Here are three examples of the application of chemistry for the benefit of worldwide humanity.
1. Food Preservatives Chemistry: Since the time of cavemen there has been a need to preserve food so that it can be safely stored and eaten later, preventing wastage. In modern times with worldwide commerce there is a need to preserve fresh foods and produce, and to permit safe transport of these goods to regions in which the food items are not naturally available. In modern times food preservation technology makes food safe and nutritious. It permits packaging and labeling for the consumer, telling her of the safety of the food, its nutritious value, and a safe expiration date. Because of this technology modern man is no longer subject to the health hazards posed by contaminated or decayed food products.
2. Pharmaceuticals: Chemistry, particularly synthetic organic chemistry, along with pharmacology and fields in biology allow the pharmaceutical industry to produce medicines that are safe and effective. Through use of modern pharmaceuticals, physicians are able to treat and cure diseases including infectious diseases that in earlier days were fatal. The pharmaceutical industry as well as food preservative technology can share much of the credit for man's increased life expectancy over time.
3. Environmental Chemistry: This is the study of chemical and biochemical phenomena that occur in nature. It is through environmental chemistry that we now have an appreciation of some of the causes of (and possibly preventions of) global warming. In modern times, the application of environmental chemistry has effected a vast reduction in environmental pollution. In the past two decades, one of the best examples of this reduction is a several-fold decrease in air pollution from automobiles.
Explanation of references:
The first reference is a tutorial on food preservation chemistry. It includes the historic development of preservation technology.
The second reference defines pharmaceutical (medicinal) chemistry.
The last reference is a tutorial on global warming, including detailed information about the chemistry involved.