Experiment One Determination Of The Specific Heat Capacity Enthalpy And Entropy Change Of Water Objectives The Objectiv 1 (107.34 KiB) Viewed 51 times
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Experiment One Determination Of The Specific Heat Capacity Enthalpy And Entropy Change Of Water Objectives The Objectiv 2 (82.75 KiB) Viewed 51 times
EXPERIMENT ONE DETERMINATION OF THE SPECIFIC HEAT CAPACITY, ENTHALPY AND ENTROPY CHANGE OF WATER Objectives The objectives of this experiment are: (0) To determine the heat capacity of the liquid water at atmospheric pressure. (ii) ( Obtain enthalpy and entropy change of the water after boiling Background Thermodynamics is the study of energy and its transformations, of particular interest is the relationship between heat and work. One of the fundamental tools in thermo chemistry, a branch of thermodynamics, is calorimetry. Calorimetry is the measurement of heat flow. When heat is transferred to an object, the temperature of the object increases. When heat is removed from an object, the temperature of the object decreases. For a unit mass of the object, the relationship between the heat (9) that is transferred and the change in temperature (AT) is q = CAT = C (Tf - Ti) (0) The proportionality constant in the equation is called the specific heat capacity (C). The specific heat capacity is the amount of heat required to raise the temperature of the unit mass of an object or substance by one degree. The temperature changes is the difference between the final temperature (T+) and the initial temperature (T) For mass m Q = mC AT = mc (Tr-T) (ii) For a known mass of water, m, known temperatures Ti and Tt and heat flow, Q, the specific heat capacity of the water can be obtained. The rating of the kettle is given in Watts, thus we write equation (ii) as L T-T Q = mc (iii) t Properties of steam in any state can be obtained from tables and used to perform thermodynamic analyses. In this practical, the enthalpy and entropy change of water will be obtained from both steam tables and EES software and the results will be compared. Equipment • Electric kettle. • Xplorer GLX • Temperature probe Procedure 1. Note down the value atmospheric pressure in the laboratory as given by the Xplorer GLX 2. Note down the rating of the electric kettle, this should give the energy used during the experiment. 3. Fill an electric kettle of known heating capacity with known quantity of water. 4. Measure the initial temperature of the water in the kettle before switching on the kettle V O
Procedure 1. Note down the value atmospheric pressure in the laboratory as given by the Xplorer GLX. 2. Note down the rating of the electric kettle, this should give the energy used during the experiment. 3. Fill an electric kettle of known heating capacity with known quantity of water. 4. Measure the initial temperature of the water in the kettle before switching on the kettle. 5. Place the temperature probe in the kettle and switch it on and start recording data on the Xplorer GLX. 6. Stop recording data on the Xplorer GLX when the kettle goes off and record the final temperature of the water. , Results 1. Plot the graph of temperature against time for the data obtained from the experiment. 2. What is the saturation temperature of water at the measured atmospheric pressure? 3. Compare this temperature with the saturation temperature tabulated in steam tables 4. Calculate the change in temperature for the system. 5. Calculate the specific heat capacity of the water. 6. Compare the experimental value of the specific heat capacity to the theoretical value and bring out the percentage error. Discuss why there are deviations if any. 7. Using the information in (1) to (6) above, complete Tables 1.0 and 2.0 below and comment on your answers. Table 1.0. Enthalpy Saturation h (kJ/kg) temperature steam tables as obtained from h (kJ/kg) as obtained from EES software Table 2.0. Entropy change As = C*In(T/T) As - St - Si (using As = (£/:) - St (theoretical) steam tables) (using software) Si EES V O
Title of the experiment Objective: (use the one which is applicable to your experiment) To prove the principle of......... To determine the........... To test the method of calculation of To investigate......... To test the law of...... Diagram of apparatus used: No photos or internet pictures Theory: When a body is in equilibrium under the influence.... Formulae........ Procedure: Write down the you steps followed to do the experiment. Results: (if applicable) Discussion: List factors which in your opinion may have affected the experiment readings Conclusion: State whether the objective have been achieved. Example: this method of calculation has been proved acceptable. The percentage error/ difference confirms that........
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