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Unformatted text preview: Energy of Phase Changes Group Participants: Jason Christian , Connor Dennis, Josh Istas Section Number: 416 Meeting Time: 7:30-10:20 November 2, 2006 TA: Amanda Reeves Introduction Energy change is a result of work and change in heat. In this experiment, only heat change occurs. Heat travels down the gradient from warmer to cooler to reach equilibrium. To increase the heat of a system, energy must be added to the system. The heat of the system continues to rise as energy increases. The heat continues to rise until a phase change which also takes energy from solid to liquid, liquid to gas, or solid to gas (or visa versa). During the phase change, energy increases but temperature remains constant. Phase changes occur at a different temperature for different substances. Phase change from solid to liquid/liquid to solid is called melting (fusion)/freezing. Phase change form liquid to gas/gas to liquid is called boiling (vaporization)/condensing. Phase change form solid to gas/gas to solid is called sublimation/deposition. Heat can be calculated with the following equation: q = mst where m=mass s=specific heat.the specific heat of water = 4.184 C g J t=change in temperature H = Heat of reaction = = Weight m q Molar H in mole J If there is a change in heat on the system, q system , then the change in heat of the surrounding equals -q system . This concept can be used to find the heat of reaction of materials with unknown or uncalculated specific heat such as N 2 and CO 2 . By finding q surrounding (q water ), the change in heat of N 2 or CO 2 can be found. Experimental Part 1 First, two pairs of styrofoam cups were obtained, labeled one and two, massed, and recorded. About 250 mL of water was heated to 60C. Then, cup number one was warmed with heated water. Cup number one was then filled with about 60 mL of heated water. Cup number one was then placed inside cup number two to help keep the water insulated. The first pair of cups was massed and the mass was recorded. Next, about 20 grams of ice was added to cup number one of the second pair of cups and the pair was...
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- Spring '08