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 the 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 employs 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 man 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 quantitatively.
The Metric System
The fundamental unit of the metric system is the metre. The millimetre 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 is the calorie.
Choose the Russian equivalents from the right column.
relationship – подвергаться
to undergo – принять во
to take into account – внимание
flask – отношение, связь
determination – измерение колба
Open the brackets choosing a suitable word. Translate the sentences into Russian.
1. (A balance, a calorimeter, a thermometer) is a device which determines the quantity, but not the quality of heat in a body. 2. If a chemist determines mass he is to employ (a flask, a thermometer, a balance). 3. (A calorimeter, a flask, a microscope) is used if a chemist must examine small samples of matter. 4. For the measurement of volumes of gases a chemist uses (burettes, pipettes, gas burettes). 5. On (the Centigrade scale, the Fahrenheit scale) the freezing point of water is 0º. 6. The unit of (volume, mass) in the metric system is the gram. 7. If a chemist must measure extremely short distance (the centimetre, the micron) is to be used.
Part B
Read and retell the text.
A
thermometer is a device which is used to determine the temperature of
a body. Two bodies of unequal size may have the same temperature; the
bigger contains more heat, but the quality of the heat in each is the
same. Thermometers take many forms, the commonest of which is the
mercury-bulb variety.