25) Plastics such as polyethylene and polypropylene are ubiquitous in our culture. As shown, the simple small molecules combine to form long polymer

chains. These polymer chains are held together by

to make

flexible, easily formable, and durable materials.

A) ionic bonds

B) covalent bonds

C) intermolecular forces

D) attraction and repulsion

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

elements make up everything, and they combine to make compounds.

the answer is c

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.