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Scientists indicate the precision of measurements by the number of digits they report.
These rules are from page 47 of your text book:
An easier way to remember and use the rules! 
A Rule to Help: Pacific
A Rule to Help: Atlantic
If a decimal is Present, start at the
Pacific (left) side of the number.
Count the first non-zero number and all
numbers after that
If the decimal is Absent, start at the Atlantic
(right) side of the number.
Count the first non-zero number, and each
number after that.
Try these examples! How many sigfigs are there?
1) 6,589
___4___
5) 28.6
__3____
2) 480
___2___
6) 3440.
__4____
3) 0.00053 ___2___
7) 910
__2____
4) 0.00410 ___3___
8) 0.04200 __4____
Scientists often deal with very small and very large numbers, which can lead to a lot of confusion when
counting zeros! Can you image writing out the number for the mole in standard notation each time?
1 mol = 6.02 x 1023 = 602,000,000,000,000,000,000,000
What a mess! So we have learned to express these numbers as powers of 10. To convert a number to
scientific notation, you follow a few rules:
 Move the decimal until one non-zero digit appears to the left of the decimal.
 Be sure the power of the ten reflects the direction of that move.
 Keep the same number of significant figures in the scientific notation as your original.
 Numbers written in scientific notation ALWAYS contain all sigfigs
According to your textbook, “In scientific notation, numbers are written in the form M x 10n, where the
factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.”
Convert the following to scientific notation.
1. 0.005 hg = 5 x 10-3 hg
6. 0.25 L =
2. 5050 mL = 5.05 x 103 mL
7. 0.0250 kg = 2.50 x 10-2 kg
3. 0.0008 s =
8 x 10-4 s
8. 0.0025 J =
2.5 x 10-1 L
2.5 x 10-3 J
4. 1000 cm3 = 1 x 103 cm3
9. 500 nm = 5 x 102 nm
5. 1000000 mm = 1 x 106 mm
10. 5000. g = 5.000 x 103 g
Convert the following to standard notation.
1. 1.5 x 103 m =
1500 m
6. 3.35 x 10-1 mol = 0.335 mol
2. 1.50 x 10-3 kg =
0.00150 kg
7. 1.200 x 10-4 g =
0.0001200 g
3. 3.75 x 10-2 Hz =
0.0375 Hz
8. 1 x 104 cm3 =
10,000 cm3
4. 3.75 x 102 m2 =
375 m2
9. 1 x 10-2 s =
0.01 s
5. 2.2 x 105 mL =
220,000 mL
10. 4 x 100 dm =
4 dm
When taking measurements in science, always take the measurement one decimal place
beyond the tic marks!
73.0 mL
66.1 mL
This is not a great
measuring tool
because the
graduations go by
2’s!
2.65 cm
6.7 mL
3.40 cm
Because you are always making a “guessed” value in your measurements, there is
always some degree of uncertainty.
The last significant figure is the guessed value of the measurement!
This can tell you how good the measuring instrument is!
How would you report your measurements using these graduated cylinders?
56.0 mL
4.33 mL
23.6 mL
16.8 mL
76.0 mL
5.3 mL
32 mL
3.5 mL
47.0 mL