SUBSTANCES 5 



Now, why do all bodies occupy space? We answer by 

 saying that bodies are portions of matter, and that matter 

 occupies space. Matter not only occupies space, but it has 

 weight. When we give the weight of an object we give 

 the weight of the matter in it. 



5. Substances. While it is important for us to get 

 the general idea of matter, yet we always observe and 

 study matter in separate portions, or bodies (cf. 1). 

 Each body may be made up of one kind of matter or of 

 several kinds. Thus, we might have chips of marble, 

 each consisting of one kind of matter (marble), or we 

 might have chips consisting of a mixture of marble and 

 clay. The kinds of matter are called substances. The 

 qualities, or characteristics, of a body depend upon the 

 qualities of the substance or substances of which it is 

 composed. The qualities of a substance are called its 

 properties. We learn the properties of any given sub- 

 stance by the use of our senses or by experiment. 



Some illustrations will make clear the meaning of properties and the 

 difference between bodies and substances. A lake is a body of water; 

 water is not a body but a kind of matter, that is, a substance. A pencil 

 is a body consisting of the substances wood and "black lead," or 

 graphite (cf. 117). We can readily tell the wood from the graphite 

 by the properties of each. Thus, the wood is soft when cut; it is brittle, 

 light in color, and it floats upon water; it burns when heated in the air. 

 Graphite, on the other hand, has different properties. It too is brittle, 

 but its color is black, it sinks in water, burns with great difficulty, and 

 leaves a black mark when rubbed on paper. All these properties dis- 

 tinguish graphite from wood. 



Sulphur, or "brimstone," is another common substance. It is dis- 

 tinguished from wood and from graphite by the following properties: 



