Opener #7 - WED - AUGUST 29, 2012 Pick up calculator.
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Transcript Opener #7 - WED - AUGUST 29, 2012 Pick up calculator.
Opener #7 - WED - AUGUST 29, 2012
Pick up calculator. Have out Notes ch. 2 packet.
1. What are the base SI units for time, length, mass, and
temperature?
2. How many grams are in 45 kilograms?
3. How many quarters are in $50?
4. What is the volume of an unknown sample that has a
density of 0.5 g/mL and a mass of 2.0 grams.
CW: Class Notes 2.2C-2.3 Using Dimensional Analysis
for Conversions, Accuracy vs. Precision, % Error, AND
Significant Figures.
HW: Study Guide Questions are due Friday
TEST Unit 1 (ch.1-2) is WED. Sept. 5th. STUDY!!!!
Turned in the 2 lab sheets yesterday if absent..
Chapter menu
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Opener #8 - THURS - JAN. 17, 2013
Pick up calculator. Have out Notes ch. 2 packet.
Pick up opener #8 half-sheet handout for Significant
figures and get out your notes packet to be ready to
start.
CW: Class Notes 2.2C-2.3 Using Dimensional Analysis
for Conversions
CW: Dimensional Analysis worksheet - use T-chart
method and turn in with lab sheet on other side when
done.
HW: Study Guide Questions due tomorrow but will not be
counted as grade until next week. Come with
questions and have all of the questions answered that
you can.
TEST Unit 1 (ch.1-2) is WED. JAN. 23rd - STUDY!!!!
Turned in the first lab sheets yesterday
Chapter menuif absent..
Resources
MAKE UP for 2 LABs today after class ONLY TODAY!
Copyright © by Holt, Rinehart and Winston. All rights reserved.
2.2C
Conversion Problems using
Dimensional Analysis
Because each country’s
currency compares differently
with the U.S. dollar, knowing
how to convert currency units
correctly is very important.
Conversion problems are
readily solved by a problemsolving approach called
dimensional analysis.
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2.2C
Conversion Problems
>
Conversion Factors
Conversion Factors
What happens when a measurement
is multiplied by a conversion factor?
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© Copyright Pearson Prentice Hall
End Show
2.2C
Conversion Problems
>
Conversion Factors
A conversion factor is a ratio of equivalent
measurements.
The ratios 100 cm/1 m and 1 m/100 cm are
examples of conversion factors. They are equal to 1.
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Chapter 2
Section 2 Units of Measurement
Conversion Factors
• A conversion factor is a ratio derived from the
equality between two different units that can be used
to convert from one unit to the other.
• example: How quarters and dollars are related
4 quarters
1
1 dollar
1 dollar
1
4 quarters
0.25 dollar
1
1 quarters
1 quarter
1
0.25 dollar
Chapter menu
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Chapter 2
Visual Concepts
Conversion Factor
Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/stu
Visual Concept
dent/ch02/sec02/vc03/hc602_02_v03fs.htm
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Chapter 2
Section 2 Units of Measurement
Conversion Factors, continued
• Dimensional analysis is a mathematical technique
that allows you to use units to solve problems
involving measurements.
• quantity sought = quantity given conversion factor
• example: the number of quarters in 12 dollars
number of quarters = 12 dollars conversion factor
4 quarter
? quarters 12 dollars
48 quarters
1 dollar
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2.2
Conversion Problems
>
Conversion Factors
When a measurement is multiplied by
a conversion factor, the numerical
value is generally changed, but the
actual size of the quantity measured
remains the same.
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METRIC CONVERSION PROBLEM ACTIVITY
CLICK HERE TO SEE CONVERSION FACTOR
PROBLEM ACTIVITY
I will make up own problem if teacher leading notes such
as how many seconds have you been alive after doing
a few easier examples.
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CH. 2 - MEASUREMENT
III. Unit Conversions
I
(Modern Chemistry Holt p. 40 - 42)
II
III
C. Johannesson
A. SI Prefix Conversions
532 m
NUMBER
UNIT
0.532 km
= _______
=
NUMBER
UNIT
B. Dimensional Analysis
The “Factor-Label” Method (also
called Dimensional Analysis)
Units, or “labels” are canceled, or
“factored” out
B. Dimensional Analysis
Steps:
1. Identify starting & ending units.
2. Line up conversion factors so units
cancel.
3. Multiply all top numbers & divide
by each bottom number.
