Name:______________________________
Date:_____________________ Pd:___________
Title: Measurements in Chemistry
Essential Question: Essential Question: What are some of the things you need to know about taking
measurements or expressing answers to calculations and how do we apply this knowledge?
Level Questions
Accuracy and Precision
Accuracy is how close a measured value is to the actual (true)
value.
Precision is how close the measured values are to each other.
Significant Figures:
a.
50.3 m has =___ sig. figs.
b.
3.0025 s has = ___ sig figs
c.
0.892 kg has = ___ sig figs
d.
0.0008 ms has = _____sf
e.
57.00 g has =_______sf
f.
2. 000 000 kg has =____sf
g.
1000. L ( measured )=______sf
The number of significant figures in a measurement, such as 2.531, is
equal to the number of digits that are known with some degree of
confidence (2, 5, and 3) plus the last digit (1), which is an estimate or
approximation. As we improve the sensitivity of the equipment used to
make a measurement, the number of significant figures increases.
Significant Figure Rules
1.
2.
3.
4.
5.
All nonzero digits are considered significant.
Zeros between other nonzero digits ARE significant.
Zeros IN FRONT of nonzero digits are NOT
significant
Zeros that are at the END of a number AND to the
right of the decimal ARE significant.
Zeros at the end of the number but to the LEFT of the
decimal are significant IF they have been MEASURED
or are the first ESTIMATED digit; otherwise, they are
not significant.
Significant figures: Addition and Subtraction
For addition and subtraction, look at the decimal portion (i.e., to the right of
the decimal point) of the numbers ONLY. Here is what to do:
1) Count the number of significant figures in the decimal portion of each
number in the problem. (The digits to the left of the decimal place are not
used to determine the number of decimal places in the final answer.)
2) Add or subtract in the normal fashion.
3) Round the answer to the LEAST number of places in the decimal portion
of any number in the problem.

Example: 5.146 + 5.29 = 10.44
You Try:
a) 16.5 + 9 + 5.251 = _________
b) 12.944 – 2.8 = _____________
Significant Figures: Multiplication and Division
The following rule applies for multiplication and division:
The LEAST number of significant figures in any number of the problem determines the
number of significant figures in the answer
Example: 2.200001  2 = 4
You Try:
a) 8.362 x 1.00 = __________
b) 2 x 56 = ____
c) 0.00043 x 4.2434 = ______
Name:______________________________
Date:_____________________ Pd:___________
Title: Measurements in Chemistry
Essential Question: Essential Question: What are some of the things you need to know about taking
measurements or expressing answers to calculations and how do we apply this knowledge?
Scientific Notation
Level Questions
A way of writing numbers that are too big or too small to be
conveniently written in decimal form.
Big Numbers have positive exponents
602,000,000,000,000,000,000,000
This would be written as:
23
6.02 x 10
Small Numbers have negative exponents
0. 000 000 000 000 000 000 000 327
This would be written as:
-22
3.27 x 10
How to write numbers in Scientific Notation
To change any number to scientific notation, move the decimal point
directly behind the very first digit, counting how many places you move.
Look at these examples:
These examples are all BIG numbers (or numbers greater than one) so
the exponents are positive and the decimal point is moved to the left.
4
36,000 meters =3.6 x 10 m
I moved the “understood” decimal 4 places to the left   
8
245,000,000 buttons = 2.45 x 10 buttons:
I moved the understood decimal 8 places to the left.
2
150. grams = 1.50 x 10 grams:
I moved the decimal 2 places to the left.
These examples are all Small numbers (or less than 1) so the exponents
are negative and the decimal point is moved to the right.
0.000 000 43grams = 4.3 x 10 -7g
I moved the decimal 7 spaces to the right.
You Try
-1
0.80 ml = 8.0 x 10 ml
I moved the decimal 1 space to the right.
8
1) 2.36 x 10
-3
2) 7.8 x 10
-6
3) 3.92 x 10
5
4) 5.43 x 10
Summary:
Name:______________________________
Date:_____________________ Pd:___________
Title: Measurements in Chemistry
Essential Question: Essential Question: What are some of the things you need to know about taking
measurements or expressing answers to calculations and how do we apply this knowledge?