STATES OF MATTER 91 



30. Molecules. — We have been speaking of particles. 

 We have spoken of particles of sugar which become equally 

 distributed throughout tea, and of the particles in the 

 water of the soil which plants use in making food. A 

 particle of a substance is, of course, any very small part of 

 it. You may have wondered how small these particles of 

 sugar are in a solution. We cannot tell you just how small 

 they are, but we can tell you that they are just as small 

 as sugar can be and yet remain sugar. They are molecules. 



Molecules are the smallest particles into which any sub- 

 stance can be divided and yet remain the same substance. 

 There are processes by which a molecule of sugar can be 

 reduced, but it then ceases to be a molecule of sugar. It 

 becomes molecules of other things. 



This is another place where you must call on your 

 imagination to help you out. We cannot actually show 

 molecules to you. It requires thousands of them to make 

 a particle large enough to be visible to the naked eye. 

 Yet we know that they exist. We know that all sub- 

 stances are composed of them. This has been proved. 



31. States of Matter. — All substances are examples of 

 what is called matter. Anything that can be weighed and 

 measured is matter. Matter occurs in three different con- 

 ditions or states. There is the solid state, the liquid 

 state, and the gaseous state. That is, matter may be a 

 soHd, a liquid, or a gas. And it may pass from one of 

 these states into another. In passing from one of these 

 states into another it may change the nature of its mole- 

 cules or it may not; that is, it may become a different 

 kind of substance or it may remain the same substance, 

 different only in state. 



