TASTE—IT’S THE STRUCTURE THAT COUNTS

Why do certain substances taste sweet, sour, bitter, or salty? Of course, it has to do with the taste buds on our tongues. But how do these taste buds work? For example, why does sugar taste sweet to us? The answer to this question remains elusive, but it does seem clear that sweet taste depends on how certain molecules fit the “sweet receptors” in our taste buds.

PROTECTING THE OZONE

Chlorofluorocarbons (CFCs) are ideal compounds for refrigerators and air conditioners because they are nontoxic and noncorrosive. However, the chemical inertness of these substances, once thought to be their major virtue, turns out to be their fatal flaw. When these compounds leak into the atmosphere, as they inevitably do, they are so unreactive they persist there for decades. Eventually these CFCs reach altitudes where ultraviolet light causes them to decompose, producing chlorine atoms that promote the destruction of the ozone in the stratosphere (see discussion above). Because of this problem, the world’s industrialized nations have signed an agreement (called the Montreal Protocol) that banned CFCs in 1996 (with a 10-year grace period for developing nations). So we must find substitutes for the CFCs—and fast.

SCHOOL CHEMISTRY LABORATORY SAFETY GUIDE

Recognition of laboratory safety and health problems has crystallized since the passage of the Occupational Safety and Health Act of 1970. This Act requires that certain precautions be observed to protect the safety and health of employees on the job. The employee designation includes all teachers employed by private and public school systems in States that have occupational safety and health plans accepted by the Occupational Safety and Health Administration (OSHA) of the U.S. Department of Labor (DOL). OSHA rules and regulations are provided to protect the employees and the facilities.

GUM THAT FOAMS

Mad Dawg chewing gum is a practical joker’s dream come true. It is noticeably sour when someone first starts to chew it, but the big surprise comes about ten chews later when brightly colored foam oozes from the person’s mouth. Although the effect is dramatic, the cause is simple acid–base chemistry.

The foam consists of sugar and saliva churned into a bubbling mess by carbon dioxide released from the gum. The carbon dioxide is formed when sodium bicarbonate (NaHCO₃) present in the gum is mixed with citric acid and malic acid (also present in the gum) in the moist environment of the mouth. As NaHCO₃ dissolves in the water of the saliva, it separates into its ions:

NUCLEAR WASTE DISPOSAL

Our society does not have an impressive record for safe disposal of industrial wastes. We have polluted our water and air, and some land areas have become virtually uninhabitable because of the improper burial of chemical wastes. As a result, many people are wary about the radioactive wastes from nuclear reactors. The potential threats of cancer and genetic mutations make these materials especially frightening.

Because of its controversial nature, most of the nuclear waste generated over the past 50 years has been placed in temporary storage. However, in 1982 the U.S. Congress passed the Nuclear Waste Policy Act, which established a timetable for choosing and preparing sites for the deep underground disposal of radioactive materials.