446 GENERAL SCIENCE 



Malleability. A property of matter which permits substances 

 to be pounded into thin sheets. For example, gold is very malle- 

 able. It may be pounded into a sheet as thin as 3 6 0*0 o o of an 

 inch thick. 



Tenacity. A property of matter which prevents bodies from 

 being easily pulled apart. 



Elasticity. A property of matter which causes it to resume its 

 original shape after some force has given it another shape. Steel, 

 rubber, glass, ivory, etc., are very elastic. 



Hardness and Softness. Properties of matter which are well 

 known to us. The diamond is the hardest known substance. 



Brittleness. A property of matter which allows matter to be 

 easily broken. Glass, china, etc., are good examples. 



Solutions. Place a crystal of potassium permanganate in a 

 flask of water. The permanganate will slowly dissolve and color 

 the liquid red. 



The dissolving of the permanganate illustrates the attraction of 

 the molecules of water for the molecules of potassium permanganate. 

 Sugar for sweetening coffee and salt for seasoning food are other 

 illustrations of this molecular attraction. Water dissolves many 

 substances, but there are substances which are not dissolved by 

 water. Water is called a solvent. Different liquids have different 

 solvent powers. Grease is not dissolved by water but by benzine, 

 beeswax by turpentine, resin and shellac by alcohol. For cleaning, 

 for preparing paint, and many other things, it is necessary to know 

 the proper solvent for different substances. 



Absorption of Gases. The molecules of many substances attract 

 the molecules of gases. Butter will have its flavor affected if any 

 substance is placed near it which is sending off a gas or odor. Water 

 absorbs air. Carbon dioxide is forced into water to produce soda 

 water. Heating substances which have gases dissolved in them 

 very often drives the gases off. Little bubbles of air may be seen 

 collecting on the inside of a glass of water which is standing in 

 a room. 



Crystallization. Any substances which have been dissolved in a 

 liquid will return to a solid state if the liquid is evaporated. Evapo- 

 ration of the liquid is an example of the molecules of a liquid escaping 



