I PHYSICAL PROPERTIES AND STATES OF MATTER 7 



into the liquid condition, and may be obtained in a kind of 

 transition stage neither true solid nor true liquid. 



EXPT. 8. Warm a Florence flask by twirling it between the 

 finger and thumb above the flame of a laboratory burner. 

 When it is too warm to bear the finger upon the bottom, intro- 

 duce a crystal of iodine, and notice it is at once converted into 

 a beautiful violet vapour. 



EXPT. 9. Warm a lump of sealing-wax or bicycle cement 

 in an iron spoon, and notice the gradual conversion into a 

 liquid. 



There is no hard and fast line between the three conditions of 

 matter we have mentioned. The reader will find as his know- 

 ledge extends that intermediate states are known between those 

 we have mentioned, but for the present it will be best to confine 

 the attention to this simple division, reserving for future work 

 a study of these gradations. We shall now consider the dis- 

 tinctive properties of solids, liquids, and gases* 



DISTINCTIVE CHARACTERS OF SOLIDS. 



A solid body does not readily alter its size or shape. It 

 will keep its own volume and the same form unless sub- 

 jected to a considerable force. Another way of expressing 

 the facts contained in the definition is to say that solids possess 

 rigidity. Hard solids are more rigid than soft ones. Liquids, on 

 the other hand, possess no rigidity, but the opposite property of 

 flowing or fluidity. Liquid particles slide over one another so 

 easily that the surface of a liquid at rest is always horizontal* 

 Fine sand may be made to flow, but the particles, however, do 

 not move freely over one another, so the surface is left uneven, 

 which fact provides us with a clear means of distinguishing 

 between a solid and a liquid. 



Solids possess Elasticity. It has been already shown by 

 Expt. 4 that elasticity can be called into play in solids by 

 pressure, and we have now to prove that it is also called into 

 play by pulling, bending, or twisting. 



It would take us farther into the subject of Physics than 

 we can afford space to describe how the elasticity has been 

 measured in these cases, but that there is an alteration of form 

 when solids are treated in these ways can be easily shown. 



