Ch 2 Measurements SI

SCIENTIFIC MEASUREMENT
Ch 2
Chemistry is a lot of math!
Warm-ups
8/22/13
Name
Per, Row
1.
2.
8/26/13
Saving paper is always
good!
WARM UP
1.Name 3 tools used for measurement.
2.What is a unit?
3.Give an example of a unit.
4.Why are units important.
MAKING MEASUREMENTS
Ch 2.2
Qualitative measurements: Give results in a
descriptive and non-numerical form
Example: Cookie Monster is Blue
Quantitative measurements: Give results in a
definite form – usually as numbers and units
Example: Cookie Monster ate 1 kg of cookies
QUALITATIVE OR QUANTITATIVE?
The Big Mac is $2.29.
The Pop Rocks are blue.
The coffee is hot.
The slurpee is 0 degrees Celsius.
Measurement—a quantity that has both a
number and a unit.
For example…
I weigh 90!
I make 1000 an hour!
There are 72 in this class.
Numbers with NO units mean NOTHING…and will
be marked WRONG on HW/Tests, etc.
Measurements are fundamental to the
experimental science.
INTERNATIONAL SYSTEM OF UNITS
SI UNITS (SYSTEME INTERNATIONALE)
Meter (m) for length
Use a
Second (s) for time
meterstick to measure
 Use a stopwatch to measure
Kilogram (kg) for mass
(1 kg = 2.2 lbs)
Mole for the amount of
substance
 Weight is NOT the same thing as
mass!
 Use a scale to measure
 We will talk about mole later
Kelvin (K) for temperature
 K = oC + 273
 0 K = absolute zero
 Use a thermometer to measure
 oC is another option, but not
Fahrenheit (in the metric
Liter (L) or m3 for volume
 Use a graduated cylinder to
measure 1L = 1m3
joule or calorie for
energy
 We don’t discuss this much in
this class…
MASS VS WEIGHT
Mass: amount of
matter
- Gravity does not
affect mass
Weight: measure
of gravitational pull
DERIVED UNITS: IT IS A COMBINATION OF UNITS
Volume: cm3
Density: D= m/v
amount of space Ratio of mass to
occupied by an
volume
object
Speed: meters/ second
WARM-UP
A scientist wants to conduct an experiment measuring
the effect of temperature on the density of nitrogen gas.
1. What is the independent variable in this experiment?
2. The dependent variable?
3. What could be used as a control group?
4. What would be some constants?
5. What units should be used for temperature and
density?
6. What tools should be used to measure temperature
and density?
METRIC PREFIXES
Adding prefixes, gives us a range of size
measurements.
Based on a system of 10’s (decimal system)
NOTE that the bigger number goes with the
smaller unit.
100 cm = 1 m
Prefixes you need to memorize…
milli- (1/1000), centi-(1/100), kilo(1000x)
METRIC
PREFIXES:
The metric system
utilizes prefixes
based on powers of
10.
Prefixes you need to
memorize…
milli(1/1000x),
centi-(1/100x),
kilo-(1000x)
ALL METRIC UNITS INCREASE OR DECREASE BY
A POWER OF 10.
Conversion factors: a ratio of equal proportions
Values can often be expressed in more than one form
$1 = 4 quarters = 10 dimes = 20 nickels = 100
pennies
1 meter = 100cm = 1000mm = 0.001km
equal values can be shown as a ratio equal to 1; such
ratios are called conversion factors…
$1
1000m
1km
60min
10 dim es
1hr
1km
1000m
conversion factors are useful for solving
problems in which given measurements
must be expressed in some other unit.
Example 1: conversions
a. convert 20 meters to to millimeters
1. which is smaller?
1000 mm in 1m
2. how many of the smaller are in the larger?
20,000mm
3. create a conversion
Example 2: conversions
b. Convert 20 meters to kilometers
0.02 km
Date SI Unit Practice
Convert each of the following:
Example: 3.68kg * 1000g
1. 3.68 kg = __________ g
1 kg
2. 568 cm = __________ m
3.68kg * 103
3. 8700 ml = __________ l
4. 25 mg = __________g
5. 0.101 cm = __________ mm
6. 250 ml = __________ l
7. 600 g = __________ kg
8. 8900 mm = __________ m
9. 0.000004 m = __________ mm
10. 0.250 kg = __________ mg
=
3680g
Use table 2 on pg35!
However you won’t get the table for your quiz next class
Date: SI Unit Practice
What SI unit would you use to measure….
1. The length of a
football field?
2. The WIDTH of a strand
of hair?
3. The mass of an
elephant?
4. The mass of an ant?
5. The distance from
school to Sears?
6. The height of your
desk?
7. The volume of water
in a pool?
8. The volume of water
in a spoon?
9. The temperature of
this room?
