Thermodynamics of Central Lancashire - Assignment Example

University of Central Lancashire School of Engineering FV1201 Assignment Brief Assignment Details Please answer all 12 questions, showing workings out where appropriate and use appropriate referencing. 1) Discuss the First Law of Thermodynamics using words, diagrams and equations where appropriate. The first law of thermodynamics applies the principle of conservation of energy to thermodynamics and heat processes. It states that the total energy of an isolated system is constant implying that energy can only be transformed from one form to another form but it is neither created nor destroyed. In other words, the change in the internal energy of a closed system is equivalent to the amount of heat that is supplied to the system less the amount of work the system does on the surroundings. This law is represented in an equation as follows; ΔU = Q- W Where; ΔU represents change in internal energy of the system Q represents the heat that is added to the system W represents the work that the system does on its surroundings. (5 Marks) 2) Explain the term entropy and its relationship with the laws of thermodynamics. (10 Marks) 3) Explain the term spontaneous reaction. (8 Marks) 4) Explain the terms endothermic and exothermic reactions. (8 Marks) 5) Explain the three modes of heat transfer and how they differ from each other. The three methods of heat transfer include conduction, convection and radiation. They differ from each other in that Conduction refers to the transfer of heat through solids and/or stationery fluids. This is explained by two mechanisms including lattice vibration and particle collision which are the methods through which conduction in solids occur. On the other hand, conduction of heat through stationery fluids happens through molecular collision. On the other hand, Convection refers to the transfer of heat using motion of fluids. This is where a hot surface heats the surrounding fluid and it is carried away by fluid movement and the warm fluid is replaced by cooler fluid which then draws more heat away from the heating surface until all fluid is heated. Finally, radiation differs from both convection and conduction in that radiation as a means of heat transfer does not require a medium such as solid or fluid to pass through and hence it is heat transfer through a vacuum using electromagnetic waves/photons travelling at the speed of light and emitted by any matter with temperatures above 0 degrees. In other words, radiation occurs when emitted radiation strikes another body and it gets absorbed. For instance the solar radiation that makes our skin feels warmth when it is sunny. (12 Marks) 6) Two cylindrical metal rods of 1 meter in length, one made from aluminium and one made from iron, are heated from 20°C to 181°C. Given the coefficient of thermal expansion for the aluminium and iron rods are: 23.1x10-6K-1 and 11.8x10-6K-1 respectively, what is the difference in length of the two rods after heating (answer in mm)? ΔL =α•Lo• (T-To) Where: ΔL =The amount of expansion for the metal Lo = Original length of metal To = The original temperature T = The temperature to which metal is heated α• = Coefficient of linear expansion In this case, Aluminium metal rod Lo = 1 meter To = 20°C T = 181°C α• = 23.1x10-6K-1 Thus, Aluminium expands by; ΔL =α•Lo• (T-To) = 23.1x10-6K-1* 1(181°C -20°C) = 0.00000231*1* 161 = 0.000372meters =0.372 millimetres On the other hand, Iron expands by; ΔL =α•Lo• (T-To) =11.8x10-6K-1*1(181°C -20°C) =0.00019 meters =0.190 millimeters Difference in the length of the two rods will thus be given by increase in length of Aluminium minus increase in length of Iron = 0.372 millimetres -0.190 millimeters =0.182mm 7) Gold has a specific heat of 0.129J/(g°C). How many joules of heat energy are required to raise the temperature of 42.0g of gold from 23°C to 242°C? (2 Marks) Q =mcΔT Where: Q = Energy transferred (joules) m = mass of water c= specific heat capacity ΔT = change in temperature Q = 42.0g* 0.129J/ (/ (g°C)*219 Q =1.187× 103J 8) 25.0g of mercury is heated from 25°C to 155°C, and absorbs 455J of heat in the process. Calculate the specific heat capacity of mercury. (2 Marks) Q =mcΔT Where: Q = Energy transferred (joules) m = mass of water c= specific heat capacity ΔT = change in temperature 455 = 25.0g *c (155 -25) 455 = 25*130c 455 = 3,250c c =455/3,250 c =0.14J/goC 9) Calculate entropy ΔS, enthalpy ΔH and Gibbs Free Energy ΔG for the following equations: i) entropy a) CaCO3(s) → CaO(s) + CO2(g) ∆so =(1mol)(∆so for CaO(s)+(1mol)(∆so for CO2(g)- (1mol)(∆so for CaCo3(S) =39.8J/mol K + 213.7J/mol K -92.9J/mol K =160J/K b) N2(g) + 3H2(g) ↔2NH3(g) ∆so = (2mol) (∆so for NH3 (g)- (1mol) (∆so for N2 (g) + (3 mol) (∆so for H2(g) =2(192.78) - (191.5J/mol) + 3(130.6J/mol)) =-197.74J/K c) NH4NO3(s) → NH4+(aq) + NO3¯(aq) d) ∆so = (1mol) (∆so for NH4NO3 (g)- (1mol) (∆so for NH4+(aq) + (3 mol) (∆so for NO3¯(aq) = 113.39J/mol+ 146.44J/mol -151.08Jmol = 108.75 J/K e) H2O(g) ↔ H2O(l) ∆so = (1mol) (∆so for H20 (g)- (1mol) (∆so for H20(l) = 188.7J/mol -69.9J/mol = 118.8 J/K ii) Enthalpy a) Cao(s) + CO2(g) → CaCO3(s) 1∆Hf(CaO(S) + 1∆Sf (CO2(g)) - –(1∆Sf(CaCO3(s)) =-635.09+ -393.50 --1206.9 =-178.31kj b) N2(g) + 3H2(g) ↔2NH3(g) 1∆Hf(N2(S) + 3∆Sf (H2(g)) - –(2∆Sf(NH3(s)) =-945+ -1308 –2034 = 219kj c) NH4NO3(s) → NH4+(aq) + NO3¯(aq) (24 Marks) (1∆Hf(NH4 +1(aq) + 1∆Sf (NO3-1 (aq)) –(1∆Sf (NH4NO3(s)) = -132.51+-207.36--365.56 =-25.69kj d) H2O(g) ↔ H2O(l) 1∆Hf(H20(g)) + 1∆Sf (H2O(l)) =685 -920 = -235kj Gibbs free energy ΔG a) Cao(s) + CO2(g) → CaCO3(s) = 1ΔGf (CaO(s)) + 1ΔGf(CO2 )(g) - 1ΔGf(CaCO3) (s) = (603.5 +137.2)- -1128 = +130.9 kj b) N2(g) + 3H2(g) ↔2NH3(g) = 1ΔGf (N2 (g) + 3ΔGf (H2 (g) - 1ΔGf (NH3 (g)) =- 191.6+- 392.1-- 385.6 =198.1kj c) 1ΔGf(NH4+1 (aq)) + 1ΔGf(NO3-1 (aq))- [1ΔGf(NH4NO3 (s)) -79.37+-111.34- -184.01 =6.7kj 10) Explain how work and a change in energy are related. Explain how energy change and force are related. Change in energy and work are related in that energy is the ability to do work with the work done on an object giving the object potential or kinetic energy. In other words, work is the transfer of energy by a force that is acting on an object as it gets displaced. In other word, change in energy can simply be said to be work or to result in work and hence that is the relationship between work and energy. On the other hand, energy change and force are related in that force is something that changes a system’s energy by doing work on the energy. In other words, work is defined by a spatial integral over the force that acts on an object. In other words, it is force that causes change in energy and hence results in work being done. (5 Marks) 11) Predict whether entropy increases or decrease for the following equations, include your reasoning. NOTE: DO NOT calculate the value for entropy. a. NaCl(s) → Na+(aq) + Cl¯(aq) b. 2NO(g)+O2(g) → N2O4(g) c. CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) d. 2NO2(g) ↔ N2O4(g) (8 Marks) 12) Explain the Stefan-Boltzmann Law. What is emissivity? What is 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? The law of Stefan-Boltzmann states that the thermal energy that is radiated by a blackbody radiator or surface per second and per unit area is always proportional to the fourth power of the absolute temperature. This is given by the following equation; E = σ T4 (10 Marks) Where; E is the radiant heat energy that a unit area of the surface emits T is the absolute temperature in degrees kelvin and σ represents the constant of proportionality or the Stefan-Boltzmann constant and is valued at 5.67.4× 10-8 watt per meter 2.K4. It is worth noting that the law applies only for black surfaces. Emissivity is simply defined as the measure of the ability of an object to emit infrared energy which in turn indicates the object’s temperature. Objects emissivity range from 0 for a shiny mirror to 1.0 for a black body. It is worth noting that most organic painted and or oxidized surfaces have their emissivity values being close to 0.95. A black surface refers to a surface whose absorptivity equals 1 (α = 1). In other words, where the entire radiation incident on a surface is absorbed and hence there is neither reflected or transmitted radiation, this is called a black surface or a black body. On the other hand, a grey surface refers to a surface whose absorptivity is less than 1 (α < 1) View factor can simply be defined as the proportion of the radiation leaving surface A which eventually strikes surface B. This is useful in radiation analysis since it allows one to express the fraction of radiation that leaves a surface and strikes another surface based on the orientation of the two surfaces with relation to each other. This is based on the assumption that the radiation that a surface will receive from a source is directly related to the angle the surface subtends when viewed from the source. Black body means an opaque object emitting thermal radiation. It is worth noting that a black body is the one which absorbs all incoming light without reflecting any. The object appears perfectly black at room temperature and this is the reason behind its being called a blackbody. In solving exercises, use and indicate proper units for dimensional parameters; do not use numerical values with extra digital places. Remember: You must answer the questions set You must demonstrate that you have met the learning outcomes As you construct and present your answers, consider the assessment criteria Presentation Instructions It is your responsibility to ensure that your work is neatly and accurately presented. The work must be: Word-processed Single sided 1.5 or double line spaced Ariel 12 point font Justified Page numbered On A4 paper Margins left and right 3cm Attached to a cover sheet. Marks may be deducted for failure to follow these instructions. Please look at the Student Guide to Assessment for more information. Referencing All academic writing must be referenced. If you use other people’s ideas without