Chapter 2: Measurement and Problem Solving

CHAPTER 2: MEASUREMENT AND PROBLEM SOLVING

16 days

First day of school Lab safety

Day One

Syllabus HIGHLIGHTS!!!

Expectations Be Prepared NO FOOD OR DRINK IN THIS

CLASSROOM EVER!!! How do I get a good grade? Hall Passes Absences

MISCELLANEOUS BOOKS: Put name in front cover and please

cover the book!

Three ring binder

Calculator

Email

Lab Safety Contract

Lab Notebook

Labs Spiral bound notebookLab procedure: found online and in the room Must be written in your lab notebook before you

begin lab as well as any data tables you may need

Completed with a partner but must be a collaborative effort

Each partner is responsible to have the data before they leave the room

Lab Safety Video

Location of Safety Equipment Goggles Aprons Sand Eyewash station Safety Shower MSDS Sheets

Fire Blanket Fire extinguisher Emergency Stop

Button Fire Alarm Fume hood Broken Glass

Container Assignment: Draw a diagram of the room and label the safety equipment listed above.

Explain what each of the above is used for and when they are used.

WebsitesMeasurements & Scientific

Notation

Day Two

Two websites you will be using all year!!! www.nordoniahonorschemistry.wikispac

es.com Class website Lab manual Calendar Lecture Notes Answer Keys to Homework

www.masteringchemistry.comAdditional Reviews and assignments

What Is a Measurement?

Quantitative observation

Comparison to an agreed upon standard

Every measurement has a number and a unit

A Measurement

The unit tells you to what standard you are comparing your object.

The number tells you:1.What multiple of the standard the object

measures.

2. The uncertainty in the measurement.

Scientists have measured the average global temperature rise over the past century to be 0.6 °C

°C tells you that the temperature is being compared to the Celsius temperature scale.

0.6 tells you that:1. The average temperature rise is 0.6

times the standard unit of 1 degree Celsius.

2. The confidence in the measurement is such that we are certain the measurement is between 0.5 and 0.7 °C.

Scientific Notation

We should all be familiar with this but I just want to remind you of a few things!!!

S.N. is an easy way to express VERY large or VERY small numbers

Chemistry most of the time deals with extremely small number considering we talk about atoms!

3 parts to S.N.

1.2 X 10-9

How to Express a number in Scientific Notation

1. Move the decimal point to obtain a number between 1 and 10.

2. Write the result from Step 1 multiplied by 10 raised to the number of places you moved the decimal

** The exponent is POSITIVE if you moved the decimal to the LEFT

** The exponent if NEGATIVE if you moved the decimal to the RIGHT

Practice—Write the Following in Scientific Notation

123.4

145000

25.25

1.45

8.0012

0.00234

0.0123

0.000 008706

Practice—Write the Following in Standard Form2.1 x 103

9.66 x 10-4

6.04 x 10-2

4.02 x 100

3.3 x 101

1.2 x 100

Metric and Factor Label

Day Three

Metric System

Group of units used to make any kind of measurements

Best known for its simpleness Why is it so simple?

Used all around the world with scientists

The Standard Units Scientists generally report results in an

agreed upon International System. The SI System

Aka Système International

Quantity Unit SymbolLength meter mMass kilogram kgTime second sTemperature kelvin K

Some Standard Units in the Metric System

Quantity Measured

Name of Unit Abbreviation

Mass gram g

Length meter m

Volume liter L

Time seconds s

Temperature Kelvin K

King Henry Died By Drinking Chocolate Milk

K H D B d c m

Tro's "Introductory Chemistry", Chapter 2 23

Common Prefixes in the SI System

Prefix SymbolDecimal

EquivalentPower of 10

mega- M 1,000,000 Base x 106

kilo- k 1,000 Base x 103

deci- d 0.1 Base x 10-1

centi- c 0.01 Base x 10-2

milli- m 0.001 Base x 10-3

micro- m or mc 0.000 001 Base x 10-6

nano- n 0.000 000 001 Base x 10-9

Let’s Try A Few

125 cm = ____________ mm

0.2568 L = _________ mL

2.56 kg = ________ g

Factor LabelDimensional Analysis EASY way to convert from one unit to

another unit!!

WE will be doing this ALL YEAR long! So you better pay attention now!

UNITS ARE EXTREMELY IMPORTANT

Units Always write every number with its

associated unit. Always include units in your calculations.

You can do the same kind of operations on units as you can with numbers.○ cm × cm = cm2

○ cm + cm = cm○ cm ÷ cm = 1

Using units as a guide to problem solving is called dimensional analysis.

Problem Solving and Dimensional Analysis

Many problems in chemistry involve using relationships to convert one unit of measurement to another.

Conversion factors are relationships between two units.May be exact or measured.

