Calibration, the Blank and What Makes a Measurement Trustworthy · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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From instrument signals to trusted numbers

Science · Chemistry · ages 18-19
Name ______________________   Date ____________

  1. What does the blank correct for?

    • Background signal present without the analyte
    • Shifts in how the analyte itself responds
    • Mistakes in weighing the sample

  2. Why must calibration standards bracket the sample?

    • So the line looks longer on the graph
    • So the sample is read between standards, not beyond them
    • So every standard gets used at least once

  3. You may delete an outlier just because it spoils a neat line.

    Circle one:   True   False

  4. For that seawater metal measurement, what should the blank be?

    • Pure analyte with no water at all
    • The same seawater matrix minus the analyte
    • An empty dry instrument reading

  5. A metal must be measured in seawater. Which calibration approach fits?

    • External calibration with pure water standards
    • Internal standard with a clean solvent
    • Standard addition into the seawater itself

  6. When should you choose an internal standard over external calibration?

    • When sample is lost unevenly during preparation
    • When the samples are perfectly clean waters
    • When only one standard exists

  7. Can the blank correct for a matrix effect? Explain your verdict.

    • No, it cannot fix how the matrix changes the response
    • Yes, blanks fix every kind of error
    • Yes, if you measure the blank twice

  8. A calibration line looks perfect, yet results run consistently high. What is the likely cause?

    • The blank was measured twice
    • The instrument needs recalibrating daily
    • A matrix effect biases every result
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Answer key

For grown-ups. Fold this page away before handing over the rest.

From instrument signals to trusted numbers W1-mt_UNkQFonlWJ-s1

  1. Background signal present without the analyte · Blanks subtract background, not broken responses.
  2. So the sample is read between standards, not beyond them · Reading between standards is interpolation you can trust.
  3. False · Deletions need proof of a concrete mistake, stated openly.
  4. The same seawater matrix minus the analyte · Blanks mimic everything except the thing measured.
  5. Standard addition into the seawater itself · Adding standards to the sample carries the matrix along.
  6. When sample is lost unevenly during preparation · The internal companion suffers the same losses and corrects them.
  7. No, it cannot fix how the matrix changes the response · Background subtraction and response shifts are different jobs.
  8. A matrix effect biases every result · Good looking lines can still sit on shifted responses.
Worksheet · LightMySky