Transcript A. Why do scientists use the metric system?

Using the Metric System
A. Why do scientists use the metric system?
 The metric system was developed in France in
1795 - used in all scientific work because it has
been recognized as the world wide system of
measurement since 1960.


SI system is from the French for Le Systeme
International d’Unites.
The metric system is used in all scientific work
because it is easy to use. The metric system is
based upon multiples of ten. Conversions are
made by simply moving the decimal point.
What is the basic unit of length?
 The meter – a
little longer
than a yard
What do scientists use to measure the length
of an object smaller than a yard?
 A centimeter – one
hundredth of a
meter, so there are
100 centimeters in a
meter
 A millimeter – There
are 1,000 millimeters
in a meter
How do scientists measure long
distances?
 The kilometer –
There are
1,000 meters
in a kilometer
Which measurement to USE?
Base Units (Fundamental Units)
QUANTITY
NAME
SYMBOL
_______________________________________________
Length
meter
m
----------------------------------------------------------------------------Mass
gram
g
------------------------------------------------------------------------------Time
second
s
------------------------------------------------------------------------------Temperature
Kelvin
k
-------------------------------------------------------------------------------Volume(liquid)__________liter_____________L________________
SI Prefixes
Prefix Symbol Multiplication Factor
Term
Micro u
(0.000 001)
one millionth
Milli
m
(0.001)
one thousandth
Centi c
(0.01)
one hundredth
Deci
d
(0.1)
one tenth
One Unit
Deka dk
Hecto h
Kilo
k
Mega M
1
10
100
1000
1 000 000
one
ten
one hundred
one thousand
one million
Metric Units Used In This Class
QUANTITY
Length
NAME
meter
centimeter
millimeter
kilometer
SYMBOL
m
cm
mm
km
Mass
gram
kilogram
centigram
milligram
g
kg
cg
mg
Volume
liter (liquid)
milliliter (liquid)
cubic centimeter (solid)
L (l)
mL (ml)
cm3
Derived Units
 Base Units – independent of other units-measure
 Derived Units – combination of base units-calculated
Examples
 density  g/L mass / volume (grams per liter)
 volume  m x m x m = meters cubed
 Velocity  m/s (meters per second
SCIENTIFIC NOTATION

Scientific Notation: Easy way to express very large
or small numbers
A.0 x



10x
A – number with one non-zero digit before decimal
x -exponent- whole number that expresses the number
decimal places

if x is (-) then it is a smaller -left

if x is (+) than it is larger-right
PRACTICE
 Convert to Normal
 2.3 x 1023 m
3.4 x 10-5 cm
Convert to SN
3,400,000,
.0000000456
Multiplying
 Calculating in Scientific notation
 Multiplying

Multiple the numbers
Add the exponents
 (2.0 x 104) (4.0 x 103) = 8.0 x 107
Dividing


divide the numbers
subtract the denominator exponent from the numerator
exponent
 9.0 x 107
 3.0 x 105
3.0 x 102
Add
 Add or subtract



get the exponents of all # to be the same
calculate as stated
make sure the final answer is in correct scientific notation
form
 7.0 x 10 4 +
 7. 0 x 104
 70,000
3.0 x 10 3 =
+ .3 x 104 = 7.3 x 104
+ 3,000 = 73000= 7.3 x104
subtract
 7.0 x 10 4 - 3.0 x 10 3 =
 7.0x 104 – .30 x 104 = 6.7 x 104
 70,000 - 3 000 =67,000
PRACTICE










Add:
2.3 x 103 cm + 3.4 x 105 cm
Subtract:
2.3 x 103 cm - 3.4 x 105 cm
Multiply:
:
2.3 x 103 cm X 3.4 x 105 cm
Divide:
:
2.3 x 103 cm / 3.4 x 105 cm
Making Unit Conversions

Make conversions by moving the decimal point to the
left or the right using:
“ king henry died unit drinking chocolate milk”
Examples
1. 10.0 cm = __________m
2. 34.5 mL = __________L
3. 28.7 mg = __________kg
Factor label method /
Dimensional analysis










Use equalities to problem solve converting units.
quantity desired =
quantity given x conversion factor (equality)
A-given unit
B-desired unit
C-given unit
A x B
C
B
C must equal 1 use equality sheet
Equalities You Need To Know
1 km = 1000 m
1 m = 100 cm
1 m = 1000 mm
1L = 1000 mL
1kg = 1000g
1 g = 100cg
1 g = 1000 mg
ENGLISH TO METRIC
 1 inch=2.5 centimeters
 1 gal=3.8 liters
 1lb= 4.4 Newtons
 1qt = .94 Liters
 1 ft = .30 meters
 12 in = .30 meters
 1 mi = 1.6 Km
Four-step approach
When using the Factor-Label Method
it is helpful to follow a four-step approach
in solving problems:
1.What is question – How many sec in 56 min
2. What are the equalities- 1 min = 60 sec
3. Set up problem (bridges) 56 min 60 sec
1 min
4. Solve the math problem -multiple everything on top
and bottom then divide 56 x 60 / 1