II. 



MATTEE. 



Matter occupies space, resists being put in 

 motion, and is unable to part with its motion except 

 by communicating it to other matter. 



About seventy simple substances are known to the 

 chemist. A simple substance, or element, is one 

 that cannot be separated into two or more different 

 kinds of matter; for example, gold, silver, mercury, 

 iron and sulphur are elements. Elements are divided 

 into metals and non-metallic substances, most of them 

 being classed among the former. 



At ordinary temperatures elements exist as gases, 

 liquids or solids. Four, namely, hydrogen, oxygen, 

 nitrogen, and chlorine, are gases, while bromme and 

 mercury are the only liquid elements, all the others 

 being solids under ordinary conditions. It is proba- 

 ble that fluorine also is a gas. 



Any substance may be a solid, a liquid, or a gas, 

 depending on the temperature and pressure to which 

 it is subjected. 



All ordinary gases, both simple and compound, 

 have been liquefied, and some of them solidified, by 

 abstracting their heat and applying pressure. 



Air has been reduced to solid lumps by the reduc- 

 tion of the temperature alone. Oxygen has been 

 liquefied, but it has not yet been solidified. 



The lowest temperature yet obtained is minus 225° 

 0. Olzewski obtained this extremely low tempera- 

 ture by evaporating solid nitrogen in a vacuum. 



The absolute zero, or the point at which no heat is 



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