92 EXPERIMENTAL GENERAL SCIENCE 



23. Which makes a better holder for flat-irons and cooking utensils, 

 a cotton or a woolen cloth? Why? 



24. Why are the handles of tea kettles, coffee pots, and the like usually 

 made of wood instead of metal? 



25. In which could you heat water more quickly, a tin or a china 

 cup? 



26. Frozen mercury thrown into water soon melts, but the water 

 becomes solid. How do you explain this? 



27. A kettle of liquid air will boil if set on a cake of ice. Where does 

 it get the heat for this? 



28. In canning, why do people often put a silver spoon in the jar 

 before putting in the hot fruit? 



29. On which would a kettle of hot water cool more quickly, iron or 

 wood? Why? 



30. Should a coffee pot have a smooth or a rough surface? Why? 



31. In the air-cooled gas engine, the cylinders have many projections 

 on them. Why? 



32. Which should be warmer in the sunshine, a polished shoe or 

 dusty one? 



33. Why do people wear white in summer and black in winter? 



34. A black soil is regarded as a warm soil. Why? 



