Final answer:
When adding or subtracting numbers in scientific notation, convert them to the same exponent, and pay careful attention to significant figures and measurement uncertainty to accurately represent precision. Calculators may display extraneous significant figures that should be adjusted manually.
Step-by-step explanation:
When performing addition or subtraction with numbers expressed in scientific notation, it is important to consider significant figures (SFs) and measurement uncertainty. The numbers must first be expressed with the same exponent value. To illustrate, let's consider the sum of (1.36 × 10²) and (4.73 × 10³). The numbers must be converted so that they have the same exponent before the operation can be carried out.
Regarding uncertainty, when we add or subtract numbers, the uncertainty is determined by the least precise measurement. For example, when adding 16.7 g to 5.24 g, the result should be given to the tenths place, since 16.7 g is only precise to that place. Calculators may show more or fewer significant figures than legitimate based on this precision, requiring manual adjustment for accurate representation of certainty.
Caution is needed: Calculators often display additional significant figures that may not be present in the actual measurements. These extra figures need to be disregarded to ensure the final answer represents the true certainty of the values used.