referencing them you are plagiarising their work. Either: Use the Harvard system of referencing within your text. This will take the form: surname, year of publication, page number, and is enclosed within brackets, for example (Bradley 1998, 277). At the end of your work you should provide an alphabetical list of all the works you cite. Or: Use the Numeric System of referencing within your text. At every point in the text where a reference is made, insert a number (in brackets or superscript) and then list the references numerically at the end of your work, Plagiarism The use of work produced for another purpose by you, working alone or with others, must be acknowledged. Copying from the works of another person (including Internet sources) constitutes plagiarism, which is an offence within the University’s regulations. Brief quotations from the published or unpublished works of another person, suitably attributed, are acceptable. You must always use your own words except when using properly referenced quotations. You are advised when taking notes from books or other sources to make notes in your own words, in a selective and critical way. Submission Your work must be submitted with a front cover sheet (detailing the module code and title, coursework title, module name and student name, word count, date submitted). The assignment should be submitted electronically before 12.00 noon on the given date via Turnitin (a guide to submitting work via Turnitin can be found on Blackboard). The deadline for submission is 12.00 noon on 11th December 2015 Every attempt will be made to ensure that the work will be marked and available for collection by 11th January 2016. The assignment is worth 40% of the total module assessment. Learning outcomes This assessment will test your ability to meet the learning outcomes as described in your module booklet, specifically: 1. Demonstrate an understanding of the laws of thermodynamics and their applications 2. Demonstrate and understanding of the thermodynamic concepts: entropy and enthalpy and spontaneous reactions 5. Demonstrate an understanding of the basic principles of heat transfer: conduction, convection and radiation Assessment Criteria For more information please see the example marking guide at Appendix 1 Appendix 1 School of Engineering Assessment Criteria/Marking Proforma Name......................................................... Module................................ General Criteria In grading your work we will be assessing the extent to which it matches the criteria attached. The criteria are not of equal importance, but it is not possible to ascribe an exact weighting to each. What follows is intended as a general guide to the standards. 1. Severe weakness in understanding the issues/arguments/theory is likely to result in a mark of less than 40%. 2. Thorough coverage of the relevant material, with statements supported by data, evidence, literature or examples, is necessary to gain 52% or above. 3. Work which is disorganised with points randomly ordered is unlikely to gain more than 48%. 4. A logical, well-explained argument, combined with other good characteristics is usually necessary to obtain 75%. 5. Fluent grammatical expression is important for expressing ideas clearly. Errors in this area are likely to lead to a reduction in marks. General Comments: Overall Grade Markers Signature………………….Moderation Signature…………... Academic Level 4 Student…………………………………………… Classification Grade Relevance Knowledge Analysis Argument & Structure Originality Presentation 25% 25% 5% 20% 5% 20% Outstanding 75 – 100% Directly relevant to title. Able to address the implications, assumptions and nuances of the title Relevance to practice is thoroughly and explicitly addressed. Makes good use of ample knowledge of a fair range of relevant theoretical and practice related material, with evidence of an appreciation of its significance. Good analytical treatment, with occasional descriptive or narrative passages that lack clear analytical purpose. Conclusions are clear. Coherent and logically structured. Issues at stake clear. Sound work that expresses a personal position, often in broad terms. Relevance to practice is barely considered or not at all Competently written with only minor lapses from standard syntax and spelling. Style is readable with acceptable and error free format and bibliographical apparatus. Good 64-74% Directly relevant to title. Is able to demonstrate effective practice relevance. Good knowledge of a fair range of relevant theoretical and practice related material. Intermittent evidence of an appreciation of its significance. Intermittent evidence of adequate analytical ability. Some description and narrative but still able to draw clear and logical conclusions in the main. Generally coherent and logically constructed. Issues at stake generally clear. Generally sound work which expresses a personal position, often in broad terms and tends towards uncritical conformity to one or more standard views of the