Figure 1 shows the temperature dependence of magnetization in Gd5Si2Ge2 compound at and at atmospheric pressure. Open symbols are the experimental data and the solid symbols represent the theoretical curve. The circles are for sample heating and triangles are for sample cooling. The value of saturation magnetization at 8 K in the theoretical curve was normalized with the experimental data. The values of and were adjusted according to the critical temperatures from the M vs. T curves (Fig. 1) at atmospheric pressure for sample heating and cooling (table 1). It is worth noticing that fixes the Curie temperature and is responsible for the existence of first order magnetic phase transition and fixes the thermal hysteresis of about 5 K.
Table 1 shows the values of our model parameters adjusted to fit the experimental data for the pressures 1.5, 2.0 and 2.9 kbar. Values of model parameters used in the theoretical curves adjusted at zero magnetic field.
Figure 2 shows the isothermal entropy changes heating the sample (a), (b) and (c) and (the figure 3 cooling the sample (a), (b) and (c)). The solid curves are due to the variations from atmospheric pressure (P^at) to applied pressure, P=1.5 kbar (fig.2a and fig.3a), P=2.0 kbar (fig.2b and fig.3b), P=2.9 kbar (fig.2c and fig.3c) without applied magnetic field (µ_0 h_0=0 T) for sample heating and cooling, as indicated by the arrows. The open circles and open squares represent 〖ΔS〗_T vs. T experimental data for Gd5Si2Ge2 which are in good agreement with our theoretical curves for sample heating and cooling, respectively [19]. The value was used for this compound in our theoretical curves [28], value that we kept in our model in all theoretical curves. For all pressure changes, th...
... middle of paper ...
...ing applied pressure, in fact only the 〖ΔS〗_T-peak intensity increases with increasing pressure. We predict an increase in the 〖ΔS〗_T-peak intensity on average of 58% compared to 〖ΔS〗_T-peak intensity for P^at→P (at zero applied magnetic field). The open symbol show 〖ΔS〗_T vs. T for variation of pressure (P^at→P) keeping the fixed applied field (µ_0 h_(0 (fixed))=5 T), for sample heating (triangles) and cooling (inverted triangles), respectively. That intensity of the applied field, each applied pressure P=1.5,2.0 and 2.9 kbar it is provided that the phase change occurs in T=289.0,289.1 and 289.4 K, and that the intensity of the peaks are 〖ΔS〗_T=-2.3,-3.4 e -3.9 J/kg.K, respectively. The reduction in the peak intensities of 〖ΔS〗_T can be ascribe to the loss of first order phase transition (at µ_0 h_(0 (fixed))=5 T) once we notice the loss of thermal hysteresis.
Physical Chemistry Laboratory Manual, Physical Chemistry Laboratory, Department of Chemistry, University of Kentucky, Spring 2006.
The nano-thermal analysis method is capable of studying the specific regions of a sample irrespective of its composition. In a multi-component sample, the analysis methods make it possible for the researchers to distinguish between the different components and identify the different characteristics found in each of the sample (Craig, 2002). During the analysis of any sample, the nano-thermal method does not necessarily require the physical alteration of the sample. In its place, it is capable of analyzing any sample through surface studies.
Gadolinium and its performance were limited by the use of passive regenerators and heat exchangers in the refrigeration cycle [25]. So, a magnetic refrigeration device must utilize a regenerative process to produce a large enough temperature span to be useful for refrigeration purposes [26].
2. Liang Chi Shen and Jin Au Kong, Applied Electromagnetism, 3rd ed. PWS Publishing Company, 1995.
The data which was collected in Procedure A was able to produce a relatively straight line. Even though this did have few straying points, there was a positive correlation. This lab was able to support Newton’s Law of Heating and Cooling.
The molar specific heats of most solids at room temperature and above are nearly constant, in agreement with the Law of Dulong and Petit. At lower temperatures the specific heats drop as quantum processes become significant. The Einstein-Debye model of specific heat describes the low temperature behavior.
