Introduction to Chemistry

Marie Curie

Marie Curie (1867–1934) discovered the radioactive metal radium. She is the only scientist to have won the Nobel Prize in two different science subjects — Physics and Chemistry. She also developed a portable X-ray machine that saved many lives during World War I. Alfred Nobel invented dynamite. William Ramsay discovered inert gases like helium and argon.

Protect food from microorganisms and prevent decomposition

Food preservatives are chemical substances added to food to protect it from microorganisms (like bacteria and fungi) and prevent decomposition. They help reduce food wastage and extend the shelf life of food. Examples include sodium benzoate, citric acid, and common salt (used in pickles). They do not add nutrition, colour, or sweetness — those are done by other types of food additives.

Nylon

Nylon is a synthetic fibre developed through chemistry. It is strong, wrinkle-resistant, and dries quickly. Cotton, wool, and silk are all natural fibres obtained from plants or animals. Synthetic fibres like nylon, polyester, and spandex are manufactured through chemical processes and are used to make towels, bed sheets, bags, and clothing. The development of synthetic fibres is one of chemistry's great contributions to the textile industry.

An explosive for national defence

Trinitrotoluene, commonly known as TNT, is a powerful explosive chemical used in national defence and military applications. It is one of the most commonly used explosives. It is NOT a food preservative, fertiliser, or medicine. Explosives like TNT fall under the 'dark side of chemistry' as they can cause massive destruction if misused. This is an important example of how chemistry can be both helpful and harmful.