Suggestions for Laboratory Work to Precede Chapter Eight 



1. Generate some carbon dioxid by pouring hydrochloric acid 

 on marble in a flask with a long delivery tube. Pass some of the 

 gas through clear limewater in a small beaker. What is the 

 effect? 



2. Blow your breath through a tube into another small beaker 

 containing limewater. Is the effect the same ? 



3. Arrange each of two small flasks with a two-hole stopper 

 and two tubes as shown in Figure 50. In the first flask put 

 flowers ; in the second put clear limewater. After they have 

 stood for a few minutes, draw air from the first flask through the 

 limewater in the second. Note the effect. Does the respiration 

 of plants produce the same gas as the respiration of animals ? 



4. Mark young leaves of fern, corn seedlings, and nasturtium 

 as suggested in the text, and study the growth of the three kinds 

 of leaves. 



5. Show by experiment that oxygen is necessary for the growth 

 of seeds. 



81 