4. Check units & answer.
B. Dimensional Analysis
Lining up conversion factors:
1 in = 2.54 cm
=1
2.54 cm 2.54 cm
1 in = 2.54 cm
1=
1 in
1 in
B. Dimensional Analysis
Convert 4432 mm to km.
mm
km
4432 mm
1m
1 km
1000 mm 1000 m
=0.004432 km
B. Dimensional Analysis
Study this before trying the next
problems. How many milliliters are in
1.00
quart
of
milk?
Reference
shows
qt
mL
1.057 qts = 1 L
1.00 qt
1L
1000 mL
1.057 qt
1L
= 946 mL
B. Dimensional Analysis
#1) You have 1.5 pounds of gold.
Find its volume in cm3 if the density
of gold is 19.3 g/cm3. (2.2 pounds = 1
lb kg)
cm3
1.5 lb 1 kg 1000 g 1 cm3
2.2 lb
1 kg
19.3 g
= 35 cm3
B. Dimensional Analysis
#2) How many liters of water would fill
a container that measures 75.0 in3?
in3
L
75.0 in3 (2.54 cm)3
(1 in)3
1L
1000 cm3
= 1.23 L
B. Dimensional Analysis
#3) Your European hairdresser wants
to cut your hair 8.0 cm shorter. How
many inches will he be cutting off?
cm
in
8.0 cm 1 in
2.54 cm
= 3.1 in
B. Dimensional Analysis
#4) Taft football needs 550 cm for a
1st
down. How many yards is
this?
cm
550 cm
1 in
1 ft 1 yd
2.54 cm 12 in 3 ft
= 6.0 yd
yd
B. Dimensional Analysis
#5) A piece of wire is 1.3 m long. How
many 1.5-cm pieces can be cut from
this wire?
m
1.3 m
pieces
100 cm
1 piece
1m
1.5 cm
= 86 pieces
- THURS - JAN. 17, 2013
ASSIGNMENTS
CW: Dimensional Analysis worksheet - use T-chart
method and turn in with lab sheet on other side when
done.
HW: Study Guide Questions due tomorrow but will not be
counted as grade until next week. Come with
questions and have all of the questions answered that
you can.
TEST Unit 1 (ch.1-2) is WED. JAN. 23rd - STUDY!!!!
Turned in the first lab sheets yesterday if absent..
MAKE UP for 2 LABs today after class ONLY TODAY!
Catch up on Notes 2.1-2.3 if you have been absent after
doing the Dimensional Analysis sheet.
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2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
Accuracy, Precision, and Error
How do you evaluate accuracy and
precision?
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2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
Accuracy and Precision
• Accuracy is a measure of how close a
measurement comes to the actual or true
value of whatever is measured.
• Precision is a measure of how close a
series of measurements are to one another.
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2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
To evaluate the accuracy of a
measurement, the measured value
must be compared to the correct
value. To evaluate the precision of a
measurement, you must compare the
values of two or more repeated
measurements.
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2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
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© Copyright Pearson Prentice Hall
End Show
Chapter 2
Section 3 Using Scientific
Measurements
Accuracy and Precision
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Chapter 2
Visual Concepts
Accuracy and Precision
Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/st
Visual Concept
udent/ch02/sec03/vc00/hc602_03_v00fs.h
tm
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2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
Just because a measuring device works, you
cannot assume it is accurate. The scale below
has not been properly zeroed, so the reading
obtained for the person’s weight is inaccurate.
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End Show
2.3
Measurements and Their
Uncertainty
>
Accuracy, Precision, and Error
Determining Error
• The accepted value is the correct value
based on reliable references.
• The experimental value is the value
measured in the lab.
• The difference between the experimental
value and the accepted value is called the
error.
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End Show
Chapter 2
Section 3 Using Scientific
Measurements
Accuracy and Precision, continued
Percentage Error
• Percentage error is calculated by subtracting the
accepted value from the experimental value, dividing
the difference by the accepted value, and then
multiplying by 100.
Percentage error =
Valueexperimental -Valueaccepted
Valueaccepted
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Chapter 2
Section 3 Using Scientific
Measurements
Percentage Error
Visual Concept
Click below for Visual Concept
Click for Visual Concept on Percent
Error
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PERCENT ERROR PROBLEM ACTIVITY
CLICK HERE FOR PERCENT ERROR PROBLEM
ACTIVITY
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Opener #8 - THURSDAY - AUGUST 30, 2012
1. Using Dimensional Analysis, show the age of a 16 year
old student whose birthday is today at this exact moment
in the number of seconds the student has been alive.
2. Describe the difference between precision and accuracy
in your own words.
