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Thursday, October 31, 2013



Happy Halloween!
Standard IE1: Scientific
progress is made by
asking meaningful
questions and
conducting careful
scientific experiments.
Independent Practice:


Section 3.3 Reading
Packet
Question: Copy the
chart into your Journal.
Quantity
SI Base
Unit
Symbol
Length
Meter
m
Mass
Kilogram
kg
Temp
Kelvin
K
Time
Second
s
Amount of
Substance
Mole
mol
Luminous
Intensity
Candela
cd
Electric
Current
Ampere
A
Measurements
and
Calculations
Units of Measurement
 Measurements
involve NUMBER and UNIT
 Represent a quantity: has magnitude, size,
or amount
 Gram = unit of measurement
 Mass = quantity
Units of Measurement
 Scientists
system…



around the world agree on one
International System of Units (le Systeme
International d’Unites)
SI units
Built from seven base units
SI Base Units
Units of Measurement
Units of Measurement
 Metric
Prefixes – make units easier to use
 Make the unit smaller or larger
 Unit = prefix + base unit
 Table pg. 74
Mass
 Measures
quantity of matter
 SI unit: kilogram, kg
 ______ kg = _____ g
 gram used for smaller masses
 Weight: measure of gravitational pull
Length
 SI
unit: meter, m
 Longer distances: kilometer, km
 _______ km = _______ m
 Shorter distances: centimeter, cm
 _______ m = ________ cm
Volume
 SI
unit: m3
 A derived unit: combination of base units by
multiplying or dividing
 SI unit for Area: l x w = m x m = m2
 Volume: l x w x h = m x m x m = m3
 Also: liters (L), mL, dm3 and cm3
 1 L = 1 dm3 = 1000mL = 1000 cm3
Derived Units
Scientific Notation
 Put
the numbers in the form
a x 10n
 a has one # to left of decimal
 If # is bigger than 1  + exponent
 If # is less than 1  - exponent
Scientific Notation
 Review:
Write in scientific notation or
standard notation.
a. 32,700
b. 0.0003412
c. 3.901 x 10-6
d. 4.755 x 108
Let’s Practice
Scientific Notation
Worksheet
Significant Figures (Sig Figs)
 How
many numbers mean anything?
 When we measure, we can (and do) always
estimate between the smallest marks.
1
2
3
4
5
Significant Figures (Sig Figs)
 Better
marks better estimate.
 Last number measured actually an
estimate
1
2
3
4
5
Rules for Significant Figures
1)
All nonzero digits are significant.
•
457 cm has 3 sig figs
•
2.5 g has 2 sig figs
2)
Zeros between nonzero digits are significant.
•
1007 kg has 4 sig figs
•
1.033 g has 4 sig figs
3)
Zeros to the left of the first nonzero digit are not significant. They are not actually
measured, but are place holders.
•
0.0022 g has 2 sig figs
•
0.0000022 kg has 2 sig fig
4)
Zeros at the end of a number and to the right of a decimal are significant. They are
assumed to be measured numbers.
•
0.002200 g has 4 sig figs
•
0.20 has 2 sig figs
•
7.000 has 4 sig figs
5)
When a number ends in zero but contains no decimal place, the zeros may or may
not be significant. We use scientific (aka exponential) notation to specify.
•
7000 kg may have 1, 2, 3 or 4 sig figs!
Sig Figs
 What
is the smallest mark on the ruler that
measures 142.15 cm?
 142 cm?
 140 cm?
 Does the zero mean anything? (Is it significant?)
 They needed a set of rules to decide which
zeroes count.
Sig Figs.
 405.0
g
 4050 g
 0.450 g
 4050.05 g
 0.0500060 g
Sig Figs
 Only
measurements have sig figs.
 Counted numbers are exact – infinite sig
figs
 A dozen is exactly 12
 Conversion factors: 100 cm = 1 m
Problems
 50
has only 1 significant figure
 if it really has two, how can I write it?
 Scientific notation
x 101
2 sig figs
 Scientific Notation shows ALL sig figs
 5.0
Rounding Rules
 Round



454.62 to four sig figs
to three sig figs
to two sig figs
to one sig fig
Sig Figs
 How
many sig figs in the following
measurements?
 458 g
 4085 g
 4850 g
 0.0485 g
 0.004085 g
 40.004085 g
Let’s Practice
Significant Figures
Worksheet
Journal - Thursday,
November 7, 2013



Standard IE1: Scientific progress is made by asking
meaningful questions and conducting careful scientific
experiments.
Independent Practice:
 Significant Figures Worksheet (#2)
Question: Copy the chart into your Journal. (next slide)
Prefix
Meaning
Factor
Mega (M)
1 million times
larger than unit
106
Kilo (k)
1,000 times larger
than unit
103
Deci (d)
10 times smaller
than unit
10-1
Centi (c)
100 times smaller
than unit
10-2
Milli (m)
1,000 times smaller 10-3
than unit
Micro (μ)
1 million times
smaller than unit
10-6
Nano (n)
1,000 million times
smaller than unit
10-9
Pico (p)
1 trillion times
smaller than unit
10-12
OPEN NOTE Quiz!!
 When?


