1. Chemistry is the study of matter and how it reacts.
What is Chemistry?
matter
The “stuff” in the universe is made
of “building blocks” formed in stars.
atoms/elements
Chemistry is the study of matter and how it reacts.
To study matter and its reactions, we’re going to need to make a lot of measurements…
To study matter, we’ll need to make a lot of measurements…

2. unit Measurement number 42.5 g 1.05 mL 16 cm measurement:
quantity with _______ and a _____.
42.5 g mL 16 cm
number
unit

3. Scientific Notation = 1 x 1014 atoms = 1 x 10–11 meters
a really big number: 100,000,000,000,000
(atoms in a cell)
or really small number: meter
(size of one atom)
numbers without placeholder zeroes
by using powers of 10.
= 1 x 1014 atoms
Expressing very large numbers, such as the estimated number of stars in a galaxy, is easier if scientific notation is used. Do some on the board as examples of moving decimal back and forth (10 min)
= 1 x 10–11 meters

4. Accurate and Precise but not Neither Precise Nor Accurate _______
Yes good acc poor prec is possible with average
Accurate
and
Precise
but not
Neither Precise
Nor
Accurate
_______
Precise
________
Accurate

5. Accuracy, Precision, and % Error
Accurate:
close to the accepted or true value
Precise: (repeatable)
close to each other
(last digit varies little)
Acc
Neither
Prec

6. Accuracy, Precision, and % Error
(difference)
% Error = (________) x 100%
acc
exp – acc
exp – experimental value
acc – accepted value
(Is being off by 9 cm a lot or a little? It depends on whether you
are measuring the length of a piece of paper or the distance to here to Philly for the X Games.

7. % Error Calculation: % Error = |exp – acc| x 100% acc
What is the % error if a measurement of 96.8oC is made, but the accepted (true) temperature is 99.1oC?
% Error = |exp – acc| x 100%
acc
% Error = |96.8 – 99.1| x 100%
99.1
% Error =
2.32%

8. Quick Quiz!
1. What is one reason to study chemistry?
to pass the test
you need it before driver’s ed
to be the coolest kid in school
to explain the natural world around you

9. Quick Quiz.
2. Which of the following expressions has NOT been correctly changed to sci. not.?
=  10–3
=  10–5
8,426,000 =  106
45, =  103
(Do these on board)

10. Quick Quiz.
3. Which set of measurements of a 2.00 g object is the most precise?
2.0 g , 2.1 g , 2.0 g
2.10 g, 2.00 g, 2.20 g
2.05 g, 2.04 g, 2.03 g
1.50 g, 2.00 g, 2.50 g