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MU PHY 182 - Heat and Thermodynamics

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PHY 182 1st Edition Lecture 4 Outline of Last Lecture I. How Energy is TransferredII. Work in Ideal-Gas ProcessesOutline of Current Lecture I. What is Heat?II. The First Law of ThermodynamicsIII. Thermal Properties of MatterCurrent LectureWhat is Heat?- Joule found that you could raise the temperature of a substance by either heating it witha flame or doing work on it (i.e. a rapidly spinning paddle wheel) and both result in the substance reaching the same final state. This led to the conclusion that heat is essentially the same as work.- Heat is transferred as a consequence of a temperature difference between two interacting objects. Larger temperature difference=more heat transferred- A thermal interaction is defined as the process by which energy is transferred via atomic-level collisions.- Heat is not a state variable, which means that it is not a property of the system.- 1 calorie is defined as the heat required to raise the temperature of 1 gram of water by 1degree Celsius- 1 Cal=1,000 calories=4,186 joules. We will be using joules as the unit of heat in our calculations.- Observing a system tells us nothing about the energy process that is happening.The First Law of Thermodynamics- An adiabatic process is one in which no heat energy is transferred between the system and the environment (Q=0, however the change in temperature is not 0)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- The first law of thermodynamics states that a change in thermal energy is equal to the work done + heat transferred. This law is a very general statement about the conservation of energy.- The thermodynamic energy model is a representation of how work and heat affect the thermal energy of a system. If work is done on the system or heat is added to the system, work is positive and energy goes into the system. If work is done by the system or heat transfers to the environment from the system, work is negative and energy is lost.- It is important to realize the difference between heat and temperature. While the two are definitely related, a change in temperature does not necessarily mean heat is transferred and vice versa.Thermal Properties of Matter- Specific heat (denoted with a lowercase c) is a quality of a substance defined as the amount of energy required to raise the temperature of 1kg of a substance by 1K.- Molar specific heat (denoted with an uppercase C) is the amounts of energy required to raise the temperature of 1 mole of a substance by 1K.- You can find Q through equations using specific heat or molar specific heat. Q=mcΔT or Q=nCΔT (m: mass, n: number of moles, ΔT: change in temperature)- A phase change is characterized by a change in thermal energy without a change in temperature.- Heat of transformation (L) is defined as the heat energy that causes 1kg of a substance to undergo a phase change (Q=ML). The value of "L" is different depending on the type of phase change that is taking


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