Transcript Numbers in Science

Numbers in Science
Chemists deal with very large numbers…
602000000000000000000000
(Do you recognize this number?)
Examples of Scientific Notation
 Given: 289,800,000
 Use: 2.898 (moved 8 places)
 Answer: 2.898 x 108
 Given: 0.000567
 Use: 5.67 (moved 4 places)
 Answer: 5.67 x 10-4
Example
 Given: 5.093 x 106
 Answer: 5,093,000 (moved 6 places to the right)
 Given: 1.976 x 10-4
 Answer: 0.0001976 (moved 4 places to the left)
Practice problems
 12300=
1.23 x 104
 2.5x103=
2,500
 1.0x10-6=
.000001
 2.05x10-3=
.00205
Calculations
 (4x102)(2x103)=
 (4x102)/(2x10-4)=
8 x 105
2 x 106
Do you and your calculator have
a communication problem?
 Solve the problem below
using your calculator.
3.0x105
1.5x102 * 2.0x103
=
1
Measurements in Science
 Observations in science should be
quantified whenever possible.
For this reason, scientists (you) must
master the tools used for measuring and
the units that are used to express them.
The Importance of Units
 Numbers are used in science for
quantifying measurements.
 However, all numbers must be
followed by a unit!!
 Naked numbers have no meaning in
science! Thus will never receive full
credit!
General rules for
measurement
 All units will be metric. Memorize the
units for:
Length = meter (m)
mass = gram (g)
volume = liter (L)
***Important Note!! 1 mL = 1 cm3
Metric Prefixes
Metric Prefixes
Learning Check
Select the unit you would use to measure
1. Your height
a) millimeters
2. Your mass
b) meters
c) kilometers
a) milligrams
b) grams
c) kilograms
3. The distance between two cities
a) millimeters
b) meters
c) kilometers
4. The width of an artery
a) millimeters
b) meters
c) kilometers
Practice
1 kg =
g
1m =
cm
1 km =
m
1L =
mL
1 cm =
m
1 cm =
mm
1 mL =
L
Units of Length
 ? kilometer (km) = 500 meters (m)
 2.5 meter (m) = ? centimeters (cm)
 1 centimeter (cm) = ? millimeter (mm)
 1 nanometer (nm) = 1.0 x 10? meter
O—H distance =
9.4 x 10-11 m
9.4 x 10-9 cm
0.094 nm
The next several slides you
will solve on your white
board.
Write out all conversion
factors as ratios showing
unit cancellations.
When done hold it up for me
to evaluate.
What is the volume (in
liters) of a 500mL waterbottle?
A rattlesnake is 2.44 m long.
How long is the snake in
inches?
How fast in mi/hr is 22m/s?
The speed of sound is
about 343m/s. If you hear
thunder 3.0 seconds after
seeing lightning, how far
is the storm from you (in
miles)
PROBLEM: Mercury (Hg) has a
density of 13.6 g/cm3. What is the
mass of 65 mL of Hg in grams? In
pounds?