6 ELEMENTARY GENERAL SCIENCE CHAP. 



collision with the slab, and, by virtue of its elasticity, it regained 

 its original size, causing the rebound. 



Inertia. This property will be considered more fully in a 

 later chapter, and we will let it suffice to say here that it is 

 entirely a negative property ; it may be expressed in a general 

 way by the statement that inanimate bodies are incapable by 

 themselves of changing their state of rest or motion. 



States of Matter. Solids, Liquids, Gases. The fact that 

 there are three kinds of material things is well known to every one, 

 and has been stated already. We must now add to this another 

 idea, viz. , that the same matter can exist in three different 

 states. 



EXPT. 5. Procure a lump of ice and notice that it has a 

 particular shape of its own, which as long as the day is 

 sufficiently cold, remains fixed. 



EXPT. 6. With a sharp brad-awl or the point of a knife 

 break it up into pieces, and put a convenient quantity of them 

 into a beaker. Place the beaker in a warm room, or apply 

 heat from a laboratory burner or spirit lamp. The ice dis- 

 appears, and its place is taken by what we call water. Notice 

 the characters of the water. It has no definite shape, for by 

 tilting the beaker the water can be made to flow about. 



EXPT. 7. Replace the beaker over the burner and go on 

 warming it. Soon, the water boils, and is converted into 

 vapour, which spreads itself throughout the air in the room, 

 and seems to disappear. The vapour can only be made visible 

 by blowing cold air at it, when it becomes white and visible, 

 but is really no longer vapour, but has condensed into small 

 drops of water. 



Here the same form of matter has been made to assume three 

 states ; in other words, ice, water, and steam are the same form 

 of matter in the solid, liquid, and gaseous state respectively. 



The change from one state to another may be sudden or 

 gradual. The circumstances attending the change from the 

 solid to the liquid, or from the liquid to the gaseous state, are 

 not always the same as we have seen in the case of water. 

 When solid iodine is heated, it appears to suddenly pass from 

 the condition of a solid to that of a gas. Camphor is another 

 instance of this sudden transition from solid to vapour. When, 

 on the other hand, sealing-wax is heated, it very gradually passes 