Blocks 1 and 3:
Wednesday,
November 13,
2013
Blocks 2 and 4:
Thursday,
November 14,
2013
 Topics






Included:
SI Units
Scientific Notation
Significant Figures
Significant Figures
in Calculations
Density
Conversions
Vocabulary Review
 Calibration:
a set
of graduations to
indicate values or
positions.
 Precision: Describes
the closeness, or
reproducibility, of a
set of
measurements
taken under the
same conditions.
 Convey:
To make
something known
to someone.
 Significant: Very
important.
 Intervals: A period
of time between
events.
Review:
Scientific Notation
and Significant
Figures Worksheets
Calculations
with Significant
Figures Rules
Annotate the Reading
Calculations with Sig Figs
1.
2.
3.
165.86 g + 4.091g - 140 g + 27.32 g
(35.6 L + 2.4 L) / 4.083 =
2.524 x (16.408 m – 3.88 m) =
Answers: 57g
9.31 L 31.62 m
Let’s Practice
Significant Figures in
Calculations WS
Density
 Density
= mass
D=m
volume
V
 Units: g/cm3 or g/mL but SI unit is kg/m3
 derived unit
 Used to identify substances
 Varies with temperature
 As temp. increases density…
Density
Density Examples
 If
a metal block has a mass of 65.0 grams
and a volume of 22 cubic centimeters,
what is the density of the block?
D=m
V
 D = 65.0 g = 3.0 g/cm3
22 cm3
Density Examples
 Aluminum
has a density of 2.7 g/cm3.
What volume of aluminum has a mass of
60 grams?
D=M
V
20 cm3
Density Examples
 Gold
has a density of 19.3 g/cm3. A block
of metal has a mass of 80 g and a volume
of 12 cm3. Could this block be a piece of
gold?
 No, because this block has a density of 7
g/cm3s
Journal – Friday, November
8, 2013
 Standard:

IE1: Scientific progress is made
by asking meaningful
questions and conducting
careful experiments.
 Independent
Practice:

Revise Section 3.3
Reading Packet
 Calculate
the
Following (mind
your sig figs):


(3.2 + 4.55) x 12.4
(88.33-6.782) / 9
Review – Sig
Figs in
Calculations
Unit Conversions
Unit Conversions

1.
2.
3.
Given information in one unit  need to
find the equivalent in another unit
Identify what’s given
Organize plan of attack
Carry out plan WITH UNITS!!
Conversion factors
ratio of equivalent measurements.”
 Start with two things that are the same.
1 m = 100 cm
 Can divide by each side to come up with
two ways of writing the number 1.
 “A
Conversion factors
1m
100 cm
=
100 cm
100 cm
Conversion factors
1m
100 cm
=
1
Conversion factors
1m
100 cm
1m
1m
=
=
1
100 cm
1m
Conversion factors
1m
100 cm
1
=
=
1
100 cm
1m
Conversion Factors
 Unique
way of writing the number 1.
 Does NOT change the VALUE, it changes
the UNITS.
Write the conversion factors
for the following
 kilograms
to grams
 feet to inches
 1 L = 1 dm3 = 1000mL = 1000 cm3
Method for Converting
1.
2.
T-Chart or Factor Label Method
Steps:
1.
1. Draw a Great Big “T”
2.
2. Put the number the problem gives you to
convert to the top left of the “T”.
3.
3. Put the unit of that number in the bottom
right part of the “T”.
4.
4. Write the units of what you want in the top
right.
5.
5. Write the unit conversion factor in front of
the units from Steps 3 and 4.
Let’s Try Some!
 323
mm = _____ nm
 3.2 miles = _____ in
 250 gallons = _____ mL
 15 days = _______ min
More Unit
Conversions
More Involved
Derived Unit Conversions
 54.3
cm3 = ______ m3
 7.54
ft2 = _______ in2
Derived Unit Conversions
 125.3
m/s = ______ mi/hr
 625
g/mL = ______ kg/m3
 100
km/hr = ______ mi/hr
Let’s Practice
Dimensional Analysis
Where do
these
measurements
come from?
Recording Measurements
Making Good Measurements

1.
We can do 2 things:
Repeat measurement many times
- reliable measurements get the same number
over and over
- this is PRECISE
Making Good Measurements
2. Test our measurement against a
“standard”, or accepted value
- measurement close to accepted value is
ACCURATE
Measurements are Uncertain
1.
2.
3.
4.
Measuring instruments are never perfect
Skill of measurer
Measuring conditions
Measuring always involves estimation


Flickering # on balance
Between marks on instrument
Estimating Measurements
Error
 Probably
not EXACTLY 6.35 cm
 Within .01 cm of actual value.
 6.35 cm ± .01 cm
 6.34 cm to 6.36 cm
Calculating Percent Error
 Compares
your measurement to accepted
Valueexperimental -Valueaccepted
value
Percentage error =
× 100
Valueaccepted
 Negative
if measurement is small
 Positive if measurement is big
Calculating Percent Error
 What
is the % error for a mass
measurement of 17.7g, given that the
correct value is 21.2g?
Let’s Practice
Percent Error Worksheet