ACID, ALKALINE, AND NEUTRAL SUBSTANCES. 17 



the first and third saucers. Compare the 

 amount of evaporation in the three dishes. 

 What do you learn? 

 E. From the preceding experiments: 



1. Define evaporation. 



2. State three conditions that are favorable 



for evaporation. 



3. Name three ways in which evaporation can 



be lessened. 



7. ACID, ALKALINE, AND NEUTRAL 

 SUBSTANCES. 



Materials: Diluted hydrochloric acid, dilute caustic-soda solution, 

 water; red and blue litmus paper; evaporating-dish, alcohol or gas 

 lamp, glass stirring-rod. 



A. Tests for acid, alkaline, and neutral substances. 



1. Place a drop of diluted hydrochloric acid 



on blue litmus paper. Result? 



2. Place a drop of the diluted acid on the 



tongue. What is the taste? 



3. Put a drop of dilute caustic soda solution 



(which is alkaline) on red litmus paper. 

 Result? 



4. What is the taste of the caustic soda solu- 



tion? How does it feel when rubbed 

 between the thumb and forefinger? 



5. Put a drop of water on red and then on blue 



litmus paper. Water is a neutral sub- 

 stance. How does a neutral substance 

 affect litmus paper? 



