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Chemistry LibreTexts

1: Introduction - The Ambit of Chemistry

The science of chemistry is concerned with the composition, properties, and structure of matter and with the ways in which substances can change from one form to another. Since anything that has mass and occupies space can be classified as matter, this means that chemistry is involved with almost everything in the universe. But this definition is too broad to be useful. Chemistry isn't the only science that deals with the composition and transformations of matter. Some matter is composed of cells, which transform by meiosis and other processes that biologists study. Matter is also composed of subatomic particles called leptons, which transform by processes like annihilation studied by physicists. Chemists are unique because they understand or explain everything, from our bodies to our universe, in terms of the properties of just over 100 kinds of atoms found in all matter and the amazing variety of molecules and other atomic-scale structures that are created by forming and breaking bonds between atoms.

  • 1.0: Prelude to Chemistry
    The science of chemistry is concerned with the composition, properties, and structure of matter and with the ways in which substances can change from one form to another. Since anything that has mass and occupies space can be classified as matter, this means that chemistry is involved with almost everything in the universe. But this definition is too broad to be useful. Chemistry isn't the only science that deals with the composition and transformations of matter.
  • 1.1: What Chemists Do
    What are some of the things that chemists do? Like most scientists, they observe and measure components of the natural world. Based on these observations they try to place things into useful, appropriate categories and to formulate scientific laws which summarize the results of a great many observations. Like other scientists, chemists try to explain their observations and laws by means of theories or models. They constantly make use of atoms, molecules, and other very small particles.
  • 1.2: Handling Large and Small Numbers
    Results often involve very large numbers or very small fractions. Such numbers are inconvenient to write and hard to read correctly. One approach involves what is called scientific notation or exponential notation.
  • 1.3: The International System of Units (SI)
    The metric system has undergone continuous evolution and improvement since its original adoption by France. Beginning in 1899, a series of international conferences have been held for the purpose of redefining and regularizing the system of units. In 1960 the Eleventh Conference on Weights and Measures proposed major changes in the metric system and suggested a new name — the International System of Units — for the revised metric system.
  • 1.4: SI Prefixes
    The SI base units are not always of convenient size for a particular measurement. For example, the meter would be too big for reporting the thickness of this page, but rather small for the distance from Chicago to Detroit. To overcome this obstacle the SI includes a series of prefixes, each of which represents a power of 10. These allow us to reduce or enlarge the SI base units to convenient sizes.
  • 1.5: Measurements, Quantities, and Unity Factors
    Let us assume that you are faced with a specific problem. Then we can see how scientific thinking might help solve it. Suppose that you live near a large plant which manufactures cement. Smoke from the plant settles on your car and house, causing small pits in the paint. You would like to stop this air-pollution problem—but how?
  • 1.6: Errors in Measurement
    Scientific measurements are of no value (or at least, they're not really scientific) unless they are given with some statement of the errors they contain. If a poll reports that one candidate leads another by 5%, that may be politically useful for the winning candidate to point out. But all respectable polls are scientific, and report errors.
  • 1.7: Volume
    Volume is the amount of 3D space a substance or object occupies. The most commonly used derived units are those of volume. As we have already seen, calculation of the volume of an object requires that all 3 dimensions are multiplied together (length, width, and height). Thus the SI unit of volume is the cubic meter. This is rather large for use in the chemical laboratory, and so the cubic decimeter or cubic centimeter are more commonly used.
  • 1.8: Density
    The terms heavy and light are commonly used in two different ways. We refer to weight when we say that an adult is heavier than a child. However, something else is alluded to when we say that oak is heavier than balsa wood. A small shaving of oak would obviously weigh less than a roomful of balsa wood, but oak is heavier in the sense that a piece of given size weighs more than the same-size piece of balsa. What we are actually comparing is the mass per unit volume, that is, the density.
  • 1.9: Conversion Factors and Functions
    The "dimensional analysis" we develop for unit conversion problems must be used with care in the case of functions. When we are referring to the same object or sample of material, it is often useful to be able to convert one parameter into another. Conversion of one kind of quantity into another is usually done with what can be called a conversion factor, that is based on a mathematical equation that relates parameters.

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