40 LABORATORY LESSONS IN GENERAL SCIENCE 



5. When a rubber eraser is under any strain, what marked 

 tendency as to form becomes at once apparent upon removal 

 of the stress? To what is this recovery of form to be at- 

 tributed? The property of matter thus made manifest is 

 known as elasticity. Formulate a definition for it, being 

 careful to include mention of the force upon which this 

 recovery of form depends. 



Gases have no form of their own, but when released from 

 pressure they regain the volume (size) they had before they 

 were compressed. Now re-word the definition for elasticity 

 to make it include the more or less complete recovery of 

 both size and form in bodies when any stress upon them is 

 removed. 



6. Try to break a piece of copper or iron wire by pulling 

 upon it, by bending it, and by twisting it. What resists 

 the efforts made? Say the wire has tenacity. In what 

 class of bodies (or what state of matter) must tenacity be 

 lacking? Define tenacity as a specific (not general) prop- 

 erty of matter. 



