HEL ASA SCUBA divers are at risk of developing a life-threatening condition called Decompression Sickness (a. k.a. “the Bends”) if they return to the surface too quickly. Decompression sickness is caused by bubbles of gas dissolved in the blood stream. These bubbles expand in the blood stream, increasing in volume, and block the flow of blood throughout the body. As divers descend farther underwater, the pressure from the weight of all the water above them increases tremendously which compresses the gases in their blood. How can a diver rising quickly back to the surface cause Decompression Sickness?

A.
As a diver rises, the pressure on their body decreases which allows the volume of the gas to increase.
B.
As a diver rises, the pressure on their body increases which allows the volume of the gas to decrease.
C.
As a diver rises, the pressure on their body decreases which allows the volume of the gas to decrease.
D.
As a diver rises, the pressure on their body increases which allows the volume of the gas to increase.

explanation:

the largest database of organic compounds lists about 10 million substances, which include compounds originating from living organisms and those synthesized by chemists. the number of potential organic compounds has been estimated at 1060—an astronomically high number. the existence of so many organic molecules is a consequence of the ability of carbon atoms to form up to four strong bonds to other carbon atoms, resulting in chains and rings of many different sizes, shapes, and complexities. the simplest organic compounds contain only the elements carbon and hydrogen, and are called hydrocarbons. even though they are composed of only two types of atoms, there is a wide variety of hydrocarbons because they may consist of varying lengths of chains, branched chains, and rings of carbon atoms, or combinations of these structures. in addition, hydrocarbons may differ in the types of carbon-carbon bonds present in their molecules. many hydrocarbons are found in plants, animals, and their fossils; other hydrocarbons have been prepared in the laboratory. we use hydrocarbons every day, mainly as fuels, such as natural gas, acetylene, propane, butane, and the principal components of gasoline, diesel fuel, and heating oil. the familiar plastics polyethylene, polypropylene, and polystyrene are also hydrocarbons. we can distinguish several types of hydrocarbons by differences in the bonding between carbon atoms. this leads to differences in geometries and in the hybridization of the carbon orbitals.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.

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.