50 ELEMENTS OF LABORATORY WORK 



the tubes ; then place the flasks within a large vessel containing water, 

 and observe the alterations of each level while the temperature of the 

 water in the large vessel is being continuously raised by a flame. Keep 

 a record of the heights at different temperatures, and trace curves 

 which exhibit the relative changes of level. Observe also very carefully 

 the changes of level taking place as the liquids are cooled by being 

 surrounded by ice instead of water. 



8. Heat the end of a glass rod until it is soft, and then push into it 

 a piece of platinum wire. (Lengths suitable for subsequent use in the 

 chemical laboratory should be used.) Observe that the platinum is 

 tightly fixed after cooling, and give the reason. 



9. Show from the relation existing between the volume of a cube 

 and its linear dimensions that the coefficient of voluminal expansion 

 is slightly more than three times the linear coefficient, provided the 

 expansion is equal in all directions. 



10. Observe the different lengths of time occupied in bringing about 

 thermal equilibrium in the case of different kinds of matter. Goat rods 

 of glass, iron, and copper with paraffin, pass them through a cork to 

 the same distance, and fix the cork in a flask of boiling water. 



11. Why is thin glass less likely than thick glass to crack from a rapid 

 change of temperature ? 



12. Knowing that most gases increase by about -00366 of their 

 volume for an increase of 1 C., what is the density of air at 15 C. if 

 it is -0012932 at C. ? 



13. Observe the melting-point of paraffin and beeswax by placing a 

 small quantity of each in separate small tubes, fastening them to the 

 bottom of a thermometer, and immersing them in a beaker of water 

 which is gradually raised in temperature by a small flame. The water 

 should be heated slowly and constantly stirred. 



14. Suggest a method of showing change of temperature by the 

 expansion of air. How would you compare the readings of your in- 

 strument with those of an ordinary thermometer ? 



15. Temperature might be ascertained by means of a vessel con- 

 structed so that a liquid inside it would have to leave the vessel if it 

 expanded. From the relation between the quantities remaining and 

 the original quantity the voluminal expansion may be calculated, and 

 hence the temperature may be determined, if the rate of expansion for 

 the liquid is known, and if the starting temperature is known. Describe 

 an instrument of this kind and the use to which it can be put. 



16. Give descriptions of possible calorimeters, and mention the 

 advantages and disadvantages of each. 



17. The observed alteration of volume in a liquid contained in a 

 vessel is not the real change, for the capacity of the vessel itself is 

 simultaneously undergoing change. How may the absolute expansion 



