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General Chemistry: Measurement, Properties, and Separation Techniques

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Termini in questo insieme (24)

  • Accuracy

    Accuracy is how close a measured value is to the true or accepted value.

  • Precision

    Precision is how reproducible or consistent repeated measurements are, regardless of closeness to the true value.

  • Difference between accuracy and precision

    Accuracy measures closeness to true value; precision measures consistency of repeated measurements.

  • Recording measurements and uncertainty

    Record all certain digits plus one estimated digit; the last digit is uncertain and reflects measurement precision.

  • Significant figures (sig figs)

    Significant figures indicate the precision of a measured value based on counting rules related to zeros and decimal points.

  • Counting significant figures with decimal point

    Count digits from left to right starting at the first nonzero digit when a decimal point is present.

  • Counting significant figures without decimal point

    Count digits from right to left starting at the first nonzero digit when no decimal point is present.

  • Significant figures in exact counted values

    Exact counted values (e.g., 12 eggs) have an infinite number of significant figures.

  • Sig figs in 0.00450

    The number 0.00450 has three significant figures: 4, 5, and the trailing 0.

  • Sig figs rule for multiplication/division

    Result should have as many significant figures as the value with the fewest significant figures.

  • Sig figs rule for addition/subtraction

    Result should have as many decimal places as the value with the fewest decimal places.

  • Base SI units in chemistry

    Mass: kilogram (kg), Length: meter (m), Time: second (s), Temperature: kelvin (K), Amount: mole (mol), Electric current: ampere (A), Luminous intensity: candela (cd).

  • Dimensional analysis

    Method for converting units using conversion factors so unwanted units cancel, leaving the desired unit.

  • Five areas of chemistry

    Analytical, Biochemistry, Inorganic, Organic, and Physical Chemistry.

  • Pure science vs. applied science

    Pure science builds knowledge for its own sake; applied science uses knowledge to solve practical problems.

  • Intensive properties

    Properties that do not depend on the amount of substance, e.g., color, density, boiling point, temperature.

  • Extensive properties

    Properties that depend on the amount of substance, e.g., mass, volume, length, energy.

  • Homogeneous mixtures

    Mixtures with uniform composition throughout, e.g., air, saltwater.

  • Heterogeneous mixtures

    Mixtures with non-uniform composition, e.g., oil and water, salad.

  • Filtration

    Separation technique using a porous barrier to separate solids from liquids, e.g., sand from water.

  • Evaporation

    Removes liquid from a solution to recover dissolved solids, e.g., salt from saltwater.

  • Distillation

    Separates substances based on differences in boiling points, e.g., separating alcohol from water.

  • Extraction/Separatory funnel

    Separates components based on solubility in different immiscible liquids, e.g., separating oil from water.

  • Example of separating sand and salt

    Add water to dissolve salt, filter to remove sand, then evaporate water to recover salt.