LAB Notes Significant Figures Narrated

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Significant Figures & Measuring Devices:

A graduated cylinder: 41.0 41.2 mL (more precise) 50 A beaker: 40. mL (not very precise) Significant Figures & Measuring Devices

Significant Figures & Measuring Devices:

Significant figures (“sig figs”): the digits in a measurement that are read from the measuring device, plus one estimated digit the digits in a measurement that are reliable, believable, trustworthy also called significant digits (“sig digs”) Significant Figures & Measuring Devices

Significant Figures & Measuring Devices:

Significant figures tell you how many believable, trustworthy digits there are in a given measurement. Significant figures tell you how detailed or precise the original measuring device was. Significant Figures & Measuring Devices

Significant Figures & Measurements:

Rules for determining which digits are significant in a given measurement: Significant Figures & Measurements Leading zeroes are NEVER significant. ( Leading zeroes are zeroes that appear before any non-zero digit in the measurement .) Example with leading zeroes: 0.0123 L

Significant Figures & Measurements:

Rules for determining which digits are significant in a given measurement: Significant Figures & Measurements Trailing zeroes are significant only if a DECIMAL is PRESENT. ( Trailing zeroes are zeroes that appear after any non-zero digit ) Example with trailing zeroes that are not significant: 123,000 m Example with trailing zeroes that are significant 1230.00 m

Significant Figures & Measurements:

Rules for determining which digits are significant in a given measurement: Significant Figures & Measurements 3 . All other digits are significant.

Determining Significant Figures Examples:

500 mL 1 significant figure (trailing zeroes only count if a decimal is present) 0.05 mL 1 significant figure (leading zeroes never count) 0.0500 mL 3 significant figures (leading zeroes never count, trailing zeroes only count if a decimal is present) 505 mL 3 significant figures (all other digits count) Determining Significant Figures Examples

The “Atlantic and Pacific” Rule:

The “Atlantic and Pacific” Rule Pacific Ocean Atlantic Ocean Another way to count significant figures (Based on a map of the United States and the locations of the 2 major oceans)

The “Atlantic and Pacific” Rule:

The “Atlantic and Pacific” Rule Decimal point is A BSENT. 40600 ft 2 3 sig figs ATLANTIC Count all remaining digits. Start on the “ A tlantic” side. (“Absent” and “Atlantic” both start with “A”) Cover up zeroes until you come to the first non-zero digit. Use the Atlantic & Pacific Rule to count the sig figs:

The “Atlantic and Pacific” Rule:

The “Atlantic and Pacific” Rule Decimal point is P RESENT. 0.01586 mL 4 sig figs PACIFIC Count the sig figs in the following measurement: Start on the “Pacific” side. (“Present” and “Pacific” both start with “P”) Cover up zeroes until you come to the first non-zero digit. Count all remaining digits.

Examples:

0.00932 Decimal point present → “Pacific” → count digits from left, starting with first nonzero digit = 3 sig figs 4035 Decimal point absent → “Atlantic” → count digits from right, starting with first nonzero digit = 4 sig figs 27510 Decimal point absent → “Atlantic” → count digits from right, starting with first nonzero digit = 4 sig figs Examples

Significant Figures & Measurements:

Significant figures are ONLY for MEASUREMENTS, NOT for counted values (as in, 25 desks) NOT for conversion values ( 1,000 g = 1 kg) Significant Figures & Measurements

Rounding to a specified number of Sig Figs:

Rounding to a specified number of Sig Figs Look at digit following the specified number of sig figs. If it is 5 or greater, then round up. If not, truncate (cut off the rest of the numbers). Round to 3 sig figs: 6.7512 m 6.75 m 6.78 m Round to 3 sig figs: 6.7777 m

Rounding to a specific number of Sig Figs:

Rounding to a specific number of Sig Figs Round to 4 sig figs: 6.7499 m - - - - 6.750 Round to 2 sig figs: 6.9521 m - - 7.0

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