18 MATTER AND ENERGY 



its motion ; again some force must be applied in some 

 way. 



This is one of the few properties that are common to 

 all matter. It will be treated more fully in 56, 59. 



QUESTIONS 



1. What is meant by the properties of matter? Name as 

 many as you can. Are any properties common to all forms of 

 matter ? 



2. What is meant by impenetrability? Name an example of 

 its effect. 



3. Define cohesion. Do the molecules of liquids cohere? Do 

 those of gases ? Explain how a blacksmith uses cohesion in 

 welding iron. 



4. Define adhesion. Name some substances that adhere to 

 each other. Which have the greater adhesion generally, solids 

 or liquids ? 



5. Upon what does hardness depend? How may iron be 

 hardened? How may a body be annealed? 



6. Name some substances that are brittle. How would you 

 test the brittleness of a body ? Are brittle substances ever 

 hard? 



7. What is meant by malleability? Would you expect a 

 brittle substance to be also malleable? Name some bodies of 

 matter that you think are malleable. 



8. Name some substances that you know to be ductile. How 

 do you know that they have this property? Is a malleable body 

 necessarily ductile ? 



9. How would you test the tenacity of a body ? 



10. What is commonly meant by a porous body ? What sorts 

 of bodies are porous ? 



11. What class of substances is most compressible? Explain 

 why bodies of matter may be thus compressed. 



12. Define elasticity. Is air elastic ? Is water elastic ? Name 

 some common uses of elasticity. 



