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gill of water in a plate, a cup, a bottle. Record the length 

 of time taken for the water to evaporate from each vessel. 

 Relate time to amount of heat and surface exposed. 



Hold a cold glass in steam. What causes the water to 

 form into drops. Blow your breath on a cold window pane. 

 Breathe deeply in cold air. What causes fogs, clouds, dew, 

 and frost? Relate evaporation and condensation to rain- 

 fall. 



(3) Put a thermometer into cold water. The mercury descends 

 in the tube. Heat the water. The mercury ascends in the 

 tube. Why? Heat expands liquids. 



3. Solids. 



(1) Fit a marble into a steel or iron ring. Heat the ring. The 



marble falls through. Why? Heat causes solids to ex- 

 pand. Cool the ring; the marble cannot fall through. Why? 

 Cold causes solids to contract. 



(2) Take a bar of iron which exactly fits into a hole. Heat the 



bar; it will no longer pass through. \Vhy? 



4. Questions. 



(1) W^hy does boiling water raise the tea-kettle lid? 



(2) Why does a hot lamp chimney break when a drop of cold 



water falls upon it? 



(3) Why is the tire of a wheel fitted while it is hot? Why is cold 



water then poured upon it? 



(4) In laying rails for a railroad why are the ends not fastened 



together. 



(5) Why do chestnuts burst open with a loud report when they are 



roasted? 



(6) Why does a punching ball become soft in the cold air when it 



was firm in a warm room? 



(7) Would the tires of a bicycle be firmer on a cold day or a warm 



day? 