topic. Generally competent writing. Intermittent lapses from standard syntax and spelling. Presentation is generally acceptable and error free as is the format and bibliographical apparatus. Above Average 57-63% Generally addresses the title, sometimes addresses irrelevant issues. Relevance to practice effectively addressed, may be implicit in places. Basic understanding of a fair range of relevant theoretical and practice related material with evidence of deeper knowledge in places. Intermittent evidence of an appreciation of its significance. Some evidence of analytical ability. Intermittent passages of descriptive/ narrative material that lack clear analytical purpose. Some evidence of ability to make comparisons/ draw logical conclusions. Adequate attempt to construct a coherent argument, but may suffer loss of focus and consistency. Issues at stake may lack clarity. Largely derivative. Attempts to present a personal view, but only in broad terms. Is largely uncritical and conforms to one or more standard views. Generally competent writing. Lapses in spelling and syntax may occasionally lead to clumsy phrasing. Format and bibliography is error free and acceptable. Average 50-56% Generally addresses the title, sometimes addresses irrelevant issues. Demonstrates the ability to consider issues effectively, although does not always do so. Relevance to practice is addressed, but may be implicit in places. Basic understanding of a fair range of relevant theoretical and practice related material. Limited evidence of an appreciation of its significance. Largely descriptive or narrative in style with limited evidence of analytical ability. Some evidence of ability to make comparisons. Conclusions are not always clear and logical. Reasonable to attempt to construct an argument is evident. Occasionally lacks clarity and coherence. Partly derivative, No personal view is adequately formulated. Generally uncritical and conforming to one or more standard views. Generally competent writing although intermittent lapses from standard syntax and spelling and pose occasional obstacles for the reader. Format and bibliography is generally error free and acceptable. Below Average 41-49% Some degree of irrelevance to the title. Superficial consideration of the issues. Relevance to practice tends towards superficiality and largely implicit. Basic understanding of a limited range of relevant theoretical and practice related material. No evidence of an appreciation of its significance Heavy dependence on description and/or narrative. Paraphrase is common. Ability to make comparisons is poor. Clear and logical conclusions are sparse. Some attempt to construct an argument is evident but it lacks in sufficient clarity and coherence. Issues at stake are only vaguely stated. Almost wholly derivative. The writer’s contribution rarely goes beyond simplifying paraphrase. Little evidence of personal thought. Wholly uncritical and conforming to one or more standard views. Style of presentation, syntax, spelling and format all pose obstacles for the reader. Nevertheless, meaning is clear and bibliographical apparatus acceptable. Bare Pass 40% Some significant degree of irrelevance to the title is common. Only the most obvious issues are addressed at a superficial level and in unchallenging terms. Relevance to practice is superficially addressed and rarely made explicit. A limited understanding of a narrow range of relevant theoretical and practice related material. Clearly lacks awareness of the significance of knowledge. Barely adequate description and/or narrative. Extensive use of paraphrase which is occasionally inaccurate. Evidence of ability to make comparisons is minimal. A basic argument is evident but tends to be supported by assertion and lacks proper development. Coherence and clarity are evident only intermittently. Virtually all derivative. No evidence of personal thought. The writer’s contribution confined to paraphrase and quote. Uncritical and conforming to one or more standard views. Style of presentation makes reading difficult. Deficiencies in spelling, syntax of format impact significantly upon clarity. Bibliographical apparatus is acceptable. Fail 0-39% Relevance to the title is intermittent or missing. The topic is reduced to its vaguest and least challenging terms. Relevance to practice is barely considered or not at all. Lack of basic knowledge in either or both theory and practice necessary for an understanding of the topic. Inadequate and/or often inaccurate description and paraphrase. No evidence of ability to make comparisons or draw conclusions. Little evidence of coherent argument. There is a lack of development and the work may be repetitive and/or thin. No evidence of personal thought. Cursory paraphrase or quotation of others. Poorly written with numerous deficiencies in syntax, spelling, expression and presentation. The writer may achieve clarity (if at all) only by using simplistic or repetitious style. Bibliographical apparatus is unacceptable. Read More