Thursday, October 7, 2010

What is Calorimetry?

Calorimetry

Calorimetry is the science of measuring heat of chemical reaction or physical changes. Calorimetry is performed with a calorimeter.The word Calorimetry is derived from the latin word "calor", meaning heat. Scottish physician and scientist Joseph Black was the founder of calorimetry.

Calorimetry has two kinds, the indirect calorimetry and direct calorimetry. Indirect calorimetry calculates heat that  living organism produce from their production of carbon dioxide and nitrogen waste while direct calorimetry it also calculates the heat that living organism produce in which the entire organism is placed inside the calorimeter for the measurement.


Calorimeter

Calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reaction or physical change as well as heat capacity. There are many types of calorimeter, some of this are scanning calorimeters, isothermal micro calorimeters, titration calorimeters and accelerated calorimeter. A simple calorimeter just consist of a thermometer attached to a metal container full of water suspended above the combustion chamber.


Specific Heat

The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The relationship between heat and temperature change is usually expressed in the form shown below where c is the specific heat. The relationship does not apply if a phase change is encountered, because the heat added or removed during a phase change does not change the temperature.


Equation:

The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation. The specific heat per gram for water is much higher than that for a metal.

On Heat Capacity:

  • The Heat Capacity itself is extensive (scales with the size of system), but we can think of making this quantity intensive (making it an intrinsic property of the material) by defining related quantities:
    • the Molar Heat Capacity is defined as the Heat Capacity of a homogeneous pure compound (or element) divided by the the number of moles of that compound (or element)
    • the Specific Heat is defined as the Heat Cpacity of a homogeneous sample divided by its mass.
  • The Heat Capacity of any substance is positive.
  • The Heat Capacity is discontinuous at phase transitions.
  • For a gas, the Heat capacity depends on how one does the heating. The Heat Capacity at constant Volume, CV, and the Heat Capacity at constant pressure, Cp, for any given substance are are almost exactly equal if the substance is a solid or a liquid.  This means that for a liquid or a solid, the heat capacity doesn't depend on how you perform the heating. Cp and CV are not equal for a gas;  Cp is always greater than CV by a constant value. For one mole of gas, the difference between Cp and CV is the constant R (R is the so called universal gas constant)  and represents the capacity of the gas to perform expansion work at constant applied pressure. {Cp = CV+R for an ideal gas}  Since, for solids and liquids, the constant pressure and constant volume Heat Capacities are the same, the subscript p or V on the 'C' is usually dropped.
  • Q = m C DT This means that the proportionality between the Heat flow into (or out of) an object and the Temperature change of that object is the total Heat Capacity, which can be expressed as a molar property or per mass.
    • if m is moles and C is molar Heat Capacity
    • if m is mass (grams) and C is the Specific Heat
    • Q is positive for a temperature increase because the system has undergone an endothermic change of state 

Note: The molar heat capacities of most metals around room temperature are all around 25 J/K.g. This is because the capacity to accommodate energy depends on the number of metal atoms. Non-metals are a little more complicated


25 comments:

  1. WOW!! I learned a lot :) thanks for the info =)

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  2. .. interesting .. :)
    ..learned something about calorimetry....:)

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  3. (: I'd like to see some pictures. Haha((:char.
    HAN(:

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  4. ayus ah..ki sir jonatz ni anu?haha

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  5. This page is not finished yet, dont worry Han:)) nwei, thankss fr yr comment. :D

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  6. thanks for the comments everyone:)) keep on commenting for a chance to win .... KNOWLEDGE! Lol

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  7. interesting.. xD
    reading this blog fascinates me..

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  8. thanks to your blog it really helps :)

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  9. so prodigenous! learned a lot
    to know more visit http://www.facebook.com/pages/Calorimetry/129995213717922 :D thank y'all

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  10. fascinating! project sa physics? AWESOME! :D thanks for the info :)

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  11. NICE...
    Thanks po sa information, may natutunan ako sa Physics.

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  12. nice...physics seems to be easy if a tool like this, is always available for students...

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  13. great site! for improvements, it would be better if there would be more sample problems with solutions. With that, it will really be helpful to students in getting additional knowledge in calorimetry. :)

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  14. it's nice.. i'd like to see some pics.. nosebleed. :)

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  15. informative kahit nosebleed. LOL :DD

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  16. haha. geek tlga si travs. PRODIGENOUS. haha, parang si Quentin sa October Sky :P keep it up!

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