Chemistry Introduction. Menu Definitions Classification of Matter Properties of Matter Measurement...
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Transcript of Chemistry Introduction. Menu Definitions Classification of Matter Properties of Matter Measurement...
ChemistryChemistry
Introduction
MenuMenu
• Definitions
• Classification of Matter
• Properties of Matter
• Measurement and SI Units
• Working with Numbers
Quit
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