176 NATURE-STUDY LESSONS. 



8. (a) Place a pitcher or tumbler of cold water in a 



warm room. 



(d) What do you notice on the outside of the ves- 

 sel? 



(c) Where has it come from ? 



9. In what form did the moisture exist in the air ? 



10. Compare the temperature of the glass with that 

 of the atmosphere and its vapor. 



1 1. What effect on the vapor of the atmosphere had 

 its contact with the cold vessel ? 



12. How is the condition of invisible vapor affected by 

 its contact with a body of much lower temperature ? 



This change in its condition is called condensation. 



13. Under what circumstances is vapor condensed? 



14. {a) Breathe against a cold slate. 



{b) Explain the effect produced on the surface of 

 the slate. 



15. («) Why is the breath visible on a cold morning? 

 (J?) Why is it not visible on a warm morning ? 



16. Explain why windows in cold weather are clouded 

 with moisture. 



17. On which side of the window-pane is the mois- 

 ture found? Why? 



18. {a) In the experiment on boiling, Lesson L, No. 13, 



place the flame of the lamp close under where 

 the vapor first becomes visible. 



(b) What effect is produced ? 



{c) What caused this effect ? 



(</) How far from the tube can you see the vapor? 



{e) What becomes of it after this point? 



