40 LABOEATOEY MANUAL 



Apparatus 



Beaker Thermometer 



Salt 



Directions : Half fill a beaker with water. Carefully 

 observe and record its temperature. Into the water 

 put several teaspoonfuls of salt. Quickly insert the 

 thermometer into the beaker. Do you note any 

 changes in the temperature? What change is taking 

 place in the salt? What is necessary to produce this 

 change ? For your answer refer to Exercise 15. Then 

 how do you explain the change in temperature which 

 occurs ? Why is salt mixed with the ice in an ice cream 

 freezer? When snow melts, what effect does this have 

 on the surrounding temperature? Does this tend to 

 increase or decrease the rate of melting? Of what 

 advantage is this? 



Exercise 17. Change from Liquid to Solid. 

 Object: To determine the effect on the temperature 

 of a substance when it changes from a liquid to a solid. 



Apparatus 



Hypo Graduate 



Flask Bunsen burner 



Thermometer Wire gauze 



Cotton Ring stand 



Directions: Into the flask place 10 c.c. of water. 

 To this add 50 g. of hypo. Slowly heat the flask 

 until all of the hypo is dissolved. Close the mouth 

 of the flask with some cotton and very carefully set 

 it aside to cool. Take every precaution not to disturb 



