U1D5: Identifying the precision and number of Significant Figures in a measurement.Do Now: 1. Complete Measurement Lab (15 min) (Make sure that I check 1st try BEFORE you move on to 2nd try!)2. Complete: WS “Tools for Measurement” Today:3. To be able to determine the precision of a measure.

(followed by practice)4. To be able to determine the significant figures in a

measure (practice)5. Checkpoint!

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So….Let's review what we did in the measurement lab

Review Sheet (folder)

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So far so good…Let’s try Practice Packet #2

1 b) Were the measurements for the paper clips the same on each ruler? Explain

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What the heck are significant figures?

• Good question……• Significant = important• Figures = numbers• Aren’t all numbers important?– Not always

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Significant Figures

• aka: Reliable Numbers in a Measurement!

• In expressing the results of a measurement, one estimated figure is considered significant or reliable.

• The numbers that you record when doing a measurement are ALL reliable!

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To determine precision, we need to know Place Value!

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What is precision?• 2 meanings in science:–How close measures are to each other

(repeatability of data) – The number of digits to which a value has

been reliably measured.

• So… you tell me the rules of precision

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Find the pattern. Circled numbers are the level of precision. What’s my rule?

• 237.4653 g 100.001 cm 2 000 000 KL

• 1700 mm 0.0043 j 0.1 L

• 6300 Kg 750 000 Kj

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Rules for Determining Precision:

1) Decimal present:

2.10 g 136.111 g 5.1234 g 212 g 10.g

2) No decimal present:

3500 km 3500 km 120 km

the precision is the place furthest to the right ->

the precision is the place value of rightmost non-zero or zero with a line (bar) over it

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Practice

1. 734 g precision: _______________2. 5073.0 cm precision: _______________3. 150 mm precision: _______________4. 0.04 ml precision: _______________

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Significant figures: digits recorded by the measuring devise

A significant figure is ANY digit that is NOT a place-holding zero.A) SF:PH

(>1)B) 0.PH:SF (<1)

C) SF.SF

1000 0.21 1.071000 0.210 91.2051000 0.0013 1000.32000 0.00130 128.00032000 0.001030

The place occupied by the rightmost sig fig.Precision: the place the measuring device is read to.

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Rules for Sig Figs

1. Numbers less than one-> begin with 1st non zero and go right

ex. 0.043 mg -> 0.043 mg # s.f = _______ 0.060 L -> 0.060 L # s.f = _______ 0.00053 mm -> 0.00053 mm # s.f = _______

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2. Numbers one or greater a) no decimal, no line over zero… -> begin w/ leftmost non-zero go to the right most non-zero

12050 mL -> 12050 mL # s.f = _______ 1643 mL -> 1643 m # s.f = _______ 104 mL -> 104 mL # s.f = _______

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2. Numbers one or greater b) decimal -> all sig figs !!

12050. mL -> 12050. mL # s.f = _______ 1600. mL -> 1600. m # s.f = _______ 1.04 mL -> 1.04 mL # s.f = _______

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2. Numbers one or greater c) line over zero… -> left non- zero go to the zero mark

12000 mL -> 12000 mL # s.f = _______ 12000 mL -> 12000 mL # s.f = _______12000 mL -> 12000 mL # s.f = _______12000 mL -> 12000 mL # s.f = _______

Line tells you point of precision! Zeroes after are place holders

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Cool• Take this time to practice Sig Fig WS #1 and have

me check it

• Practice #2 TONIGHT

• Read page 8-9 in notes packet (vocab on front)