1. 3.68 kg = __3680____ g
2. 568 cm = ___5.68___ m
3. 8700 ml = ___8.7____ l
4. 25 mg = __0.025___ g
5. 0.101 cm = ___1.01___ mm
6. 250 ml = __0.25_____ l
7. 600 g = ___0.6____ kg
8. 8900 mm = ___8.9____ m
9. 0.000004 m = __0.004___ mm
10. 0.250 kg = __250000__ mg
What SI unit would you use to measure….
5. The distance from school
1. The length of a
to union station?
football field?
Meters
Kilometers
2. The WIDTH of a strand
of hair? Mm, um
3. The mass of an
km
elephant?
4. The mass of an ant?
Mg (grams)
6. The height of your desk?
cm
7. The volume of water in a
pool? kL or km3
8. The volume of water in a
spoon? mL or cm3
9. The temperature of this
room? Kelvin (Celsius)
SCIENTIFIC NOTATION: move decimal point the number of times
ex: 1*105
indicated by the power of 10.
+ means larger number
- means smaller number
Convert the following
out of or into
scientific notation
1) 6.5*104 =
65000.
2) 6.5*10-4 = .00065
3) .00035 =
3.5*10-4
4) 35000 =
3.5*104
DERIVED UNITS: IT IS A COMBINATION OF UNITS
Volume: cm3
amount of space
occupied by an
object
Density: D= m/v
Ratio of mass to
volume
mL=cm3
Speed: meters/ second
DENSITY
add the symbols <,
>, or =to compare
the blocks
<
<
=
DENSITY: D= M/V
Ex: A rock has a
mass of 10 grams
and a volume of 5
cm3. Calculate
its density.
10g / 5cm3
= 2 g/cm3
mass
Density 
volume
Units:
g
3
cm
g
mL
or
D= m/v
How can you find density from a
graph?
Density is the slope of the line
of mass vs volume.
y2- - y1
rise
D= m/v=slope =
= X –x
2
1
run
Ex: 11-3 g
= 1 g/mL
11-3mL
g
mL
1. What mineral is more dense?
A, B, or C?
- A: it has greatest slope
2. If you put equal volumes of A
and B on a balance, which
would have a larger mass?
-A
http://www.youtube.com/watch?v=-CDkJuo_LYs
DENSITY CALCULATIONS
Water displacement is used to find the volume of
unusual shape:
1. measure volume of water
50mL
2. Add an object and measure volume again
60ml
3. Subtract the volume of object+water from volume
of just water
60-50=10mL
Ex 2. The mass of 10 copper coins is 30 grams. The
initial volume of water is 50mL and the volume with
the coins if 55mL. Calculate the density of the copper
coins.
Ex: 3. The density of silver is 10.0 g/cm3. If you have a
sample size of 17.235 grams, what is the volume of
the silver?
HOW WOULD TEMP AFFECT DENSITY??
As temperature increases, what happens to
density?
If density deals with mass and volume…
Does temperature affect mass? Or volume?
HOMEWORK
HW: ch. 2 section 2
pg 42 answer
questions 1-6
Pg 881 #1, 2, 7
Quiz! Next class
Use pg 42 #1,2
And 881 # 1, 2, 7,
9 to study
Table on pg 35
1. The density of silver is
10.0 g/cm3. If you
have a sample size of
17.235 grams, what is
the volume of the
silver?
2. If you have equal
volumes of B(blue line)
and C (red line). Which
one has a larger mass?
CH 2.3
Accuracy:
the closeness of
measurements to the
actual value
Precision:
The closeness of a set
of measurements to
each other
2 technicians measure the density of a new substance:
A: 2.000, 1.999, and 2.001 g/mL
B: 2.5, 2.9, and 2.7 g/mL
The correct value is 2.480 g/mL
Who is more accurate and who is more precise?
PERCENT ERROR: MEASURE OF HOW DIFFERENT YOUR VALUE IS
FORM THE REAL VALUE
Percent error =
Value experimental – Value accepted *100%
Value accepted
Example:
The density of water at 4 oC is known to be 1.00 g/mL.
Kayla experimentally found the density of water to be
1.075 g/mL. What is her percent error?
SIGNIFICANT FIGURES
Ch 2.3
When we make quantitative
measurements, we care about how
good our data is.
How we do this? Significant figures
Slide 1 of 6
Significant Figures (Sig. Figs)
in Measurements…
Significant Figures: all the digits in a measurement
that are known with certainty plus one estimated
digit
Rules for Significant Figures:
1. Zeros b/t nonzero digits are significant
2. Zeros appearing in front of all nonzero are
not significant
3. Zeros at the end of a number and the right
of a decimal point are significant
4. Zeros at the end of a number but to the left
of a decimal point, if a decimal point is
there, are significant. (NOT necessarily
significant if no decimal)
Examples:
3
40.7 L
87009 km 5
.00958 m 3
1
0.09 kg
85.00g
9.00000
2000 m
2000. m
4
6
1
4
WHEN GIVEN A NUMBER, YOU MUST BE ABLE TO
D E T E R M I N E T H E N U M B E R O F S I G . F I G S . I N I T.
