20 



EXPERIMENT 9. BOILING POINTS 



(a) Put some water into a flask and heat it over a Bun- 

 sen flame as in Figure 2. Note and record the reading of 

 the thermometer as soon as the water begins to boil, hold- 

 ing the thermometer in such a way that its bulb is im- 

 mediately below the surface of the liquid. The point to 

 which the mercury rises in a boiling liquid is called the 

 boiling point of the substance. 



(b) Repeat, using salt water. 



(c) Put some alcohol in a large test tube, and immerse 

 the lower end of the tube in a large vessel of boiling water. 

 Hold a thermometer in the test tube in such a way that 

 the bulb is below the surface of the liquid, but does not 

 touch the test tube. (The temperature of the tube may 

 differ from that of the alcohol.) Note and record the read- 

 ing of the thermometer when the alcohol begins to boil. 



EXPERIMENT 10. MELTING POINTS 



(a) Dip the bulb of a thermometer into melted paraffin, 

 then quickly withdraw it and allow the adhered paraffin 

 to harden. Insert the thermometer in a test tube and 

 place this in a larger vessel containing water. Heat the 

 water in the larger vessel. Note the reading of the ther- 

 mometer when the first drop of paraffin falls from the bulb. 

 Great care must be taken to keep the thermometer from 

 touching the side of the tube. 



(b) Find the temperature of melting ice by inserting 

 the thermometer in a funnel of cracked ice (Fig. 3), not- 

 ing readings at three-minute intervals until all the ice has 

 melted. 



