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Introduction to Chemistry - Measurement & Problem Solving

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이 집합의 용어 (23)

  • What is the difference between measured and exact numbers?
    Measured numbers are inexact and have uncertainty (e.g., 5.25 m). Exact numbers are counted values with no uncertainty (e.g., 24 students).
  • Why should units always be included in measurements?
    Units specify the quantity measured and are essential for clarity and correctness, e.g., write 3.1 miles, not just 3.1.
  • What does uncertainty in measurement mean?
    Uncertainty means the last digit in a measurement is estimated; no measurement is perfectly exact.
  • What are the two main measurement systems used in science?
    The English system and the metric system, with metric being more common due to powers of 10.
  • Define accuracy and precision in measurements.
    Accuracy is closeness to the true value; precision is consistency among repeated measurements.
  • How does the number of hash marks on a ruler affect measurement precision?
    More hash marks mean less uncertainty and higher precision in length measurements.
  • What is the difference between mass and weight?
    Mass is the amount of matter (grams), weight is the force of gravity on an object; on Earth they are often used interchangeably.
  • How is volume measured in the lab?
    Volume is measured using equipment like graduated cylinders, pipets, and burets, typically in liters or milliliters.
  • What is the significance of the meniscus in volume measurement?
    Volume should be read at the bottom of the meniscus, not the top, for accuracy.
  • Explain scientific notation and its use.
    Scientific notation expresses very large or small numbers as a decimal between 1 and 9 multiplied by 10 raised to an exponent.
  • How do you convert 5983 to scientific notation?
    Move decimal to get 5.983 and multiply by \(10^3\), so 5.983 x 10^3.
  • What are significant figures?
    Digits in a measurement that are known with certainty plus one estimated digit, reflecting precision.
  • List the rules for counting significant figures.
    Non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are not; trailing zeros depend on decimal presence.
  • How do you round numbers based on significant figures?
    If the digit to drop is 5 or greater, round up; if 4 or less, leave the last significant digit unchanged.
  • How do you handle significant figures in addition and subtraction?
    Answer should have the same number of decimal places as the measurement with the fewest decimal places.
  • How do you handle significant figures in multiplication and division?
    Answer should have the same number of significant figures as the measurement with the fewest sig figs.
  • What is a unit conversion factor?
    A ratio of two equivalent quantities used to convert units, e.g., 1 foot = 12 inches.
  • What are exact equivalents in unit conversions?
    Units exactly equal to each other with infinite significant figures, e.g., 1 liter = 1000 milliliters.
  • What is unit analysis in problem solving?
    A method that tracks units through calculations to ensure correct final units and prevent errors.
  • How is density defined and calculated?
    Density is mass per unit volume, calculated as \(\frac{mass}{volume}\), units like g/mL or g/cm3.
  • What does it mean if an object floats or sinks in water based on density?
    If density is less than 1.00 g/mL, it floats; if greater, it sinks.
  • How do you calculate volume by displacement?
    Volume of an irregular solid equals the difference between final and initial liquid volumes when submerged.
  • What is the percent concept in chemistry?
    Percent expresses a part-to-whole ratio as parts per 100, calculated as (part/total) x 100.