ChemistryChemistry

Introduction

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• Definitions

• Classification of Matter

• Properties of Matter

• Measurement and SI Units

• Working with Numbers

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DefinitionsDefinitions• MatterMatter is anything that occupies space and

has mass.

• ChemistryChemistry is the study of matter and the changes it undergoes

• A substancesubstance is matter that has a definite or constant composition and distinct properties

Examples are water, silver, sugar, table salt, etc.

Matter

MixturesPure

Substances

HomogeneousMixtures

HeterogeneousMixtures Compounds Elements

Separation by Chemical Methods

Separation by Physical Methods

Properties of MatterProperties of Matter

Physical Property

Chemical Property

Extensive Property

Intensive Property

Physical PropertyPhysical PropertyA physical property can be measured and observed without changing the composition of a substance.

Examples:Examples:

Boiling Point

Density

Conductivity

Chemical PropertyChemical PropertyA chemical property refers to the ability of a substance to react with other substances. In order to observe this property a chemical change must take place.Examples:Examples:

Sugar ferments to form alcohol

Hydrogen burns in oxygen to create water.

Extensive PropertyExtensive PropertyMeasurable properties which depend on the amount of substance present are called extensive properties.

Examples:Examples:

Mass

Length

Volume

Intensive PropertyIntensive PropertyMeasurable or observable properties which are independent of the amount of substance present are called intensive properties.Examples:Examples:

Color

Density

Temperature

Measurement and SI UnitsMeasurement and SI UnitsSI units are an international standard of units developed in 1960 based on the decimal (base 10) system.

Base Quantity Name of Unit Symbol

Length meter m

Mass Kilogram kg

Time second s

Temperature kelvin K

Amount of Substance

mole mol

LengthLengthLength measures the extent of an object.

Length can be used to determine derived units such as area and volume.

Area = m x m = m2

Volume = m x m x m = m3

1 Liter (L) = 1dm3 (One cubic decimeter)

1 milliliter (mL) = 1cm3 (One cubic centimeter)

1 L = 1000 mL

Density d = m/V (mass per unit volume)

MassMassMass is a measure of the quantity of matter inside of a substance or object.

It should not be confused with the term weight, which is a measure of the force that gravity exerts on an object. They are related by the following equation;

F = mg

where g is the acceleration due to gravity, m is the mass and F is the force in Newtons

In chemistry, the smaller unit of mass grams (g) is preferable to kilograms (kg). 1kg = 1000g

TemperatureTemperature

Temperature measures the average kinetic energy of the particles contained within a system or object.

Although Kelvin are the accepted SI unit, the Celsius scale is often used. Both are based on the decimal system. The Fahrenheit scale is seldom used for scientific measurement.

Refer to the next frame for a comparison of temperature scales and conversion factors.

Temperature Comparisons and Temperature Comparisons and ConversionsConversions

Kelvin Celsius Fahrenheit

100 212373 Water Boils

98.6

25 77

37

0

298

310

32273

K oC oF

BodyTemperature

Water Freezes

RoomTemperature

oF = 9/5 oC + 32

oC = (oF - 32)5/9

K = oC + 273

Working With NumbersWorking With Numbers

Scientific Notation

Significant Figures

Accuracy and Precision

Factor-Label Method of Solving Problems

Scientific NotationScientific NotationAllows representation of large or small numbers accurately.

Removes possible ambiguity about significant figures.

Numbers are expressed follows;

N x 10n

where N is a number between 1 and 10 and n is an integer exponent that is positive if the decimal point is moved to the left to make N between 1 and 10, and negative if it must be moved to the right.

ExamplesExamples

1. The number 5,876.73 is expressed in scientific notation as;

5.87673 x 103

2. The number .000034785 is expressed as;

3.4785 x 10-5

Addition and SubtractionAddition and Subtraction

1. Write each number so that n has the same exponent

2. Add or subtract the N parts of the numbers

3. The exponent n remains the same

Example:

2.3x104 + 1.5x103 would be rewritten as 2.3x104 + .15x104 and the final answer would be 2.45 x 104.

Multiplication and DivisionMultiplication and Division

1. Multiply or divide the N parts of the numbers together

2. Add the exponents, n, if multiplying

3. Subtract exponents if dividing

Example:

3.0x103 x 4.0x104 = 12x107 = 1.2x108

Significant FiguresSignificant FiguresSignificant figures refer to the meaningful digits in a measured or calculated quantity

The last digit is understood to be uncertain when significant figures are counted

GuidelinesGuidelines• Any digit that is not zero is significant

•Zeros between nonzero digits are significant

•Zeros to the left of the first nonzero digit are not significant

•If a number is greater than 1, then all the zeros written to the right of the decimal point count as significant figures

•For numbers that do not contain decimal points, the trailing zeros (zeros after the last nonzero digit) may or may not be significant. This is one reason why it is important to use scientific notation

Calculations Involving Sig FigsCalculations Involving Sig FigsAddition and Subtraction: The number of digits to the right of the decimal point in the final answer is determined by the lowest number of significant figures to the right of the decimal in any of the original numbers

Multiplication and Division: The number of significant figures in the final answer is determined by the original number that has the smallest number of significant figures

Exact numbers (from definitions or by counting) are considered to have an infinite number of significant figures

For chain (multiple) calculations, carry the intermediate answers to one extra decimal place and round the final answer to the correct digits

Accuracy and PrecisionAccuracy and Precision

Accuracy tells how close a measurement is to the true value of the quantity that was measured

Precision refers to how closely two or more measurements of the same quantity agree with one another

Precise and accurate Precise but not accurate

Neither precise nor accurate

Dimensional AnalysisDimensional Analysis(Factor Label Method)(Factor Label Method)

Allows accurate conversion between units of similar types

It utilizes the fact that equivalent quantities using different units may be set up as a ratio to convert from one type of unit to another

Algebraically, labels are treated exactly the same way as the numbers they refer to

The unit you are converting to should always be placed in the ratio such that the old units cancel out and the new unit is in the desired position whether numerator or denominator

ExamplesExamples1in = 2.54cm therefore the ratio 1in/2.54cm or 2.54cm/1in may by used to convert centimeters to inches or inches to centimeters, respectively

100in x (2.54cm/1in) = 254cm

1km = 0.6215mi

10km x (0.6215mi/1km) = 6.215mi