Energy Transfer and Thermodynamics - Assignment Example

Heat and Thermodynamics Student’s Name Tutor’s Name Course Date Heat and Thermodynamics 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. Laws of Thermodynamics Zeroth law of thermodynamics Zeroth law describes thermal equilibrium of two bodies that are indirectly related. The Zeroth law states that two thermodynamic systems are in equilibrium if each of the body is in thermal equilibrium with another system (the third system) (Nave, 2014b). If systems A and B are in thermal equilibrium with each other and B is in thermal equilibrium with C, then A is also in thermal equilibrium with C. First law of thermodynamics The first law of thermodynamics focuses on the energy of a system. According the law the energy remains the same without alteration as it changes forms. Therefore, the first law of thermodynamics states that energy can only be transformed from one form to another, but cannot be created or destroyed (Ward, 2013). It implies the total amount of in existence is constant only being changed from one form to another. The change in internal energy of a system is equal to the energy lost or gained by the system plus the work done on the system by the environement or the work done on the environement by the system. The equation for the first law where dE=change in the internal energy of the system, q= the heat transferred in or out of the system, W=the wok done on or by the environnment Both q and W can positive or negative depending on the direction of heat and work. W will be greater than zero (W>0) when work is done on the system by the environment and less than zero (W0) when the system receives the heat and less than zero (q Read More

According to the second law, the heat released by the engine is divided into doing work and some transferred to the cold reservoir (environment). In addition, it allows for the calculation efficiency of the heat engine using the formula; In refrigerators, the law states that work (W) must be done for heat to be transferred from a cold body (QC) to a hot body (QH) (Nave, 2014a). The statement further applies to heat pumps and air conditioners. Third law of thermodynamics The law states that as the temperature of the system approaches absolute zero, the disorder in the system also increases (Nave, 2014a).

At absolute temperature, no system possesses thermal energy and heat. Mathematically, it can be expressed as; Where s=entropy (j/K), T= absolute temperature (K) At absolute zero temperature, molecules of substances are immobile and there is no disorder, no entropy. Therefore, the third law of thermodynamics provides the reference temperatures at which entropy of substances can be determined. Entropy and Laws of thermodynamics Entropy also relates to thermodynamics through its second law. Like the third law, the second law of thermodynamics can also be stated in terms of entropy.

It states that the entropy can only increase or remain constant in a cyclic process. The formula is given as; Where ∆S=entropy of a process, Q= heat absorbed, T= temperature of the process (K) 2) Two cylindrical metal rods of 1 meter in length, one made from aluminum and one made from iron, are heated from 20°C to 90°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)?

The formula for change in length after thermal expansion is given as (Nave, 2014c) Where For aluminum, For Iron, The difference in the length of the two rods after heating is by getting the difference in the increments, that is, 3) Gold has a specific heat of 0.129J/(g°C). How many joules of heat energy are required to raise the temperature of 22.0g of gold from 27°C to 93°C? Where Therefore, 4) 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. From 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) The entropy increases. There are more molecules as one is broken into two; one of which is a gas that causes more disorder in the system. b) N2(g) + 3H2(g) ↔2NH3(g) The entropy decreases. The number of molecules reduces from four to two, which reduces the disorder in the system, hence a reduction in entropy. c) NH4NO3(s) → NH4+(aq) + NO3¯(aq) The entropy increases.

The number of molecules increases and changes from solid to an acqueous state that cause more disorder. d) H2O(g) ↔ H2O(l) The entropy decreases. The water molecule changes its state from a gaseous state to a liquid state, which in turn limits disorder and so a reduced entropy. 6) Explain how work and a change in energy are related. Explain how energy change and force are related. Energy is the ability to work while work done on the body gives that body energy (potential or kinetic energy).

Force through a distance is work done while energy change is a change in the ability to do the work. 7) Use the table of thermodynamic data to calculate ΔS° and ΔH° for the following reactions, then calculate ΔG° (at 25.0°C) using the Gibbs Equation, ΔG° = ΔH° -TΔS°. a. NaCl(s) → Na+(aq) + Cl¯(aq) 43.9J/K Using the table of thermodynamic (Euler, 2006), the values of S° and ΔH° for the reactants and products are obtained. Compounds S°(J/(K.mol)) ΔHf°(KJ/mol) NaCl (s) 72.3 -411.1 Na+ (aq) 59.0 -240.1 Cl- (aq) 56.5 -167.2 The change in entropy for the reaction is calculated using the formula: (Texas A&M University, n.

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