# Significant Figures Chem 140. Why significant figures? Weight of penny: 3 g ± 1 g Not very accurate Weight of truck: 41 057 214 g Also ± 1 g Much more.

## Presentation on theme: "Significant Figures Chem 140. Why significant figures? Weight of penny: 3 g ± 1 g Not very accurate Weight of truck: 41 057 214 g Also ± 1 g Much more."— Presentation transcript:

Significant Figures Chem 140

Why significant figures? Weight of penny: 3 g ± 1 g Not very accurate Weight of truck: 41 057 214 g Also ± 1 g Much more accurate Cardinal Scale Mfg. Co.

Why significant figures? Measure of accuracy 3 g Error: 33 % One significant figure

Why significant figures? Measure of accuracy 3 g Error: 33 % One significant figure 41 057 214 g Error: 0.0000024 % Eight significant figures

Rules for significant figures 1)Nonzero numbers: Always significant 2)Captive zeroes: Always significant 3)Leading zeroes: Never significant 4)Trailing zeroes: Significant when the decimal point is written

Examples 13060

Examples 13060 four s.f.

Examples 13060 four s.f. 13060.

Examples 13060 four s.f. 13060. five s.f.

Examples 13060 four s.f. 13060. five s.f. 0.001040

Examples 13060 four s.f. 13060. five s.f. 0.001040 four s.f.

Examples 13060 four s.f. 13060. five s.f. 0.001040 four s.f. 6.022 × 10 23

Examples 13060 four s.f. 13060. five s.f. 0.001040 four s.f. 6.022 × 10 23 four s.f.

Multiplying and dividing The number with the fewest s.f. determines how many are in the result.

Multiplying and dividing The number with the fewest s.f. determines how many are in the result. 0.043 × (6.022 × 10 23 ) = 2.58946 × 10 22

Multiplying and dividing The number with the fewest s.f. determines how many are in the result. 0.043 × (6.022 × 10 23 ) = 2.58946 × 10 22 = 2.6 × 10 22

Adding and subtracting Don’t count significant figures, count decimal places.

Adding and subtracting Don’t count significant figures, count decimal places. 3.54 + 0.0152 = 3.5552

Adding and subtracting Don’t count significant figures, count decimal places. 3.54 + 0.0152 = 3.5552

Adding and subtracting Don’t count significant figures, count decimal places. 3.54 + 0.0152 = 3.5552 3.56

Exact numbers Some numbers have infinite s.f. 60 seconds in a minute 2.54 cm in an inch 2 measurements being averaged

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