12 PRELIMINARY EXPERIMENTS 



off smoke ? If so, its color and amount. Describe the ash, 

 its color, and amount. 



Put a small quantity of limewater in a test tube and shake 

 it. Does any change occur? Now ignite the charcoal 

 stick, and while it is glowing red-hot plunge it into the tube 

 of limewater, but not down into the limewater. Withdraw 

 the charcoal, and holding the thumb over the mouth of the 

 tube, shake it. What change takes place? This is the test 

 for carbon dioxide. 



Through a straw or piece of glass tube, breathe into a tube 

 of fresh limewater, letting the breath bubble through the 

 liquid. What is the result? 



Conclusion. State properties of carbon. What forms 

 when it burns ? How is the presence of carbon dioxide 

 detected ? What proof that it is contained in our breath ? 



Note. Limewater is made by placing a considerable quantity 

 of water on slacked lime, shaking it well, and allowing it to settle. 

 The clear liquid on top is limewater. 



Definition. Combining two or more elements to form 

 a compound is called synthesis. 



In burning charcoal, the element carbon united with the 

 element oxygen in the air to make the compound carbon 

 dioxide. 



Changes like these are known as chemical changes because 

 the original substances lose their properties and new sub- 

 stances are formed having new properties. 



Thus the blackness, brittleness, etc., of the carbon disap- 

 peared and the different properties of carbon dioxide ap- 

 peared. 



Query. In what respects does the experiment with lime- 

 water demonstrate a chemical change ? 



