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Experiment 9 - Method of Mixture

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Louise Santos

on 3 October 2012

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Transcript of Experiment 9 - Method of Mixture

Theory Results and Discussion Abstract In this experiment, the specific heat of metal (steel), the latent heat of fusion of water as well as the heat of vaporization of water was determined. Results in this experiment showed that the heat lost in the system is equal to the heat gained in the system; furthermore this concept enabled the group to determine the specific heat of steel as well as the latent heat of fusion and vaporization of water. Introduction Phase changes occur when heat is added at a constant rate until physical alterations happen to the substance.

In this experiment, the specific heat of a solid was determined by the method of mixtures; the latent heat of fusion and heat of vaporization of water were determined.



Specific heat Specific heat is the amount or quantity of heat per unit of mass of a substance required to raise its temperature to 1 degree Celsius. The following formulas were used in this experiment: Specific heat of metal Latent heat of fusion Latent heat of vaporization METHODOLOGY The empty inner vessel of the calorimeter was weighed. The vessel was filled with water, about 2/3 full. Then the inner vessel with water was weighed and was placed in its insulating jacket and its temperature was measured.

The metal object was weighed. A piece of thread was tied to it and it was put into the beaker of water. The set up was heated until the steel reached a temperature of 80 degrees Celsius.

It was quickly transferred from the beaker to the calorimeter without splashing any water. The calorimeter was covered. The equilibrium temperature was recorded. ACTIVITY 1
SPECIFIC HEAT OF METAL ACTIVITY 2
HEAT OF FUSION OF WATER The inner vessel of the calorimeter was weighed, filled half-full of water, and was weighed again. It was placed in its insulating jacket. The initial temperature of water inside the calorimeter was recorded.
Ice was put inside the covered calorimeter. The calorimeter was continuously swirled until the ice was completely melted and thermal equilibrium was established. The inner vessel with water and melted ice was weighed. The heat of fusion of ice by Conservation of Heat was computed. ACTIVITY 3
HEAT OF VAPORIZATION OF WATER The inner vessel of the calorimeter was 2/3 filled with water, and was weighed and was placed inside the jacket. The initial temperature of water inside the calorimeter was recorded. The water inside the steam generator was heated until steam came out of the tube. Steam was introduced into the calorimeter until the temperature reached 40 degrees Celsius. The steam tubing was removed from the calorimeter and the water was stirred. The inner vessel was immediately weighed with its contents. The latent heat of evaporation was computed. Based from the results, the calculated specific heat of the sample steel was 542.55 J/kgC°. This is the amount of heat that steel needs for it to be able to raise its temperature by 1°C. The percent error of the calculation in this experiment is 20.25%, mainly caused by human error: after heating, the sample steel was not immediately immersed inside the inner vessel of the calorimeter for the measurement of equilibrium temperature hence resulting to inaccurate overall temperature reading of the equilibrium temperature of sample, water, and inner vessel of calorimeter. Similar error could be avoided by being careful in preserving the temperatures of both the system (sample) and the surrounding (water inside the calorimeter) during the experiment. Based from the results, the latent heat of fusion computed was 27.1x104 J/kg. This was the energy required to turn ice into water. A 19.10% error was obtained due to the approximation that initial temperature of ice was 0°C. Also the calculated mass of ice could have been the cause of an inaccurate result. Based from the table, the calculated latent heat of vaporization was 22.6x105 J/kg. This is the energy required to change a gram of water into its gas state. A 77% error was obtained. This was due to the approximation that the temperature from the Erlenmeyer flask to the calorimeter (T2) was 100°C. Another source of error is that the steam escaped when the mass of inner vessel of calorimeter, water and condensed steam was taken. This led to a low effect on the calculated latent heat of vaporization. This could be avoided if the inner vessel of the calorimeter was covered with a cloth so that steam could not escape. Conclusion The group was able to meet the objectives of this experiment in the three activities. In activity 1, for the determination the specific heat of metal. In activity 2, for the latent heat of fusion and in activity 3 for the determination of the latent heat of vaporization with the aid of the materials and formulas designated in each. Some applications: Reference [1]www.kentchemistry.com/links/Energy/SpecificHeat.htm Is it possible to add heat to a body without changing its
temperature? Yes, it is possible. You can add heat to a body without changing its temperature. One example is that of boiling water: adding heat will only result to phase change but not to its temperature. Early in the morning when the sand in the beach is already hot, the water is still cold. But at night, the sand is cold while the water is warm. Why? Water has high specific heat capacity. It takes a slower rate to absorb or release heat compared to the sand which has lower heat capacity causing the sand to absorb and release heat at a faster rate. Explain why alcohol rub is effective in reducing fever. Latent heat of vaporization of alcohol is much lower than water so alcohol evaporates faster at lower temperature. When rubbed to a person with fever, it cools off the body by taking away body heat, evaporating alcohol away from the skin. Why is water commonly used as coolant? Water is commonly used as a coolant since it has a high heat capacity, which makes it suitable as a heat transfer medium. It can store large amounts of heat before raising its temperature.
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