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?