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THE MEASUREMENTS IN CHEMISTRY

In order to understand the quantitative relationships which exist between various kinds of matter, the chemist who is in­terested in matter and changes which it undergoes, has to mea­sure the quantities of matter with which he works, that is since mass is the measure of the quantity of matter, he is to measure mass. The measuring device the chemist is to employ in this determination should be the balance.

Since for every chemical change there is always accompanying energy change which the chemist has to take into account, the calorimeter and the thermometer have to be used.

The chemist usually employs graduated cylinders, burettes, pipettes and volumetric flasks for the measurements of volumes of liquids, and the gas burette for the measurement of volumes of gases.

The chemist employ the barometer if he has to measure the pressure. The analytical chemist and the physical chemist employ such devices as calorimeters, polarimeters, refractometers and a number of electrical devices.

If the chemist is to examine very small samples of matter, he should use a microscope. The microscope is an instrument which by the combination of lenses permits men to see objects which are too small to be seen with a naked eye; It is an instrument which is useful in many sciences and which, although more frequently used in a qualitative way, can also be used quantitavely.

 

 

THE METRIC SYSTEM

The fundamental unit of the metric system is the metre. The millimeter and centimetre are the units which the chemist uses very frequently in his work. If one is to measure extremely short distances, the micron is to be used.

The unit of mass is the gram, milligram or the kilogram.

The unit of the heat measurement is the calorie.

 

Words to be remembered:

in order to burette

quantitative flask

to undergo volumetric

relationship pressure

device sample

determination unit

balance frequently

 

 

¹9


Date: 2015-01-12; view: 161


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