Showing posts with label properties. Show all posts
Showing posts with label properties. Show all posts

Friday, January 22, 2010

Calorimetry

LinkGrand.com

the discovery of certain thermal properties of substances such as calorific value, specific heat or latent heat in physics and chemistry. The instrument used is called a calorimeter and it consists essentially of apparatus which allows the substance to be burnt and the heat transferred to a surrounding body of water, enabling the rise in temperature and therefore the heat output to be measured.

Taken from Dictionary of Science

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Calorimetry is the science of measuring the heat of chemical reactions or physical changes. Calorimetry involves the use of a calorimeter. The word calorimetry is derived from the Latin word calor, meaning heat. Scottish physician and scientist Joseph Black, who was the first to recognize the distinction between heat and temperature, is said to be the founder of calorimetry.


Indirect calorimetry calculates heat that living organisms produce from their production of carbon dioxide and nitrogen waste (frequently ammonia in aquatic organisms, or urea in terrestrial ones), OR from their consumption of oxygen. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption this way, using multiple regression. The Dynamic Energy Budget theory explains why this procedure is correct. Of course, heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.


The specific heat formula is as follows:


q = m c \Delta T \,


where


q is energy, or heat,
m is mass,
c is specific heat capacity,
ΔT is change in temperature.

Taken from Wikipedia



Sunday, January 3, 2010

Qualitative Analysis


the chemical examination of a sample to discover what substances are present.

Taken from Dictionary of Science

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In the qualitative analysis procedure, the chemical properties of an unknown substance are determined by systematically reacting the unknown with a number of different reagents. By predetermining what the particular reaction will produce if a specific ion is present, the ions that actually are in the solution can be identified. For example, if a reaction is known to produce a precipitate if ion A is present and a precipitate is formed when the reaction is run, then ion A may be present in solution (there may be, and usually are, other ions that will also precipitate with a particular reagent). If no precipitate is formed when the reaction is run, then ion A is clearly not present in the unknown solution and a different reaction will have to be run to determine what ions are present.


There are two general situations in which qualitative analysis is used - in the identification of a simple salt, or the identification of multiple cations in a solution.


Taken from Wired Chemist