a) 12,389 = _____
e) 6.700 x 107 = _____
 All non-zero #’s are significant
 All numbers in the coefficient
of a # in scientific notation are
significant
b) 0.452 = _____
 Zeros before a decimal are not
imp unless it is part of a whole
number
c) 10.26 = _____
 zeros in between #’s are
significant
d) 23.000 = _____
 Zeros after a decimal are
significant IF THERE IS A
WHOLE #
f) 24,000,000 = _____
 zeros w/out a decimal are NOT
significant
 Perfect example of why sci.not.
is so great…gets rid of insig 0’s
g) 0.00000670 = _____
 zeros after a decimal but with
no whole # are NEVER
significant.
 Again, use sci.not.
MATH WITH SIG FIGS
Conversions with Sig Figs: use same number of
sig figs in the original measurement
- the conversion factor is considered exact and does not count
4.608 m * 100cm
m
=460.8cm
Addition and Subtraction with Sig Figs: answer
must have same # of sig figs as the number
with the fewest digits to right of the decimal
25.1g + 2.03g = 27.1g
Multiplication and Division with Sig Figs:
answer must use same # sig figs as the #
with the fewest sig figs
3.05g / 8.47mL = 0.360g
80.0g/ 5mL =
16mL = 20mL
80.0g/ 5.0mL = 16mL
SCIENTIFIC NOTATION: move decimal point the number of times
ex: 1*105
indicated by the power of 10.
+ means move to the right
- means move to the left
6.5*104 =
65000.
6.5*10-4 =
.00065
.00035 =
3.5*10-4
35000 =
3.5*104
Significant Figures
A. State the number of significant digits in each
measurement.
1)
2)
3)
4)
5)
6)
2804 m
2.84 km
5.029 m
0.003068 m
4.6 x 105 m
4.06 x 10-5 m
7) 750 m
8) 75 m
9) 75,000 m
10) 75.00 m
11) 75,000.0 m
12) 10 cm
Significant Figures Practice
A. State the number of significant digits in each
measurement.
1)
2)
3)
4)
5)
6)
2804 m 4
2.84 km 3
5.029 m 4
0.003068 m 4
4.6 x 105 m 2
4.06 x 10-5 m 3
8) 75 m
2
9) 75,000 m
2
10) 75.00 m
4
11) 75,000.0 m 6
12) 10 cm 1 or
2
7) 750 m
2 or 3
B. Solve the following problems and report answers
with appropriate number of significant digits.
1)
6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =
2) 1.6 km + 1.62 m +1200 cm =
3) 8.264 g - 7.8 g =
4) 10.4168 m - 6.0 m =
5) 12.00 m+15.001 kg=
6) 1.31 cm x 2.3 cm =
7) 5.7621 m x 6.201 m =
8) 20.2 cm / 7.41 s =
9) 40.002 g / 13.000005 g =
1)
6.201 cm + 7.4 cm + 0.68 cm +12.0 cm = 26.3 cm
2) 1.6 km + 1.62 m +1200 cm = 1.2 x 103 or 1.20 x 103 or
1203 m
3) 8.264 g - 7.8 g = 0.5 g
4) 10.4168 m - 6.0 m = 4.4 m
5) 12.00 m+15.001 kg= can’t add m and kg
6) 1.31 cm x 2.3 cm = 3.0 cm2
7) 5.7621 m x 6.201 m = 35.73 m2
8) 20.2 cm : 7.41 s = 2.73 cm/s
9) 40.002 g : 13.000005 g = 3.0771
WARM UP
1.
2.
3.
4.
What tool would you use to measure mass?
What unit would you use to measure mass?
What tool would you use to measure volume?
What unit(s) would you use to measure
length?
1. LINEAR MEASUREMENTS
The length, width, or height of something
Tool?
ruler, meter stick, etc.
Units?
 Meter (m)
 Centimeters (cm)
 Millimeters (mm)
PRACTICE:
2. VOLUME
The space matter takes up
Tool?
Graduated cylinder, beaker, etc.
Units?
Liter (L)
Milliliters (mL)
cm3
MUST BE EYELEVEL TO MEASURE CORRECTLY!
PRACTICE:
3. MASS
The quantity of matter
Tool?
balance, scale, etc.
Units?
Kilograms (kg)
Grams (g)
We use digital scales (usually)…so just record
what the scale says
Mass continued…
Scale must read zero before you place anything
on it!
If you want to measure the mass of something
inside a container…you must measure the
empty container first.
How much mass does the
water have?
462.3 g
450.0 g
4. TEMPERATURE
The amount of heat present
Tool?
thermometer
Units?
Degrees Celsius (°C)
5. DENSITY?
The amount of matter in a space
Units?
g/cm3 or g/mL
Tool?
scale and
ruler or graduated cylinder