Occult Warmth of Amalgamation and Thermal Capacity - Report Example

Heat Capacity and Latent Heat of Fusion Name Course Institution Instructor DATE Submission Date Abstract This report describes specific heat capacity and latent heat of fusion. Observable parameters including temperature and mass were used to calculate specific heat capacity of a metal container that was used. The main aim of the experiment was for familiarization with using various laboratory apparatus, accurate readings on these apparatus, calculation of values and concepts of measurement significance. The report describes the setup of the experiment; the results recorded, discussed and analyzed. Moreover, errors were analyzed and discussed. Introduction Measurement of heat capacity is an investigation of entropy in a system and allows for the investigation of basic thermodynamic properties of substances. In this experiment, the known specific heat of water will be used to find the specific heat of metallic cylinder used. Heat is defined as the transfer of energy across the boundary of a system due to a temperature difference between the system and its surroundings (Raymond, & John, 2010, pg 605). Heat energy is transferred from one body to another due to temperature differences. This process is referred to as heat exchange. One technique used to measure specific heat capacity involves heating a sample to some known temperature T­x, placing it in a vessel containing water of known mass and temperature Tw < Tx, and measuring the temperature of water after equilibrium has been reached (Raymond, & John, 2010, pg 609). This technique will be used for this case and the process of heat exchange is applied. This technique is referred to as calorimetry. Aims The experiment was designed to assist in; Reading thermometers accurately The use of various volume and weight measuring devices Taking accurate notes Calculating values and concepts of measurement significance Theory Heat Capacity Heat capacity is C of a particular substance is defined as the amount of energy needed to raise the temperature of a sample of the same substance by 10 C (Raymond, & John, 2010, pg 608). The SI unit for heat capacity is J/K. From the definition, heat energy Q raises the temperature by T. This can be represented as; Q = CT Specific heat capacity c of a substance on the other hand is the heat capacity per unit mass (Raymond, & John, 2010, pg 608). Its SI unit is J/Kg°C. Considering the specific capacity of a substance, heating a unit mass of the same substance will result to corresponding temperature change. Heat Q causing temperature change T is given by Q = mcT Where; m; mass of the substance c; specific heat capacity of the same substance in use being taken to be constant over temperature change. If a metal specimen at a high temperature is placed into a beaker of cold water, the temperature of water will rise. Taking an assumption that the temperature increase is ɵ0 C = Tmax – T­­initial then; Temperature is said to have increased by ɵ0 C. N/B: Temperature changes in Celsius ɵ0 C is equal to temperature change in Kelvin ɵ° K. The heat energy contained in the metal will be transferred to the water; assuming that heat losses to the ambient air is neglected. Heat gained Q = mwcwɵw by the water is equal to heat loss of the metal represented by Q = mmcmɵm. From observable quantities, the specific heat of the metal can be calculated from this relation. mwcwɵw = mmcmɵm Latent Heat Capacity Energy has to be supplied to a substance to change its state. This heat energy does not result to temperature increase. It is for this reason known as latent heat (David, 2010 Pg 109). The specific latent heat of fusion is the energy required to cause 1Kg of a substance to change state from solid to liquid at its melting point (David, 2010 Pg109). If Q is the quantity of heat energy transfer is required to change the phase of a mass m of a substance, the ratio Lf is given by; Lf = Q/m A known mass of ice is used to cool a known mass of water. The amount of heat required to change the state of ice to water and also raise its temperature can be calculated from the resulting temperature change. If the specific heat of water is known, the latent heat of fusion of ice can be calculated