I carried out each experiment for each alcohol twice, to be more accurate in my results. GRAPH Conclusion I can now conclude that the prediction I made before the experiment is correct. In my prediction I said that the amount of heat produced per gram would increase as the number of chemical bonds in alcohol increases. This statement turned out to be true. As you can see from my graph, Propanol had the highest amount of heat produced, and this also had the highest number of chemical bonds.
The objective of this experiment was to identify a metal based on its specific heat using calorimetry. The unknown metals specific heat was measured in two different settings, room temperature water and cold water. Using two different temperatures of water would prove that the specific heat remained constant. The heated metal was placed into the two different water temperatures during two separate trials, and then the measurements were recorded. Through the measurements taken and plugged into the equation, two specific heats were found. Taking the two specific heats and averaging them, it was then that
This question refers to the example data given below. Using the rate law and the experimental values given below, calculate k.
The temperature probe was placed into the test tube and recorded the temperature of the freezing solution using Logger Pro software. The test tube was held against the inner glass of the ice bath beaker so the test tube was visible to see when the solution froze over. Once the freezing point was measured, the temperature stopped being monitored and the data was recorded. The steps mentioned above for finding the freezing point, also known as ΔTf, was replicated for the 0.0, 0.4, and 0.6 concentrations. To find the freezing point depression, the equation ΔTf = imKf was used. The molality (m) of each solution was then calculated dividing moles of solute by kilograms of solvent, and the Kf value for magnesium chloride is known to be -1.86. Since magnesium chloride breaks down into three ions in deionized water, it was concluded that the Van’t Hoff factor couldn’t exceed three. For better accuracy, the experiment explained above for finding the freezing point depression and Van’t Hoff factor was re-conducted exactly the same to determine more accurate results. Again, the molality of each solution was calculated, and a graph expressing the change in freezing temperature verses molality
Mann, M., 2013. Mind Action Series Physical Sciences 12 Textbook and Workbook. Sanlamhof: Allcopy Publishers.
As discussed in class, submission of your solutions to this exam will indicate that you have not communicated with others concerning this exam. You may use reference texts and other information at your disposal. Do all problems separately on clean white standard 8.5” X 11” photocopier paper (no notebook paper or scratch paper). Write on only one side of the paper (I don’t do double sided). Staple the entire solution set in the upper left hand corner (no binders or clips). Don’t turn in pages where you have scratched out or erased excessively, re-write the pages cleanly and neatly. All problems are equally weighted. Assume we are working with “normal” pressures and temperatures with ideal gases unless noted otherwise. Make sure you list all assumptions that you use (symmetry, isotropy, binomial expansion, etc.).
The development of superconductors has been a working progress for many years and some superconductors are already in use, but there is always room for improvement. In 1911, Dutch physicist Heike Kamerlingh Onnes first discovered superconductivity when he cooled mercury to 4 degrees K (-452.47º F / -269.15º C). At this temperature, mercury’s resistance to electricity seemed to disappear. Hence, it was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. Later, in 1933 Walter Meissner and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field. A magnet moving by a conductor induces currents in the conductor, which is the principle upon which the electric generator operates. However, in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material - causing the magnet to be repulsed- known today as the “Meissner effect.” The Meissner effect is so strong that a magnet can actually be levitated over a superconductive material, which increases the use of superconductors. After many other superconducting elements, compounds, and theories related to superconductivity were developed or discovered a great breakthrough was made. In 1986, Alex Muller and Georg Bednorz invented a ceramic substance which superconducted at the highest temperature then known: 30 K (-243.15º C). This discovery was remarkable because ceramics are normally insulators – they do not conduct electricity well. Since their discovery the highest temperature for superconductivity to occur is 138 K (-130.15º C).
Temperature has a large effect on particles. Heat makes particles energized causing them to spread out and bounce around. Inversely the cold causes particles to clump together and become denser. These changes greatly F magnetic the state of substances and can also influence the strength of magnetic fields. This is because it can alter the flow of electrons through the magnet.