8.11C Human Dependence on Ocean Systems Artificial reefs, such as old ships placed in the ocean by humans, affect the ecosystems of
the ocean. How can these artificial reefs change the ecosystem?
A. Artificial reefs provide less protection to small fish.
B. Artificial reefs provide a new habitat for organisms.
C. Artificial reefs provide more oxygen to organisms.
D. Artificial reefs provide additional locations to drill for
oil.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.

gasoline is a mixture. it contains several different kinds of compounds that can be present in a variety of ratios.