from these results. Apparatus Plastic beaker 100ml Thermometer 0 -50 °C Top loading balance Metal cylinder Ice and water Source of boiling water Experiment 1: Specific Heat capacity Procedure 1. The experiment began with measurement and record of weight of the metallic cylinder to the nearest 0.1 g. 2. The metallic cylinder was then placed into the boiling water for three minutes. During this process, a lot of care had to be observed to prevent the metallic cylinder from not touching the element of the kettle. This was to ensure that the measured temperature of water was equal to that of the metallic cylinder. At the same time when the metal was being heated up, a 100ml beaker was weighed before and after 60ml of cold water was added and recorded to the nearest 0.1g. 3. The hot metallic cylinder was then removed from boiling water and blotted with tissue. 4. It was then placed in the beaker with cold water added. Temperature of water was recorded after every two seconds until two minutes. At the same time, water inside the beaker was stirred to help the heat energy transfer from metal to the cold water. 5. The experiment was repeated to obtain a second set of results. N/B: Great care had to be taken in all these steps when using thermometer because it is fragile and very sensitive to temperature changes. Results and Discussions Metal cylinder =52.3 g Plastic beaker = 16.7 g Plastic beaker with water 60 ml =54.5 g Initial temperature of water =25 0c Time t (s) Temperature ᶱC 10 27 20 29 30 30 40 32 50 34 The specific heat capacity of the material used in making the metallic cylinder can be calculated from the formula; Q = mcT and the relation mwcwɵw = mmcmɵm mw = (54.5 -16.7)g = 37.8g cw = 4182 J/Kg/K ɵ w0 C = Tmax – T­­initial = (34 - 25)0C = 90C mm = 52.3g cm = ? ɵm = Tmax – T­­initial = (34 - 25) 0C = 90C Therefore; 37.8 ×10-3 ×4182 = cm × 52.3 × 10-3 cm = (37.8 × 4182)/ 52.3 cm = 3022.55 J/Kg/K Experiment 2: Latent Heat Capacity Procedure 1. A 100ml of beaker was weighed both before and after adding 60ml of water at room temperature. 2. The temperature of water was then measured and recorded. 3. A 20mm block of ice was then added to the water and stirred throughout the experiment. Temperature was measured and recorded until the lowest value was attained. Water was stirred until the point when temperature began to rise again after two minutes. 4. The beaker containing melted ice and water was weighed and recorded. 5. The procedure was repeated with different amounts of ice and the same results were recorded to get the second set of results. Results and Discussions Mass of ice = 9.8 g Plastic beaker =16.7 g Mass of 6o ml water in the beaker = 54.5g Mass of 60 ml beaker with ice and water = 82.4 g Initial water temp = 25 0c Time t (s) Temperature 0C 10 24 20 22 30 21 40 19 50 18 60 17 70 17 Latent heat of fusion of ice originally at 00C can be calculated from the relation Lf = Q/m Heat lost by water = Heat gained by ice Heat lost by water Q = mcwT Mass of water used m = (54.5 -16.7)g = 37.8g Cw = 4182 J/Kg/K T = (25 - 17)0C = 80C Q = 37.8 × 10-3 × 4182 × 8 = 1264.64 J Heat gained by ice Q = mcwT + mLf 1264.64J = (9.8 × 10-3 × 4182 × 17) + (9.8 × 10-3 × Lf) 9.8 × 10-3 × Lf = 1264.64 - (9.8 × 10-3 × 4182 × 17) Lf = 567.92/9.8 × 10-3 = 57.96 × 103 J/Kg Sources of Errors Sources of errors in the experiment included; Heat losses from the substance to the surrounding air Parallax errors due to poor reading measuring instruments Measurement errors that resulted from unequal distribution of heat in the liquid used Correction of Errors Errors could be avoided through several methods Heat losses could be avoided through lagging To avoid parallax errors, measurements should be taken from perpendicular point of view or use digital instruments whenever possible. Equal heat distribution could be avoided through continuous stirring as the experiment continues. As a result, these workings have been calculated to an accuracy of +/- 5% . References Raymond, A. S. & John W. J. Physics for Scientists and Engineers (6th Ed). California: Cengage Learning. 2010 ISBN 0534408427 David, S. Cambridge IGCSE Physics: Cambridge International Examinations Cambridge: Cambridge University Press, 2010. ISBN0521757738, 9780521757737 Read More