II. INTRODUCTORY EXPERIMENTS IN CHEMISTRY 



AND PHYSICS 



In the introductory chapter we learned that science concerns 

 itself with matter, and that the science of biology is concerned 

 with the study of this matter when it is in a living state. In 

 order to understand this definition we must first get a conception 

 of what matter really is. 



Matter. — If you take a piece of ice in your hand, you are aware 

 that it is cold, and that it has weight and a certain form. We 

 call it a solid. A few minutes' exposure to the warmth of your 

 hand will change this solid into a liquid. If the water thus 

 formed be heated over a flame until it boils, it may be changed 

 again, this time into a gas which passes off into the air and be- 

 comes invisible. The ice has successively changed from a solid 

 to a liquid and then to a gas. In each state we could measure 

 it and weigh it. In each form it occupies space. It must be 

 considered matter, whether in the form of a solid, a liquid, or a 

 gas. 



Physics and Chemistry. — The sciences which treat chiefly of the 

 properties and forces of inorganic or dead matter, and of the rela- 

 tions of the parts of the substances composing it, are known as 

 the sciences of physics and chemistry. 



Chemical Element. — All the building materials of this uni- 

 verse, both living and lifeless, are classified by chemists as either 

 chemical elements or chemical compounds. A chemical element is so 

 simple in its structure that it cannot be broken or decomposed 

 into a simpler substance. Examples of such substances are oxy- 

 gen, making up about one fifth of the atmosphere; nitrogen, com- 

 posing nearly all the remainder of pure air; carbon, an element 

 that enters into the composition of all organic living things or 

 those that once possessed life; and over sixty others of more 

 or less importance to us in the study of biology. 



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