3. Convert 5.4 feet to millimeters showing all work with
Dimensional Analysis. (2.54 cm = 1 inch)
CW: Notes Significant Figures
CW: Bingo Game CW: If time, metric puzzle game
HW: Study Guide questions due tomorrow; TEST 9/5 WED
HW/CW: Pre-lab side of w/sheet - due tomorrow
- other side dueTuesday
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B. Dimensional Analysis
#1)Show the age of a 16 year old student
whose birthday is today at this exact moment
in the number of seconds the student has
been alive.
years
16 yrs
seconds
365.25days
1 yr
24 hrs
60 min
1 day
1 hr
60 sec
= 504,921,600 s
1 min
B. Dimensional Analysis
3. Convert 5.4 feet to millimeters
showing all work with Dimensional
Analysis.
ft
–
(2.54 cm = 1 inch)
mm
5.4 ft 12 in 2.54 cm 10 mm
= 1646 mm
1 ft
1 in
1 cm Sig. Fig.
1600 mm
Chapter 2
Section 3 Using Scientific
Measurements
Accuracy and Precision, continued
Problem Example - RECORD in notes before
checking.
A student measures the mass and volume of a
substance and calculates its density as 1.40 g/mL. The
correct, or accepted, value of the density is 1.30 g/mL.
What is the percentage error of the student’s
measurement?
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Chapter 2
Section 3 Using Scientific
Measurements
Accuracy and Precision, continued
Sample Problem C Solution
Percentage error =
Valueexperimental -Valueaccepted
Valueaccepted
100
1.40 g / mL - 1.30 g / mL
100 7.7%
1.30 g / mL
= 7.69% Sig.Fig.
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Chapter 2
Section 3 Using Scientific
Measurements
Accuracy and Precision, continued
Error in Measurement
• Some error or uncertainty always exists in any
measurement.
• skill of the measurer
• conditions of measurement
• measuring instruments
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Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures
• Significant figures in a measurement consist of all
the digits known with certainty plus one final digit,
which is somewhat uncertain or is estimated.
• The term significant does not mean certain.
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Chapter 2
Section 3 Using Scientific
Measurements
Sig. figs. in a
measurement
include the
known digits
plus a final
estimated digit
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Chapter 2
Visual Concepts
Significant Figures
Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/student/
Visual Concept
ch02/sec03/vc02/hc602_03_v02fs.htm
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Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures, continued
Determining the Number of Significant Figures
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Chapter 2
Visual Concepts
Rules for Determining Significant Zeros
Click below to watch the Visual Concept.
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Visual Concept
2/sec03/vc03/hc602_03_v03fs.htm
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C. Significant Figures
Counting Sig Fig Examples
1. 23.50
4 sig figs
2. 402
3 sig figs
3. 5,280
3 sig figs
4. 0.080
2 sig figs
Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures, continued
Sample Problem D
How many significant figures are in each of the
following measurements?
a. 28.6 g
b. 3440. cm
c. 910 m
d. 0.046 04 L
e. 0.006 700 0 kg
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Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures, continued
Sample Problem D Solution
a. 28.6 g
There are no zeros, so all three digits are significant.
b. 3440. cm
By rule 4, the zero is significant because it is
immediately followed by a decimal point; there are 4
significant figures.
c. 910 m
By rule 4, the zero is not significant; there are 2
significant figures.
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Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures, continued
Sample Problem D Solution, continued
d. 0.046 04 L
By rule 2, the first two zeros are not significant; by
rule 1, the third zero is significant; there are 4
significant figures.
e. 0.006 700 0 kg
By rule 2, the first three zeros are not significant;
by rule 3, the last three zeros are significant; there
are 5 significant figures.
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OPENER #10 - TUESDAY, JANUARY 22, 2013
Write the number and the answer. Pick up calculator.
SIG. FIG. PRACTICE QUESTIONS
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SIG. FIG. ANSWERS - CHECK WORK
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Chapter 2
Section 3 Using Scientific
Measurements
Significant Figures, continued
Rounding
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Chapter 2
Visual Concepts
Rules for Rounding Numbers
Click below to watch the Visual Concept.
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Visual Concept
x/student/ch02/sec03/vc04/hc602_03_
v04fs.htm
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C. Significant Figures
Calculating with Sig Figs
Multiply/Divide - The # with the fewest
sig figs determines the # of sig figs in
the answer.
(13.91g/cm3)(23.3cm3) = 324.103g
4 SF
3 SF
3 SF
324 g
C. Significant Figures
Calculating with Sig Figs (con’t)
Add/Subtract - The # with the lowest
decimal value determines the place of
the last sig fig in the answer.
