lecture 1-2 - Lecture 1. The equation of state Divide the...

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Lecture 1. The equation of state Divide the world in two parts: the system and the environment (the medium). The system is in equilibrium with its environment (properties of the system and the medium do not change in time) SYSTEM environment To specify the state of the system means to provide enough information so one can recreate the system in his/her lab. How many quantities do we need to specify the state? (temperature, density, color, smell, pressure, taste, chemical composition)? Consider one-chemical (one type of molecules) one-phase (liquid, gas etc.) system. Then the state is specified by giving any 2 out of the three quantities: temperature T, pressure P, and the volume of 1 mole V = V/n. Temperature T. When two bodies are in thermal equilibrium, they have the same temperature (so we know that T 1 = T 2 although we still don’t known what T 1 or T 2 are). When two objects are brought in contact, the hotter one gets colder and the colder one gets warmer. Many materials expand when they get hotter (e.g., mercury) and this can be used to create a temperature scale. Temperature scales: degrees Celsius (centigrade): water freezes at T C = 0 and boils at T C = 100. degrees Fahrenheit: water freezes at T F =32 and boils at T F = 212 conversion: T C = 5 (T F – 32)/9
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degrees Kelvin: T K = T C + 273.15; T K is always > 0 All temperature scales that are based on some material’s property to expand with temperature are flawed because they rely on the physical properties of a specific chemical. Also, most thermometers only work in a limited range of temperatures. We can’t measure the temperature of a neutron star with a mercury thermometer. We will discuss later how to construct – at least in principle – a temperature scale that is independent of the material used to build the thermometer. From molecular theory you’ll learn that temperature is a measure of average
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This note was uploaded on 04/24/2011 for the course CH 52635 taught by Professor Makarov during the Spring '11 term at University of Texas at Austin.

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lecture 1-2 - Lecture 1. The equation of state Divide the...

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