GCSE Biology (AQA)

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Order of Magnitude

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Cell Biology Cell Structure

Order of Magnitude

4:08 Understanding Sizes of Cells
Spec 4.1.1.1
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  • Differences in size are often described as differences in the order of magnitude.
  • This concept allows for comparison between very large and very small numbers.
  • Example given: comparing the diameter of the Earth to that of a marble.
  • Earth's diameter: 12,742 kilometers; Marble's diameter: approximately 0.000013 kilometers.
  • By dividing the Earth's diameter by the marble's diameter, it is found that the Earth is about 980 million times larger than a marble.
  • Simplifying the comparison, the Earth's diameter is rounded to 13,000 kilometers, resulting in an approximate factor of 1 billion times larger than a marble.
  • Order of magnitude defined: the number of powers of 10 contained in a number.
  • Differences in order of magnitude are calculated in factors of 10 (e.g., 10 times bigger, 100 times smaller).
  • Example of order of magnitude: 10 has one order (10^1), 100 has two orders (10^2), and 1000 has three orders (10^3).
  • Increasing or decreasing a number by one order of magnitude involves multiplying or dividing the number by 10.
  • Order of magnitude calculations can be made using standard form to compare sizes more easily.
  • Example comparing the width of a human hair (100 micrometers) to the width of HIV (100 nanometers).
  • Conversion to standard form: 100 micrometers is 10^-4 meters, and 100 nanometers is 10^-7 meters.
  • Calculating the difference in order of magnitude involves dividing the powers of 10, resulting in a difference of three orders of magnitude.
  • This indicates that a human hair is 1000 times bigger than an HIV particle, as 10 to the power of three equals 1000.

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