Transcript scientific notation

Measuring in
Science
Metric System
Dimensional Analysis
Density
Scientific Notation
Sig Figs
Scientific Notation
• Numbers in science are often very large or
very small.
• To avoid confusion, we use scientific
notation.
• Scientific notation utilizes the numeric
digits in a measurement followed by a
power of ten.
• The numeric digits are expressed as a
number between 1 and 10.
Multiplying/Dividing with
Sci Notation
• When multiplying with sci notation, multiply
the base numbers and ADD exponents
• When dividing with sci notation, divide the
base numbers and SUBTRACT the
exponents
• There are 26,800,000 helium atoms in 1.00
L of helium gas. Express the number in
scientific notation.
A.
B.
C.
D.
26, 800,000 X 107
2.6800000 X 107
2.68 X 107
None of the above
0.0089. Express the number in
scientific notation.
A.
B.
C.
D.
.0089 X 103
8.9 X 103
8.900 X 103
None of the above
Conversion Factors
• A conversion factor takes the unit equation and
converts it into a ratio.
• For example, 2.2 cm= 1 inch, so…
• To convert 3 cm to inches, simply set up as
follows:
3 cm
1 in
2.2 cm
Dimensional Analysis (cont)
• To convert 3 inches to cm, simply set up
as follows:
3 in
2.2 cm
1 inch
If there are 2 googles in 4 blats, 1 google equals
_________ blats
2.0
0.1
• The mass of an object is a
measure of the amount of
matter it posses.
• Mass is measured with a
balance and is not affected
by gravity.
• Weight is the force exerted
by gravity on an object
• Mass and weight are not
interchangeable
• The SI unit for mass is the
kilogram (kg)
• 1 kg = 2.20 lb
M
a
s
s
Volume
• Volume is the amount of space
• occupied by matter.
• The SI unit for volume is the
cubic meter (m3)
• The metric unit (and the more
often used unit) is the liter (L)
• There are several instruments
for measuring volume
• 1 mL = 1 cm3
12.3 mL = _________cm3
12.3
0.0
Metric Conversions
• Kilo
–Hecto
• Deka
–M or L or g
»Deci
» centi
»
milli
3.50 mg =______g
.00350
0.0
Sig Figs
• Zeros found at the beginning of a number ARE
never significant.
• Therefore, 0.5 cm, 0.05 cm, and 0.005 cm all
have one significant digit.
• Zeros found at the end of a number with no
decimal point ARE NOT significant.
• Therefore, 50 cm, 500 cm, and 5000 cm all have
one significant digit.
• All other zeros are significant
• Therefore, 50.0 cm, 0.0500 cm, and 501cm all
have three significant digits.
How many sig figs are in
0.00230 ?
3
0.
Finding Density for a Regular Object
• 1.
– Use the balance to find the mass of the object. Record this value
on the "Density Data Chart."
• 2.
– Use the metric ruler to measure the length, width, height, or
diameter of the object. Record the values that apply to your
object.
• 3.
– Compute the volume of the object using the values determined
in step 2. Record the volume on the data chart.
• 4.
– Compute the density of the object by dividing the mass value by
the volume value. Record the density on the data chart.
•
If the volume of an object is 4
mL, and the mass is 2 g, what is
the density of the object? (don’t
worry about units)
.5
0.1
Finding Density for an Irregular Object
• 1.
– Use the balance to find the mass of the object. Record the value on the
"Density Data Chart."
• 2.
– Pour water into a graduated cylinder up to an easily-read value, such as
50 milliliters and record the number.
• 3.
– Drop the object into the cylinder and record the new value in millimeters.
• 4.
– The difference between the two numbers is the object's volume.
Remember that 1 milliliter is equal to 1 cubic centimeter. Record the
volume on the data chart.
• 5.
– Compute the density of the object by dividing the mass value by the
volume value. Record the density on the data chart.