Transcript Science

Integ. Science
Location
Due Date
Textbook/
Notebook
Today
Textbook/
Notebook
Tuesday
Metric Homework part 1
Worksheet
Worksheet
Tuesday
Metric Homework part 2
Worksheet
Wednesday
Assignments
Take Notes &Define Key Terms
on 2 – 26
Read/Use Appendix B
p. A8
Precision and Accuracy
Precision indicates degree of reproducibility of
a measured number.
Accuracy indicates how close your
measurements are to the true value.
Precision and Accuracy
When making measurements in science you
want them to be both precise and accurate.
SI Base Units
Physical Quantity
Time
Length
Temperature
Mass
Volume
Amount
Unit (standard)
Symbol
SI Base and Derived Units
Physical Quantity
Base Unit
Symbol
length
meter
m
area
square meter
m2
mass
kilogram
kg
volume
liter
l
density
gram/liter
g/l
temperature
degrees Celsius
°C
thermodynamic temperature
kelvin
K
time
second
s
electric current
ampere
A
amount of substance
mole
mol
luminous intensity
candela
Cd
Metric System
Designed during the French Revolution of
the 1790's, the metric system brought
order out of the conflicting and confusing
traditional systems of weights and
measures then being used in Europe.
Prior to the introduction of the metric
system, it was common for units of length,
land area, and weight to vary, not just from
one country to another but from one region
to another within the same country.
Metric System
• The metric system replaces all the traditional units, except the units
of time and of angle measure, with units satisfying three conditions:
• (1) One fundamental unit is defined for each quantity. These units
are now defined precisely in the International System of Units.
• (2) Multiples and fractions of these fundamental units are created by
adding prefixes to the names of the defined units.
• (3) The fundamental units are defined rationally and are related to
each other in a rational fashion.
• The metric units were defined in an elegant way unlike any
traditional units of measure. The Earth itself was selected as the
measuring stick. The meter was defined to be one ten-millionth of
the distance from the Equator to the North Pole
Mega
*****
*****
kilo
hecto
deka
BASE UNIT
deci
centi
milli
*****
*****
micro
Metric System
Prefixes
giga – G
1,000,000,000
mega – M
1,000,000
kilo – k
1,000
hecto – h
100
deka – da
10
Base Unit – (meter, gram, liter, second)
deci – d
0.1
centi – c
0.01
milli – m
0.001
micro - µ
0.000 001
nano – n
0.000 000 001
= 1*10 9
= 1*10 6
= 1*10 3
= 1*10 2
= 1*10 1
= 1*10 0
= 1*10 -1
= 1*10 -2
= 1*10 -3
= 1*10 -6
= 1*10 -9
Metric System
Understanding prefixes
Prefixes are short names and letter symbols for
numbers (powers of ten). A prefix is attached to
the front of a unit, without a space. Prefixes are
easier to write and say than powers of ten,
ordinary notation, or traditional number names.
Compare:
25 MW(pronounced and spelled out: 25 megawatts)
25 X106 (the 106 is a power of ten)
25 000 000 W (ordinary notation)
25 million watts (traditional number name)
Metric System
As you go up the "ladder" of these prefixes, the unit is
multiplied in steps of 1000, or 103.
km = 1000 X m
Mm = 1000 X km
Gm = 1000 X Mm
[kilometer]
[megameter]
[gigameter]
Going down the prefix scale, a unit is divided in steps of
1000. In other words, it is multiplied in steps of 0.001 (=
1/1000).
mm = 0.001 X m
µm = 0.001 X mm
nm = 0.001 X µm
[millimeter]
[micrometer]
[nanometer]
Metric System
Changing prefixes by moving the decimal point
Choose a prefix that will simplify an expression by eliminating
unnecessary placeholding zeros (non-significant digits). To switch to
the next larger prefix, move the decimal point three places to the left.
– 4 000 m = 4 km
– 1 500 mg = 1.5 g
– 500 mL = 0.5 L
– 76 000 kg = 76 Mg
– 2 300 µs = 2.3 ms
To switch to the next smaller prefix, move the decimal point three
places to the right.
– 0.005 m = 5 mm
– 0.009 kg = 9 g
– 0.003 2 mm = 3.2 µm
When moving the decimal point to the right, you may have to add one
or two place holding zeros at the end of the number to show where the
(unexpressed) decimal point goes.
