Question

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Convert 3.00 µm² Graphene Area to m²

Original question: Suppose that, from measurements in a microscope, you determine that a certain layer of graphene covers an area of 3.00 µm². Convert this to square meters. Express the area in square meters to three significant figures.

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Answer

The area of the graphene layer is 3.00×1012 m23.00 \times 10^{-12} \text{ m}^2. This result is obtained by squaring the linear conversion factor between micrometers and meters.

Explanation

Known:

  • Initial Area (AA): 3.00 µm23.00 \text{ µm}^2
  • Micro prefix (μ\mu): 10610^{-6}

Find:

  • Area (AA) in square meters (m2\text{m}^2)

  1. Identify the linear conversion factor The prefix "micro" (μ\mu) represents one-millionth of a unit. Therefore, there are 10610^6 micrometers in 1 meter, or 1 micrometer is equal to 10610^{-6} meters. 1 µm=106 m1 \text{ µm} = 10^{-6} \text{ m} A basic relationship showing that one micrometer is 10610^{-6} meters.

  2. Derive the area conversion factor ⚠️ This step is required on exams: When converting units of area, you must square the entire linear conversion factor. Failing to square the exponent is the most frequent source of error in dimensional analysis. (1 µm)2=(106 m)2(1 \text{ µm})^2 = (10^{-6} \text{ m})^2 Squaring both sides of the linear relationship to find the area ratio. 1 µm2=1012 m21 \text{ µm}^2 = 10^{-12} \text{ m}^2 Developing the conversion factor where 10610^{-6} becomes 101210^{-12} through the power of a power rule.

  3. Perform the substitution and calculation Multiply the given value by the derived conversion factor to cancel the square micrometers. A=3.00 µm2×(106 m1 µm)2A = 3.00 \text{ µm}^2 \times \left( \frac{10^{-6} \text{ m}}{1 \text{ µm}} \right)^2 Setting up the dimensional analysis calculation. A=3.00×1012 m2A = 3.00 \times 10^{-12} \text{ m}^2 The numerical result after applying the squared conversion factor.

  4. Unit and significant figure check The original measurement 3.003.00 has three significant figures. Our conversion factor is exact, so the final answer must maintain three significant figures. The units µm2\text{µm}^2 cancel out, leaving m2\text{m}^2. Units: µm2m2µm2=m2\text{Units: } \text{µm}^2 \cdot \frac{\text{m}^2}{\text{µm}^2} = \text{m}^2 Dimensional analysis proof showing that only square meters remain.

Final Answer

The area expressed in square meters to three significant figures is: 3.00×1012 m2\boxed{3.00 \times 10^{-12} \text{ m}^2}

Common Mistakes

  • Forgetting to square the prefix: Students often multiply 3.003.00 by 10610^{-6} instead of 101210^{-12}. Remember: if the unit is squared, the conversion factor must be squared (106×10610^{-6} \times 10^{-6}).
  • Significant figure neglect: Ensure you keep the ".00" in 3.00×10123.00 \times 10^{-12} to indicate that the measurement has a precision of three significant figures. Writing simply 3×10123 \times 10^{-12} would be incorrect in a laboratory context.
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