A student wants to know why sandhill cranes fly south for the winter. The student uses a map of North America to
make a model of the paths sandhill cranes take as they
migrate. The student draws lines with arrows to show the
routes sandhill cranes are known to take.
Which two issues describe limitations of the student's model?
I A. It does not explain how migrating birds affect trees.
OB. It does not explain why the cranes fly south.
C. It does not show the paths of other migrating bird species.
D. It does not show when the cranes arrive at each location.

explanation: it gains negative electrons, therefore becoming negatively charged. as charge cannot be created, nor destroyed, only transferred, this leaves the wool positive. now that they have opposite charges, the two items attract.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.

answer; the numbers of valence electrons in the acetic acid molecule (ch3co2h) is 24;