WHAT USES DO WE MAKE OF WATER? 99 



nitrogen ; (14) two electrons and one proton ; (15) one part oxygen 

 and two parts hydrogen. 



IV. In the process of making distilled water : (16) two changes 

 of state are required; (17) a source of heat is required; (18) a 

 source of cold is required to remove heat; (19) pure water must 

 be used to start with ; (20) sea water cannot be used. 



V. A water is safe to drink if it has been: (21) formed by 

 melting glacier ice ; (22) freshly distilled ; (23) filtered through 

 five layers of cloth ; (24) taken from a river ; (25) boiled 20 minutes. 



VI. Living things in water : (26) may be more numerous than 

 in an equal sized volume of land ; (27) are all microscopic in size ; 

 (28) are all animals, no plants being found there ; (29) often only 

 pass part of their lives there ; (30) all have to come to the surface 

 to breathe as there is no oxygen in the water. 



THOUGHT QUESTIONS 



1. Why will water clean some dirt spots better than others? 



2. What is a solvent? Find the names of three solvents and 

 name one important use of each. 



3. Does milk hold cream in solution? What makes cream rise ? 



4. If hydrogen will burn in the presence of oxygen, why doesn't 

 the hydrogen burn in water when water is composed of one atom 

 of oxygen and two atoms of hydrogen? 



REPORTS UPON OUTSIDE THINGS I HAVE 

 READ, DONE, OR SEEN 



1. Report upon an article related to some topic discussed in 

 this unit. The article may be from a current number of a science 

 magazine or from some popular science book you have read. 



2. The waters of the earth. 



3. Trips made by man down into the ocean. 



4. Uses boys and girls make of water. 



5. Water : in and out of the air. 



SCIENCE RECREATION 



1. MAKE HYDROGEN BALLOONS 



Prepare hydrogen gas from dilute hydrochloric acid by action 

 on zinc scraps. Carry the gas through water to wash it. The 

 hydrogen is discharged from the end of a fire polished glass tube 



