Chapter 2Analyzing Data International System of Units (S.I.)◦ Le Systeme International d`Unites.◦ Table 1 page 33 SI base units
Mass vs. Weight◦ Mass – kilogram (kg), measures the amount of
matter.◦ Weight – is the force of gravity on a sample of
matter.
Derived Units
Combination of two or more SI base units.◦ Volume = amount of space occupied by an object. length x width x height = (m3) Liquid Volume – (mL)
◦ Density = ratio of mass to volume.◦ D = m/v
Metric System
The International System of Units Standard
Based upon tens or decimal places. Used throughout the world.
Table of PrefixesPrefix Abbrev. MeaningTera- T 1012
Giga- G 109
Mega- M 106
kilo- k 103
hecto- h 102
deca- da 101
Base Units - meter, liter, gram, or second deci- d 10-1
centi- c 10-2
milli- m 10-3
micro- µ 10-6
nano- n 10-9
pico- p 10-12
Conversion Factors
Ratio derived from the equality between two different units, that can be used to convert from one to the other.◦ 1 dollar = 4 quarters
dollar 1quarters 4or
quarters 41dollar
2.2 Dimensional Analysis
Mathematical technique to help solve problems using conversion factors.
How many dollars do you have if you have 45 quarters in your bag?
Scientific Notation
Scientific Notation or Exponential Notation◦ Written as the product of two numbers. Coefficient and a power of 10.
◦ n. x 10e
◦ Where n is a digit 1-9. e is the exponent.
Proportions
Directly Proportional◦ Dividing one quantity by the other gives a
constant value.
Inversely Proportional◦ Product of two quantities are constant values.
Metric Conversions
Convert 50 kg to g.
Convert 30 cm to m.
Metric Conversions
Identify the conversion factors needed to convert cm to mm.
Identify the conversion factors needed to convert cm3 to mm3.
Conversion of Cubic Units of Volume
Practice◦ 1) 1.2 x 10-3 nm3 = ? mL
◦ 2) 1.4 x 10-2 m3 = ? mm3
Exit Problem
Before you leave you must complete the following conversion and place it in the folder on the teacher desk.
2.25 x10 -5 km3 = ? µm3
2.3 Uncertainty in Data
Accuracy◦ How close a single measurement comes to the
actual dimension or true value.
Precision◦ How close several measurements are to the
same value.
Percentage Error
accepted
acceptedexperiment
ValueValue Value
error %−
=
Error in MeasurementMeasurements always contain some
degree of error. +/- .5 error
Significant Figures
In a measurement include all the digits that are known precisely plus one last digit that is estimated.
Rules for Significant Figures
Significant Figures Rules for significant digits:◦ All non-zero digits are significant. 1234 5663 121112
◦ Zeroes in between two non-zero digits are always significant. 103 1004 102003
◦ Zeroes after a non-zero digits are only significant if the number has a decimal. 200. 3450. 10.
◦ Zeroes after non-zero digits are not significant if the number has no decimal. 200 40020 4230
◦ Zeroes in front of non-zero digits are never significant. .00004 0.0343 .00430
Sig Figs in Calculations
An answer can’t be more precise than the least precise measurement from which it was calculated.
Multiplication & Division◦ Round all answers to the fewest sig fig.
Addition & Subtraction◦ Round to the same number of decimal places as
the measurement with the least precision.
Sample Problems
1) (5.232x106 mm )(4.33x102mm)=
2)
3) 4.33x102cm + 1.2x102cm=
4) 7.90 kg – 4.2 kg=
=L 8.2x10g5.44x10
4
7
Word Problems
Using Dimensional Analysis◦ Round all answers to the number of significant
figures as the given.
p.p#1
If 1500 white blood cells (WBC) are lined up side by side they would form a row 1.0 in long. What is the average diameter in micrometers of a single WBC? (1in = 2.54cm)
p.p. #2
A radio wave travels 186000 miles per second. How many kilometers will the wave travel in one microsecond?(1 mi = 1.61 km)
p.p. #3 Eggs are shipped from a poultry farm in trucks.
The eggs are packed in cartons of one dozen eggs each; the cartons are placed in crates that hold 20 cartons each. The crates are stacked in the trucks, 5 crates across, 25 crates deep, and 25 crates high. How many eggs are in 5 truckloads?
1carton = 12eggs 1truck = 3125 crates1 crate = 20 cartons
p.p. #4
Iodine is an essential nutrient in our diet that prevents goiter. To obtain enough iodine, we can use iodized salt, which is .01%NaI by mass. How many kilograms of NaI should be added to 1000kg of table salt to achieve this percentage of NaI?
p.p. #5
The antlers of a deer are 50% Ca by mass. The calcium comes from leaves that the deer eat. The leaves are .07%Ca by mass. How many kilograms of leaves would a deer need to eat in order to provide enough calcium to grow antlers weighing 3 kilograms?