Multiplying and Dividing Sig Figs
Download
Report
Transcript Multiplying and Dividing Sig Figs
Unit 2: Basic Math for
Chemistry
Lesson 1: Significant
Figures
Do Now: Express 44,300 in scientific
notation.
Book Section: 3.1
Accuracy is how close a measurement is
to the “correct” value.
Precision is how close measurements are
to each other.
Accuracy vs. Precision
Accuracy vs. Precision
In science, measurements have
precision, based on the tools we use.
The precision of the numbers is
determined by the number of significant
figures there are.
Significant Figures
All non-zeroes are significant (1-9).
◦ 423
Zeroes in the beginning… NEVER!!
◦ 0.124
◦ 0.000000053
Zeroes in the middle… ALWAYS!!
◦ 1204
◦ 6.0043
◦ 0.00809
Zeroes at the end… SOMETIMES!! (if there’s a decimal
point)
◦ 12400
◦ 1.2400
◦ 30400.
Counting Significant Figures
28.6 g
3400. cm
910 m
0.04604 L
0.0067000 kg
How Many Sig Figs?
Your answer will be rounded to the
place value of the least precise of the
original numbers.
25.1 g + 2.03 g
◦ 25.1 is precise to the tenths place
◦ 2.03 is precise to the hundredths place
◦ Your answer needs to be rounded to the
tenths place.
Adding and Subtracting Sig Figs
2.099 g + 0.05681 g
5.44 m – 2.6103 m
Practice - Adding and Subtracting
Sig Figs
2.099 g + 0.05681 g = 2.156 g
5.44 m – 2.6103 m = 2.83 m
DON’T FORGET UNITS!!!!
Practice - Adding and Subtracting
Sig Figs
Your answer will be rounded to the same
number of sig figs as the lowest number of
sig figs by an original number.
3.05 g / 8.5 mL
◦ 3.05 g – 3 sig figs
◦ 8.3 mL – 2 sig figs – answer gets rounded
to 2 sig figs
0.36 g/mL
Remember...treat units like algebra
◦ Grams divided by milliliters = g/mL
Multiplying and Dividing Sig Figs
2.4 g/mL x 15.82 mL
16.25 g / 5.1442 mL
Multiplying and Dividing Sig Figs
2.4 g/mL x 15.82 mL = 38 g
16.25 g / 5.1442 mL = 3.159 g/mL
Multiplying and Dividing Sig Figs
This Week
◦ Thursday – The Metric System (3.2) – HW 2-1
Due
◦ Friday – Pd. 4 Only – Dimensional Analysis
(3.3) – HW 2-2 Due
◦ VIDEO: Drew Brees vs. Archer
HW 2-1 Due Thursday