Conversion factors generated from equivalence statements.e.g., 1 inch = 2.54 cm can give or in1

cm54.2cm54.2

in1

Problem Solving and Dimensional Analysis, Continued

Arrange conversion factors so the starting unit cancels.Arrange conversion factor so the starting unit is on

the bottom of the conversion factor. May string conversion factors.

So we do not need to know every relationship, as long as we can find something else the starting and desired units are related to :

unit desired unit related

unit desired

unitstart

unit relatedunitstart

unit desired unitstart

unit desiredunitstart

Systematic Approach

1. Write down the given amount and unit.

2. Write down what you want to find and unit.

3. Write down needed conversion factors or equations.

Common Units and Their EquivalentsLength

1 kilometer (km) = 0.6214 mile (mi)1 meter (m) = 39.37 inches (in.)1 meter (m) = 1.094 yards (yd)

1 foot (ft) = 30.48 centimeters (cm)1 inch (in.) = 2.54 centimeters (cm) exactly

Common Units and Their Equivalents, Continued

Volume1 liter (L) = 1000 milliliters (mL)1 liter (L) = 1000 cubic centimeters (cm3)1 liter (L) = 1.057 quarts (qt)

1 U.S. gallon (gal) = 3.785 liters (L)

Mass1 kilogram (km) = 2.205 pounds (lb)

1 pound (lb) = 453.59 grams (g)1 ounce (oz) = 28.35 (g)

Lets take a look at one!

I drive 20 miles to school every day. I want to know how many kilometers I drive.

Lets Try a Few

125 lb = ________ kg

2.5 gallons = ________ L

3.1 km = _________ miles

Significant Figures and Factor label

Day Four

Exact Numbers vs. Measurements

Sometimes you can determine an exact value for a quality of an object.Often by counting.

○ Pennies in a pile.

Sometimes by definition○ 1 ounce is exactly 1/16th of 1 pound.

Whenever you use an instrument to compare a quality of an object to a standard, there is uncertainty in the comparison.

Reporting Measurements Measurements are written to indicate the

uncertainty in the measurement. The system of writing measurements we

use is called significant figures. When writing measurements, all the digits

written are known with certainty except the last one, which is an estimate.

45.872

CertainEstimated

45.872

Skillbuilder 2.3—Reporting the Right Number of Digits

A thermometer used to measure the temperature of a backyard hot tub is shown to the right. What is the temperature reading to the correct number of digits?

Reporting Numbers with Sig. Figs When we report numbers in this class

we need to make sure that we do not report them more specific than they really are. WHAT???

Volume of a box

Length = 7.12 cm

Width = 2.15 cm

Height = 2.15 cm

How do I know if a number is significant?

1. All NONZERO digits are significant

2. Zeros between two nonzero numbers are significant

3. Trailing zeros are significant

4. Leading zeros are NOT significant, they are only place holders

5. Zeros at the end of a number but before a decimal are NOT significant

Lets try a few

0.0035 1.080 2371 2.97 x 105

100000 0.500 58.31

Factor Label (Multi-step)

I went to the Yukon last summer and the speed limit sign said 105 km/hr. What was the speed limit in mi/hr?

If I drive a total of 50 miles a day and my car gets 49 miles/gallon. How much does it cost me a week to drive to work? Assuming price for gas is $2.50/gallon.

A circle has an area of 2,659 cm2. what is its area in square meters?

Significant Figures and Factor Label

Day Five

Significant Figures in CalculationsADDITION AND SUBTRACTION

The difference and sum carries the same number of decimal places as the quantity carrying the FEWEST decimal places.

3.449 cm – 0.76 cm =

2.5 cm + 2 cm =

Significant Figures in Calculations(MULTIPLICATION AND DIVISION)

The results carries the same number of significant figures as the factor with the FEWEST figures.

5.892 cm X 6.10 cm =

Lets take a look back at our Volume of a Box!!

Volume of a box

Length = 7.12 cm

Width = 2.15 cm

Height = 2.15 cm

Lets Try a Few!

1.01mm x 0.12 cm x 53.51 cm =

56.55 cm x 0.920 cm =

345.0 ml / 120 ml =

Significant Figures Lab

Day Six

Mastering Chemistry Website

Day Seven

Density Day Eight

Density

Ratio of its mass to volume

“How much stuff is in a given space”

Differs from one substance to another

How do I calculate DENSITY?

What about the units?

I have a sample of platinum that has a mass of 5.84g and it displaces 0.556 cm3 of water. What is the density?

Lets Try a Few!

The gasoline in an automobile gas tank has a mass of 60.0 kg and a density of 0.752g /cm3. What is its volume in ml?

A steel cylinder has a volume of 246 cm3 and a density of 7.93 g/cm3. What is its mass in kg?

Density Day 2 Day Nine

Measurement and Density Lab

(Sig. Figs. Lab)

Day Ten and Eleven

Practice TestDay Twelve

reviewDay Thirteen

Test

Day Fourteen