flows throughout a unit of area/unit time. where refers to local heat flux density, W·m−2 refers to materials conductivity, W·m−1·K−1, refers to temperature gradient, K·m−1. The integral format is illustrated by integrating the differential equations perttainin to tota surface S.thus, it can be shown differentially by: where, illustrates, amount of heat transmitted per unit time (in W), and is the oriented surface area constituent (in m2) At constant temperature between two ends, the heat flow speed is given as: Where, A representsthe cross-sectional surface area, is the temperature difference between the ends, is the distance between the ends. This law forms the fundamental framework of deriving the heat equation 10) Explain the Stefen-Boltzman Law. What is emissivity? What are the range of values for the emissivity of a surface? Define the terms black surface and grey surface. What role does the view factor play in determining the rate of heat transfer? What is a blackbody? (12 Marks) This is a law that states that the total energy radiated per unit surface area of a black body per unit of time i.e.the black-body irradiance, is directly proportional to the fourth power of the black bodys thermodynamic temperature T i.e absolute temperature Emissivity refers to a extent to which something like a surface radiates absorbed energy. The range of value of emissivity range from the lowest of aluminium foil that has 0.03 to ice which has 0.97. 11) A diatomic gas does 300J of work and also absorbs 2.50kJ of heat. What is the change in internal energy of the gas? 2500-300= 2200Js 11. A diatomic gas does 300j of work and also absorbs 2.50kj of heat. What is the change in internal energy of the gas? (2 marks) =5/2 *k(Boltzmann’s constant) *t 5/2*1.3806488 × 10-23 m2 kg s-2 k-1 =8.629055*10-20j 12- What is the pressure exerted by 3.6moles of an ideal gas when it occupies a volume of 12.0l at 373k? (2 marks) PV= NrT 12*p=0.0821*3.6*373 =9.187atmospheres. 13- A flashbulb of volume 2.6cm3 contains o2 gas at a pressure of 2.3atm and a temperature 26�c. How many moles of o2 does the flashbulb contain? (2 marks) 2.3*0.0000026= n *8.2057*299 no of moles = 2*10-9 moles 14- if 0.20moles of helium occupies a volume of 64.0l at a pressure of 0.15atm, what is the temperature of the gas? (2 marks) 0.15*64 = 0.2*0.0821*t t= 584.65k 15- What is the volume of 0.35moles of gas at 1.7atm of pressure and a temperature of 100k? (2 marks) 1.7*v= 0.35*0.0821*100 v=1.690L 16. ) Explain how work and a change in energy are related. Explain how energy change and force are related. (2 Marks) When a force maneuvers on an object traveling on some distance, work done on the object is equivalent to the force multiplied by the distance. Furthermore, when work is done on an object, its energy increases by an amount identical to the work done.  It is notable that energy is required to move against a force. There are forces in nature, such as gravity, which exist devoid of converting energy. 16- what is the pressure of 1.5moles of an ideal gas at a temperature of 150k and occupies a volume of 20.0l? p*20=1.5*0.0821*150 p=0.923625 atmospheres. (2 marks) 17- A 1600kg car travels at a speed of 12.5m/s. what is its kinetic energy? (2 marks) =1/2mv2 0.5*1600*12.5*12.5 =125000j 18- a bar of an unknown metal has a length of 0.975m at 45�c and a length α of 0.972m at 23�c. What is the coefficient of linear expansion? (2 marks) =change in length/change in temperature. =0.003m/22+273 coefficient =0.000101694 m/k 19- the accepted transition Reynolds number for flow in a circular pipe is: for flow through a pipe, at what velocity will this occur at 20�c for: oil flow (?oil = 861kg/m3 , oil = 0.01743ns/m2) with a diameter of 19mm; re = (ρ u2) / (μ u / l)     = ρ u l / μ     = u l / ν            laminar flow =density *velocity*diameter Convert mm to meters. 0.01743=861*0.019*v v=0.001065468m/s Water flow (water = 998kg/m3, water = 0.001003ns/m2) with a diameter of 17mm? convert mm to meters 0.001003= 998*0.017*v Re =0.000059118m/s (10 marks) 20- what is viscosity? The viscosity of a fluid refers to the measure of resistance to of any fluid to plodding deformation occasioned by stress and variability in force. What is the relationship between viscosity and intermolecular forces? The intermolecular forces refer to the forces that keep molecules in their state of equilibrium. They are responsible for the viscosity in fluids i.e. the stronger the intermolecular force, the stronger the viscosity whereas the weaker the intermolecular force the lesser the viscosity. What is the relationship between viscosity and temperature? (6 marks) Temperature weakens the intermolecular forces thus the attraction of the molecules in their structure and bonding becomes low and consequently, viscosity diminishes with any additional temperature. List of References MCCARTHY, R. (2005). The laws of thermodynamics: understanding heat and energy transfers. New York, Rosen Pub. Group. Read More