I PHYSICAL PROPERTIES AND STATES OF MATTER 3 



All these general properties can be brought together in a de- 

 finition thus : " Matter occupies space, offers resistance, 

 possesses weight, and transfers motion to other things 

 when it strikes against them." 



Other Properties of Matter. Matter possesses other cha- 

 racters or properties which it will be useful for us to study. 

 Though these, too, are general properties, it is possible to form 

 a good elementary notion of matter without taking them into 

 account, and it must be remembered that these properties 

 cdrniot all be applied to every kind of matter. We shall con- 

 sider (1) Divisibility, (2) Porosity, (3) Compressibility, (4) 

 Elasticity, (5) Inertia. 



Divisibility. Imagine some material body before you on a 

 table. You know that with suitable means you can divide it 

 into parts by cutting, that each of the halves can be again 

 divided, and that the bisection can be continued as long' as the 

 knife is sufficiently fine and sharp to be able to cut the substance. 

 Evidently, if you could only get sharper and sharper knives, 

 and keener and keener eyes, this process of division could be 

 carried on for a very long time. This property is what is 

 understood by divisibility. 



Could this division go on for ever ? There are reasons for be- 

 lieving that it could not. You could not go on dividing matter 

 indefinitely ; by and by extremely minute and indivisible parts 

 would be reached, called atoms. It must be at once understood 

 that atoms have never been seen. We can only imagine what 

 would be the end of our process of division. Our strongest 

 microscopes bring us nowhere near the possibility of seeing an 

 atom. 



Porosity. We are all in the habit of associating this property 

 with certain familiar forms of matter. The sponge we use in 

 the bath has holes through it, or is, as we say, porous. A piece 

 of blotting paper is another common example of an obviously 

 porous material ; the substances used in filters must also 

 evidently be porous, or else the water would not percolate 

 through them. Porosity refers to the possession of these 

 interstices or pores. In some cases, though we cannot see these 

 pores with the naked eye, we easily perceive them with a 

 microscope. The pores have often been shown to exist, even 

 where it is difficult to imagine their existence, by forcing water 

 through them. Thus Francis Bacon, in 1640, forced water 

 through a very carefully closed sphere made of lead. 



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