Chemistry students at Kenya Science Teachers College in Nairobi, Kenya, study the molecular reactions of a substance. Chemists use the measuring unit of a mole to describe the molecular amount of a substance.
Photograph by Bruce Dale, National Geographic

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    On October 23, 1991, chemistry teachers first celebrated Mole Day—encouraging students to take a fun interest in chemistry as a class and a career. Mole Day is a key part of Chemistry Week, which raises awareness about the importance of chemistry in everyday life. Chemists make life easier for travelers (developing effective paint for road markings); health care officials (creating effective dental anesthetics or contact lens solutions); and consumers (developing everything from silly string to chewing gum).
    What does a mole have to do with chemistry? A mole, abbreviated mol, is a basic measurement in chemistry. According to the National Mole Day Foundation, “one mole is a mass (in grams) whose number is equal to the molar mass of the molecule. For example, the water molecule has a molar mass of 18, therefore one mole of water weighs 18 grams.”
    One mole of any substance usually contains Avogadro's Number of molecules or atoms of that substance. Avogadro’s Number is 6.02x1023. For this reason, Mole Day officially starts at 6:02 a.m. on October 23 (10-23) and ends at 6:02 a.m. the following morning. This goofy awareness is also reflected in the themes for Mole Day: The Mole the Merrier (1991); Celebrate the Molennium (2000); or Molar Eclipse (2012), for example. In 2014, the Mole Day theme (Mole-o-ween) complemented the theme of Chemistry Week—"The Sweet Side of Chemistry: Candy."
  • Term Part of Speech Definition Encyclopedic Entry
    anesthetic Noun

    substance that reduces the awareness of physical sensation.

    atom Noun

    the basic unit of an element, composed of three major parts: electrons, protons, and neutrons.

    career Noun

    long-term job or occupation.

    celebrate Verb

    to observe or mark an important event with public and private ceremonies or festivities.

    chemistry Noun

    study of the atoms and molecules that make up different substances.

    complement Verb

    to complete or make a positive addition to.

    consumer Noun

    person who uses a good or service.

    contact lens Noun

    small plastic disk that fits over the cornea (eyeball) to correct vision.

    dental Adjective

    having to do with teeth.

    health care Noun

    system for addressing the physical health of a population.

    mass Noun

    measure of the amount of matter in a physical object.

    measurement Noun

    process of determining length, width, mass (weight), volume, distance or some other quality or size.

    mole Noun

    basic unit in the International System of Units (SI), representing the amount of a substance (in grams) containing as many atoms, molecules, or ions as the number of atoms in 12 grams of carbon-12 (which is Avogadro's number, or 6.022 × 1023).

    molecule Noun

    smallest physical unit of a substance, consisting of two or more atoms linked together.

    particle Noun

    small piece of material.