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Specific Heat

# Specific Heat - PHYSICS 215 THE SPECIFIC HEAT OF A METAL...

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1 PHYSICS 215 THE SPECIFIC HEAT OF A METAL Object: The object of this experiment is to measure the specific heat of metal using the calorimetric method. Apparatus: Metal shot Temperature Sensor DataStudio Calorimeter Bunsen burner Boiler Ring stand Triple-beam balance Sample holder 1.0 Introduction Joule established that heat and work are energies transferred between a system and its environment. Heat and work are equivalent in the sense that the change of the system is exactly the same whether you transfer heat energy to it or do an equal amount of work on it. Adding energy to the system, or removing it, changes the system’s thermal energy. What happens to a system when you change its energy? In this lab, we’ll consider two distinct possibilities: (1) the temperature of the system changes and (2) the system can undergo a phase change, such as melting or freezing. 2.0 Theory 2.1 Temperature The most familiar concept in thermodynamics is temperature. It is also one of the trickiest concepts so for now, let’s start with a very naïve definition: Temperature is what you measure with a thermometer. If you want to measure the temperature of a pot of soup, you stick a thermometer (such as a mercury thermometer) into the soup, wait a while, then look at the reading on the thermometer’s scale. This definition of temperature is what’s called an operational definition, because it tells you how to measure the quantity in question. Ok, but why does this procedure work? Well, the mercury in the thermometer expands or contracts, as temperature goes up or down. Eventually the temperature of the mercury equals the temperature of the soup, and the volume occupied by the mercury tells us what temperature is. Notice that our thermometer (and any other thermometer) relies on the following fundamental fact: When you put two objects in contact with each other, and wait long enough, they tend to come to the same temperature. This property Is so fundamental that we can take it as an alternative definition of temperature. Temperature is the thing that’s the same for two objects, after they’ve been in contact long enough. This is the theoretical definition of temperature. But this definition is extremely vague: What kind of “contact” are we talking about here? How long is “long enough”? How do we actually ascribe a numerical value to the temperature? And what if there is more than one quantity that ends up being the same for both objects?

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2 Before answering these questions, lets introduce some more terminology: After two objects have been in contact long enough, we say that they are in thermal equilibrium. The time required for a system to come to thermal equilibrium is called the relaxation time. So when you stick the mercury thermometer into the soup, you have to wait for the relaxation time before the mercury and the soup come to the same temperature. After that, the mercury is in thermal equilibrium with the soup.
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