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Ch.1 - Matter, Measurement & Problem Solving
All textbooksTro 4th EditionCh.1 - Matter, Measurement & Problem SolvingProblem 112
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Chapter 1, Problem 112

Why does a temperature measurement of 25 °C have three significant figures, while a temperature measurement of -196 °C only has two significant figures? Explain.

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1
Understand the concept of significant figures: Significant figures are the digits in a measurement that are known with certainty plus one estimated digit.
Identify the significant figures in positive temperatures: For 25 °C, the digits '2' and '5' are known with certainty, and there is no decimal point, so both are significant, giving us two significant figures. The absence of a decimal point implies that the zero is not significant.
Identify the significant figures in negative temperatures: For -196 °C, the digits '1', '9', and '6' are known with certainty, and there is no decimal point, so all three are significant, giving us three significant figures.
Consider the role of the negative sign: The negative sign in -196 °C is not a digit and does not affect the count of significant figures.
Conclude the explanation: The difference in significant figures arises from the presence or absence of a decimal point and the certainty of the digits, not from the negative sign.
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