3.75 mL
+ 4.1 mL
7.85 mL 7.8 mL
224 g
+ 130 g
354 g 350 g
C. Significant Figures
Calculating with Sig Figs (con’t)
Exact Numbers do not limit the # of sig
figs in the answer.
Counting
Exact
“1”
numbers: 12 students
conversions: 1 m = 100 cm
in any conversion: 1 in = 2.54 cm
C. Significant Figures
Practice Problems
f). (15.30 g) ÷ (6.4 mL)
4 SF
2 SF
= 2.390625 g/mL 2.4 g/mL
2 SF
g). 18.9 g
- 0.84 g
18.06 g 18.1 g
ASSIGNMENTS
*Have out study guide questions.
*Complete dimensional analysis
problems and turn in box no later
than tomorrow.
*Finish measurement questions and
turn in box no later than tomorrow.
*Start computer game review to help
with test; also available from home.
TEST ch.1-2 is on Thursday!
OPENER #8 - FRIDAY - 8/31/12
Opener - pre-lab sheet from yesterday
side 1 only. Side 2 is homework due
Tuesday.
*Pick up lab data recording sheet &
procedure sheet. (2 sheets for lab)
*Pick up calculator. Have out S.GUIDE
*Picture packets (juniors - 1st block)
*CW: Measurement Lab (stations)
*TEST - THURS 9/6/12 ch. 1-2
OPENER #9- FRIDAY - 1/18/2013
Opener - sig.fig. quiz handout - turn
over when done & work on DA sheet.
*Pick up lab data recording sheet &
procedure sheet. (2 sheets for lab)
*CW: Dimensional Analysis w/sheet
turn in when completed.
*Pick up review game sheet. See me
when ready.
*Pick up calculator. Have out S.GUIDE
D. Scientific Notation - did
with Bingo
65,000 kg 6.5 × 104 kg
Converting into Sci. Notation:
Move decimal until there’s 1 digit to its
left. Places moved = exponent.
Large # (>1) positive exponent
Small # (<1) negative exponent
Only include sig figs.
OPENER #10 - MON SEPT 4, 2012
Pick up calculator & computer & handout.
Rewrite each to scientific notation or standard
form.
1.
2,400,000
g
2.
2.4
6
10
g
2.56 10-3 kg
0.00256
kg
0.00007 km
62,000 mm
Turn in side 2 of opener sheet from Friday. (conversion questions).
-5
HW:
Measurement Lab due tomorrow.
3.
7 10
ASSIGNMENTS MON 9-4-12
*Turn in the homework conversion from
Friday (back of opener) IN BOX.
CW/HW: Computer Lab Activities Game
due tomorrow if not finished in class.
HW: Measurement Lab due tomorrow.
HW: Study for TEST on THURSDAY
due to School Pictures tomorrow
Ch.1-2 Test is Thursday! Be well
prepared & Make an A!
D. Scientific Notation
Calculating with Sci. Notation
(5.44 × 107 g) ÷ (8.1 × 104 mol) =
Type on your calculator:
5.44
EXP
EE
7
÷
8.1
EXP
EE
4
EXE
ENTER
= 671.6049383 = 670 g/mol = 6.7 × 102 g/mol
Stop here and play BINGO GAME ACTIVITY
HW: Study Guide Questions due on Friday.
Get out a sheet of paper and make a 5 x 5 grid. (5 rows
and 5 columns)
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OPENER #11 - WEDNESDAY, SEPTEMBER 5, 2012
1. How many significant figures do these have?
A. 200 mL B. 0.02 mL C. 20.2 mL D. 200.0 mL
2. Calculate the Percentage Error for a mass measurement of
17.7 g given that the correct value is 21.2 g. Show your
work even if using calculator.
CW: Turn in Measurement Lab from last Friday data sheet,
conversion calculations with T-charts showing
dimensional analysis and pre-lab with instruction sheet
stapled together IN BOX.
*Also turn in conversion homework with opener #9 sheet if
not done yesterday.
*CW: Compete 3.1 Notes & Computer Review Activity Games
TEST is tomorrow over ch.1-2 - BE WELL PREPARED!!!!!
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THURSDAY, SEPTEMBER 6, 2012
*Have out openers, Notes packets ch.1 & 2, and Bingo
Game, quick salt-egg water lab questions, and
computer review game sheet to turn in. I will pick these
up and staple while you get ready to start your test.
*Have out notebook sheet of paper with your name on it
and TEST ch.1-2 Part 2 as title.
*Have out pencil or blue/black pen and calculator.
*Pick up computer and log-in to the podcast page.
*Download test & reference sheet - #1-60 on computer
AND #61-75 on notebook paper.
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