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Chapter 1The Nature of Science
Standards of MeasurementAccurate measurement is needed in a
valid experiment.Standard—an exact quantity that
people agree to use for comparison.In order for a measurement to make
sense, it must include a number AND a unit.Examples: 150 ft, 35 cm, 64 mi
Measurement SystemsUS: English system (pounds, feet, inches,
Fahrenheit)Most other nations: metric systemScience Worldwide: an improved
version of the metric system called “International System of Units” or SI units. SI comes from the French Le Systeme
Internationale d’Unites It is easier to convert units and share with
others around the world.
The SI SystemSI Measurements and Base units
Base unit for length is the meter (m)Converted unit: centimeter, kilometer
Base unit for mass is the kilogram (kg)Converted unit: gram, milligram
Base unit for time is the second (s)Converted unit: microsecond
Base unit for electric current is the ampere (amp)
Base unit for temperature is the kelvin (K) Base unit for volume is the liter (L)
The SI SystemThe SI system is based on the number 10.Prefixes are used with the names of the units to indicate
multiples of 10.
Prefix multiplying factor kilo = 1000 (thousand) deci = 1/10 or 0.1 (tenth) centi = 1/100 or 0.01 (hundredth) milli = 1/1000 or 0.001 (thousandth) micro = 1/1,000,000 or .000 001 (millionth) nano = 1/1,000,000,000 or 0.000 000 001(billionth)Something Called SI
Derived UnitsDerived Unit: a unit that
combines different SI unitsCommon Derived Units:
Area: cm2 or m2
Volume: cm3 or m3
Density: g/mL or g/cm3
Transition
http://www.movoto.com/blog/opinions/south-dakota-unreal/
How can an aircraft carrier float?
What is density?
It is a derived unit.
Density= mass divided by volume.
How do you determine mass? Use a balance.
Measure in grams or kilograms.
Mr. Edmonds Rock to an Oldie
How do you determine volume?
We will express volume in cm3 and mL.
For a rectangular prism, V= L x W x H
For a liquid, measure volume using a graduated cylinder
.Find density first 90 seconds approximately no sig figs
Base units Meters Liters and Grams focus on liters
Density=mass volume
Because 1 cm3 = 1 mL
Density=m (grams) = m (g)
V (cm3) v (mL)Example:
D=62.4 g/ (8.5 cm x 2.5 cm x 3.3cm)=
D=62.4 g/ 70.1 cm3 = .9 g/ cm3
Accurate Measurement ReadingsRead to the nearest mark, then estimate
the number one decimal place further.
49.6 can be read with the lines on the rulerEstimate the last digit
49.66 cm
47.1 can be read with the lines on the ruler Estimate the last digit
47.10 cm
6.1 can be read with the linesEstimate the last digit
4.4 can be readEstimate the last digit
Dimensional AnalysisSometimes things need to be
converted to different units.You can use a conversion factor
(a ratio) to change one unit to another.Ex. 1 in = 2.54 cm
This process is called dimensional analysis
Conversion Process5 Steps of Dimensional Analysis
1. Start with the given (number & unit)
2. X (times)
3. Write the conversion factor as a fraction with the given unit on the bottom and new unit on top
4. Cross out units that cancel5. Calculate & write the correct answer &
units
Example: How many centimeters is 6.74 in?1. Start with the given (number & unit)
2. X (times)
3. Write the conversion factor as a fraction with the given unit on the bottom and new unit on top 1 in = 2.54 cm
4. Cross out units that cancel5. Calculate & write the correct answer &
units 6.74 in 2.54 cm1 in
= 17.12 cmX
Metric Conversions: The Ladder Method.
KILO1000
kHECTO
100h
DEKA10da
DECI0.1d
CENTI0.01
cMILLI0.001
m
MetersLitersGrams
seconds
Ladder Method
How do you use the “ladder” method?
1 – Determine your starting point.
2 – Count the “jumps” to your ending point.
3 – Move the decimal the same number of jumps in the same direction.
4 km = ________m
12
3
How many jumps does it take?
Starting Point
Ending Point
4. 1
_
_.2_
_.3_
_.= 4000 m