Chapter One:

CHEMICALFOUNDATIONS

Contents

Atoms vs. Molecules

p031-1 Chemistry: An Overview

Oxygen and Hydrogen Molecules

p03

A Chemical Reaction

A Chemical Reaction

p04

Science: A Process for UnderstandingNature and Changes

p05

1. Making observations (collecting data)

2. Making a prediction (formulating a hypothesis)

3. Doing experiments to test the prediction (testingthe hypothesis)

1-2 The Scientific Methodp05

Steps in the Scientific Method

Making observations. Observations may be qualitative

(the sky is blue; water is a liquid) or quantitative

(water boils at 100℃; a certain book weighs 2

kilograms). A qualitative observation does not involve

a number. A quantitative observation called a

measurement ) involves both a number and a unit.

Formulating hypotheses. A hypothesis is a possible

explanation for an observation.

Performing experiments. An experiment is carried

out to test a hypothesis. This involves gathering

new information that enables a scientist to decide

whether the hypothesis is valid.

that is, whether it is supported by the new

observation learned from the experiment.

Experiments always produce new observations, and

this brings the process back to the beginning again.

The Various Parts of theScientific Method

P05

Figure 1.5

Law vs. Theory

A law summarizes what happens.

A theory (model) is an attempt to explain

why it happens.

1-3 Units of Measurementp09

1 liter = (1 dm)3 = (10 cm)3 = 1000 cm3

cdcandelaLuminous intensitymolmoleAmount of substanceAampereElectric currentKkelvinTemperaturessecondTimemmeterLengthkgkilogramMass

AbbreviationName of UnitPhysical Quantity

cdcandelaLuminous intensitymolmoleAmount of substanceAampereElectric currentKkelvinTemperaturessecondTimemmeterLengthkgkilogramMass

AbbreviationName of UnitPhysical Quantity

Table 1.1 The Fundamental SI Units

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Nature of Measurement

Measurement - quantitative observation

consisting of 2 parts

Part 1 –number

Part 2 –scale (unit)

Examples:

20 grams

6.636.63 ×× 1010--3434 Joule seconds

Measure-ment ofVolumeUsing aBuret

p10

1-4 Uncertainty in Measurementp10

Uncertainty in Measurement

A digit that must be estimated is called

uncertain.

A measurement always has some degree of

uncertainty.

Ex 1.1 Uncertainty in Measurement

In analyzing a sample of polluted water, a chemistmeasured out a 25.00-mL water sample with a pipet. Aanother point in the analysis, the chemist used agraduated cylinder to measure 25 mL of a solution.What is the difference between the measurements25.00 mL and 25 mL?

Solution:

The quantity 25 mL means that the volume is between 24mL and 26 mL, whereas the quantity 25.00 mL meansthat the volume is between 24.99 mL and 25.01 mL. Thepipet measures volume with greater precision than doesthe graduated cylinder.

p11

The Difference Between Precision and Accuracy p12

Ex 1.2 Precision and Accuracy

To check the accuracy of a graduated cylinder, a studentfilled the cylinder to the 25-mL mark using waterdelivered from a buret and then read the volume delivered.Following are the results of fives trials. Is the graduatedcylinder accurate?

Solution:

The student has good technique. However, note that theaverage value measured using the buret is significantlydifferent 25 mL. It produces a systematic error.

p13

Rules for CountingSignificant Figures - Details

Nonzero integers always count as

significant figures.

3456 has 4 sig figs.

1-5 Significant Figures andCalculations

p13

Rules for Counting SignificantFigures –Details (continued)

Leading zeros do not count as significant

figures.

0.048 has 2 sig figs.

Rules for Counting SignificantFigures –Details (continued)

Captive zeros always count as significant

figures.

16.07 has 4 sig figs.

Rules for Counting SignificantFigures –Details (continued)

Trailing zeros are significant only if the

number contains a decimal point.

9.300 has 4 sig figs

150 has 2 sig figs.

Rules for Counting SignificantFigures –Details (continued)

Exact numbers have an infinite number

of significant figures.

1 inch = 2.54 cm, exactly

Ex 1.3 Significant Figures p14

Give the number of significant figures for each of thefollowing results.

a. A Student’s extraction procedure on tea yields 0.0105g of caffeine.

b. A chemist records a mass of 0.050080 g in an analysis.

c. In an experiment a span of time is determined to be8.050 x 10-3 s.

Solution:a. The number contains three significant figures.

b. The number contains five significant figures.

c. This number has four significant figures.

Ex 1.4 Significant Figures inMathematical Operations

p15

Carry out the following mathematical operations, andgive each result with correct number of significantfigures.

a.1.05 x 10-3 ÷ 6.135

b. 21-13.8

c. The following values ere obtained : P =2.560, T =275.15, and V = 8.8. Using R = (PV)/T todetermine the value of gas constant (R).

Solution:

1-6 Dimensional Analysis p16

Converting from One Unit to Another

p17

To convert from one unit to another, use the

equivalence statement that relates the two units.

Derive the appropriate unit factor by looking at the

direction of the required change (to cancel the

unwanted units).

Multiply the quantity to be converted by the unit

factor to give the quantity with the desired units.

Ex 1.5 Unit Conversions I

A pencil is 7.00 in long. What is its length in

centimeters?

p17

Solution:

In this case we want to convert from inches to

centimeters. Therefore, we must use the reciprocal of

the unit factor used above to do the opposite conversion:

cm17.8cm4)(7.00)(2.5in1cm2.54

in7.00

Ex 1.6 Unit Conversions II

p18

You want to order a bicycle with a 25.5-in frame. But

the catalog are given only in centimeters. What size

should you order?Solution:

Ex 1.8 Unit Conversion IVP19

The speed limit on many highways is 55 mi/h. What

number would be posted in kilometers per hour?Solution:

1.7 Temperature p20

Figure 1.11 The three major temperature scales.

Ex 1.13 Temperature Conversions p21

Normal body temperature is 98.60F. Convert this

temperature to the Celsius and Kelvin scales.

Solution:

C37.0F9C5

F66.6 00

00

a. The number of Fahrenheit degrees between

32.00F and 98.60F is 66.60F. We must convert

this difference to Celsius degrees.

b. Tk = Tc +273.15 = 37.0 + 273.15 = 310.2 K

1-8 Density p24

Ex 1.13 Determining Density

A chemist , trying to identify the main component of acomponent of a compact disc cleaning fluid, finds that25.00 cm3 of the substance has a mass of 19.625 g at 20℃.The following are the names and densities of thecompounds that might be the main component? Which ofthese compounds is the most likely to be the maincomponent of the compact disc cleaner?

Solution

This density corresponds exactly to that of isopropyl alcohol.

p24

1-9 Classification of Matter p25

Figure 1.13 The three states of water.

Structure of a Solid

Structure of a Liquid

Structure of a Gas

Simple Laboratory Distillation Apparatus

Figure 1.14

p27

The Organization of Matterp28

The Organization of Matter

The Organization of Matter

The Organization of Matter p28

Homogeneous Mixtures

Mixture vs. Solution

Mixture vs. Compound