ELEMENTARY GENERAL SCIENCE 



CHAPTER I 



PHYSICAL PROPERTIES AND STATES OF MATTER 



What is meant by " Matter." Our earliest knowledge of 

 the world teaches us that on every side we have what we 

 familiarly speak of as things of all kinds. We become aware of 

 the existence of these things in different ways. Some we feel, 

 some we smell, some we see, some we taste, while others again 

 make their existence known to us by the sounds we hear. On 

 a windy day at the sea-side, standing on the beach, we feel the 

 ground under our feet ; we smell, it may be, the tar on a neigh- 

 bouring boat or the seaweed on the shingle ; we see a distant 

 ship at sea or the clouds hurrying across the sky ; we taste the 

 salt in the air ; and we hear the never-ceasing roar of the waves 

 as they break in at our feet. All these things, about which we 

 get to know by our senses, are called material things ; they are 

 forms of matter. We must think of matter, then, as meaning 

 all things which exist in or out of our world, which we can 

 become aware of by the help of our senses. 



Different kinds of Matter. Of course the number of 

 different kinds of things is innumerable, but yet they can all 

 be arranged in three classes, according to certain of the pro- 

 perties they possess and which we shall immediately have to 

 study. The classes are (1) Solid things or solids ; (2) Liquid 

 things or liquids ; (3) Gaseous things or gases. Sometimes the 

 last two are made into one class and called fluids. 



What is meant by " Properties." We shall have occasion 

 to use the word properties so often that it will be well to clearly 



B 