– 0.03 g = 30 mg
– 0.2 L = 200 mL
Practice Problems
1) 120 mm = _______________cm
2) 48.6 g = _______________ cg
3) 84,000 cm = _______________ Mm
4) 19.7 mm = _______________m
5) 23.89 km = _______________cm
6) .098 mg = _______________kg
7) 29.9 Ms = _______________µs
Practice Problems
1. 421 m = _______________cm
2. 486 cg = _______________ Mg
3. 17,000 km = _______________ Mm
4. 17 mm = _______________dam
5. 23 km = _______________cm
6. 225,081 mg = _______________kg
7. 53 Ms = _______________µs
English – Metric Conversion
Tables
Linear Measure
Imperial
Metric
1 inch [in]
2.54 cm
1 foot [ft]
12 in
0.3048 m
1 yard [yd]
3 ft
0.9144 m
1 mile
1760 yd
1.6093 km
1 nautical mile
2025.4 yd
1.852 km
Linear Measure Practice
• Inches to Centimeters and cm to in
34.3 in = ??? cm
94 cm = ??? in
• Feet to Meters and m to ft
8 ft = ??? m
323 m = ??? ft
• Yards to Meters and m to yd
100 yd = ??? m
7.24 m = ??? yd
• Miles to Kilometers and km to mi.
51.8 mi = ??? km
5 km = ??? mi
Volume Measure
Imperial
Metric
1 in3 Cubic Inches
16.387 cm3
1 ft3 Cubic Feet
1,728 in3
1 fl oz Fluid Ounces
0.0283 m3
23.625 ml
1 pt Pint
20 fl oz
0.4725 l
1 gal
8 pt
3.780 l
Volume Practice
• Cubic inches to cubic centimeters
15 in3 = ??? cm3
31.7 cm3 = ??? in3
• Cubic feet to cubic meters
3 ft3 = ??? m3
894 m3 = ??? ft3
• Ounces to milliliters
89 oz = ??? ml
89 ml = ??? oz
• Gallons to liters
4 gal = ??? L
63 L = ??? gal
Mass Measure
Imperial
Metric
1 ounce [oz]
437.5 grain 28.35 g
1 pound [lb]
16 oz
0.4536 kg
1 stone
14 lb
6.3503 kg
1 hundredweight [cwt] 112 lb
50.802 kg
1 long ton (UK)
20 cwt
1.016 t
1 short ton (US)
2,000 lb
0.907 t
Physical Properties
Mass, Volume, and Density
Mass
What do you know about mass?
Mass
• Measure of the amount of matter that
makes up an object.
• Units used to designate mass are
kilograms (kg)
• You can measure an objects mass using a
balance (triple beam, electronic, spring).
Volume
What is Volume?
Volume
• Volume is a measurement of the threedimensional space occupied by an object.
• Units include cm3 and mL.
• Solids, liquids, and gases all have volume,
but you measure each differently.
– Solid – calculate geometrically or displacement
– Liquid – measure using a graduated cylinder
Density
How does Density relate to Mass
and Volume?
Density
• The amount of matter in a given space.
– Does this sound familiar?
• Concentration or Compactness
• The unit for density is
or
.
Mass, Volume, and Density
•
Mass volume and density are directly related.
Practice Exercise:
1. Measure the mass and volume of an object in the
room.
2. Calculate the Density of the Object.
3. What are the units associated with this
calculation?
Formulae
Density = Mass / Volume
Mass = Density x Volume
Volume = Mass / Density
Practice Problems
1. Calculate the volume of an object that is 34
cm by 25 cm by 8 cm.
2. Given:
V = 50 mL
Calculate: Mass
D = .75 g/mL
3. Given:
M = 55 g
Calculate: Volume
D = 2.3 g/cm3
4. Given:
M = .13 kg
Calculate: Density
V = 20 mL
Significant Figures
• It is important to record the precision of your
measurements so that other people can
understand and interpret your results.
• A common convention used in science to
indicate precision is known as significant
figures.
• Significant figures are those digits in a
measurement that are known with certainty plus
the first digit that is uncertain.
Significant Figures
Even though this ruler is
marked in only centimeters
and half-centimeters, if you
estimate, you can use it to
report measurements to a
precision of a millimeter.
Rules for Sig Fig
Rule 1
Zeros between other nonzero digits are significant.
Examples
a. 50.3 m has three significant figures
b. 3.0025 s has five significant figures
Rules for Sig Fig
Rule 2
Zeros in front of nonzero digits are not significant.
Examples
a. 0.892 has three significant figures
b. 0.0008 s has one significant figure
Rules for Sig Fig
Rule 3
Zeros that are at the end of a number and also to
the right of a decimal point are significant.
Examples
a. 57.00 g has four significant figures
b. 2.000 000 kg has seven significant figure
Rules for Sig Fig
Rule 4
Zeros that are at the end of a number but left of the
decimal point are not significant.
Examples
a. 100 m has ONE significant figure
b. 20 m has ONE significant figure
Rules for Sig. Fig.
Extra Rule
Zeros that are at the end of a number but left of the
decimal point that are measured to be significant
are indeed significant.
Examples
a. A scale measures 1200. kg has four significant
figures and is written in scientific notation:
3
1.200 x 10 kg
so Rule 3 applies