COMPOSITION OF LIFELESS AND LIVING THINGS 9 



it, and pour in some clear lime water, cork the 



bottle, and shake. 

 a. Tell what was done and describe the change that takes 



place in the lime water. 

 6. What substance is evidently formed when carbon 



burns in oxygen? 



6. When carbon is burned in oxygen, the two unite to 



form a new substance entirely different from 

 either carbon or oxygen. This new substance is 

 called carbon dioxid, because it is composed of one 

 part of carbon and two of oxgyen. 



a. Describe the composition of carbon dioxid. 



b. State the method by which carbon dioxid was pro- 



duced in this experiment. 



7. (Optional.) By means of a glass tube blow the breath from the 



lungs into a test tube of lime water, 

 a. What change do you notice in the lime water ? 

 6. What do you therefore conclude to be contained in the breath 



from the lungs ? 



12. Hydrogen (symbol, H) and water (formula, H 2 O). 

 Laboratory Study No. 4. Demonstration. 



Preparation of hydrogen (see Caution below) : Into a flask put 

 some pieces of zinc. (See Fig. 2.) Insert a stopper with two holes. 

 Through one of the holes pass the lower end of a thistle tube until 

 it nearly touches the bottom of the test tube, and through the other 

 run a short piece of glass tubing. To the upper end of the latter 

 attach by means of a piece of rubber tubing a delivery tube that will 

 reach beneath the surface of a tray of water such as that used in 

 collecting oxygen and in the preparation of carbon dioxid. Pour 

 through the thistle tube enough diluted hydrochloric acid to cover 

 the lower end of the thistle tube. (If hydrogen does not come off 

 rapidly enough, put into the flask a bit of copper sulphate.) After 

 the hydrogen has been given off for several minutes, collect a bottle 

 over water in the same manner as in the oxygen experiment. Re- 

 move the bottle, holding it upside down, and place it on the desk 

 in this position. Allow the bottle to stand till fumes disappear. 



