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Measuring the specific latent heat of fusion of water (ice):
In our daily lives, heat can be found in everywhere. Cooking food heat is needed, it also makes people feel warm and produce more energy. Therefore to know the specific latent heat of fusion of water, both we need to know process of the heat was transferred and kinetic energy.The aim of this experiment was to find out the specific latent heat of fusion of water and steam. First of all, heat is a kind of energy, which transfers from one object to another because of their different temperatures. The SI unit of the specific latent heat is joule per kilogram (J kg-1). The specific latent heat of fusion which is the unit used to calculate the energy need to change unit mass of a substance from a solid into a liquid without in temperature. The equation Q=ItV=ML was used to calculate the energy needed from solid to liquid. Where Q is the heat supplied; m is the mass of the solid, L stands for the specific latent heat of fusion. However, in this process, first to be calculated the energy supplied to the heater and divided it by the mass of ice melted by the heater to find the specific latent heat of fusion of ice. Next is the specific latent heat of vaporization, which was used to calculate how much heat energy for a substance need to change units of mass from liquid into vapour without in temperature. It also defined as the equation is Q=m lv +h “where lv represents the specific latent heat of vaporization of the liquid and h is the heat lost from the ‘jacket’ in time t”. Duncan (2000: 69).
Finally, calorimeter is just a kind of equipment which uses to measure heat. There are some equations were use in the result calculation. The basic theory of the simple experiment is as above.MethodsPart.1 the specific latent heat of fusion of iceThe equipment of this experiment was two funnels and two barrels, an ammeter and a voltmeter supplied. Firstly, two funnels were filled with crushed ice, and then the heater was put in one of the funnels and left them both for five minutes.
During these, the heater reached the temperature of the ice in order to change the ice to water quickly. Next, while turned on the heater, the value of voltage and current were recorded. After recording the values, the mass of water was measured that caught from each funnel in five minutes. Finally, after getting the values of masses, voltage and current, the calculation was done.Figure 1, more ice melts in the side with the beaterPart.2 the specific latent heat of vaporization of waterFinding lv can be done using the equipment below in figure 2. First of all, put a measuring cylinder on a top pan balance and surround the cylinder with lagging. The inside aluminium metal container was measured by electronic balance and the lid keep open. After the measuring cylinder was filled with water, the power was turned on to supply. Then wait the moments until the water came back to the boil. After the water was boiling, the mass of water was recorded and the clock was started. Thirdly, the power supply was connected and the power was set to 1100w. Finally, a little of the water in cylinder was emptied to become steam and the mass of water also was recorded. The apparatus in this experiment as in figure 2.Figure 2, the boiling water in measuring cylinderResultsPart 1.
The specific latent heat of fusion of ice.Table.1 The measurement of latent heat of fusion of ice.The ice with heaterFunnel without heaterMass of cup (g)7373Mass of cup with water (g)9383Mass of water (g)2010Table.1 shows the measurement of latent heat of fusion of ice. The masses are measured by electronic balance; the current of the circuit is 1.5A and the voltage of the circuit is 6V.The error of mass: ± 1gThe error of heat: ± 10JPart.2 the specific latent heat of vaporization of water.M1 ( the boiling water)M2 ( after 3 minutes)100049Table.2 The data of the specific latent heat of vaporization of water.Table.2 shows the data of the specific latent heat of vaporization of water which is the difference of the masses of water. In the experiment, the mass of the balance is 79g; the temperature of the water is 100℃;the power of cylinder is 1100W; the time is 3 minutes. And the error of the mass is ± 1g.DiscussionThe specific latent heat of fusion of ice and the specific latent heat of vaporization of water are calculated by the measurement in the tables of result section. The calculation of the specific latent heat of fusion of ice is as follows. Heat lost by water is equal to the mass times the specific latent heat of fusion and the equation is VtI=ML, M is mass of water in difference, t stands for the time taken for heat the ice and L is the latent heat of fusion of ice. ThereforeL ==∵=2700J ∴L=2.7×105Jkg-1 and it is not very similar to the exact value of the latent heat of fusion of ice, which is 3.3×105 Jkg-1. Next part is the specific latent heat of vaporization of water. The heat gained to the water and the cylinder is equal to the work down by the circuit which is 1100W, E=W × t=M lv, which E is the energy gained to the water and the cylinder, M is mass of balance, lv represents the specific latent heat of vaporization of water. From the equation just above, therefore Lv= => and then Lv =2.5×106 Jkg-1.
It is also not very similar to the exact value of the specific latent heat of vaporization of water, which is 2.3×106 Jkg-1.According to Duncan (2000:68) “the kinetic theory sees the supply of latent heat to a melting solid as enabling the molecules to overcome sufficiently the force between them for the regular crystalline structure of the solid to be broken down. And when vaporization of a liquid occurs a large amount of energy is needed to separate the molecules and allow them to move around independently as gas molecules”.
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