Chapter 1 Chemistry: An Introduction

Unit 1: Chemistry An IntroductionChapter 1Chemistry: An Introduction

Chapter 2Measurements and Calculations

Why is chemistry important?used to produce NEW PRODUCTS

develop ENERGY sources

helps to fight and control DISEASESWho needs to know chemistry?Doctors and nursesEnvironmentalistsCosmetologistsJanitors Why is chemistry important to me? helps you make informed decisions

you will become a better problem solverCHEMISTRY IS NOT EASYBUT ITS NEVER IMPOSSIBLE!!

You will be successful if youASK QUESTIONS & GET HELP DONT CHEATHAVE GOOD ATTENDANCEBE ACTIVE IN YOUR EDUCATION

Chemistry isWhat is the definition of chemistry?The study of matter and all the changes it can go throughchemistry is the CENTRAL science!Steps of the Scientific Method1. Make OBSERVATIONS about the problem or situation you are studying.

*can be QUANTITATIVE - measurement involving a number

*can be QUALITATIVE - noting the quality of somethingScientific Method continued2. Formulate a HYPOTHESIS by proposing possible solutions or explanations for your observations.Scientific Method continued3. Test hypothesis with an EXPERIMENT.Variable: A FACTOR THAT CONTROLS THE OUTCOME OF THE EXPERIMENTIndependent variable: FACTOR THAT YOU CONTROL**always graphed on the x-axisScientific Method continuedDependent variable: FACTOR THAT RESPONDS TO CHANGES IN THE INDEPENDENT VARIABLE**always graphed on the y-axisControlled experiment: PROCEDURE THAT TESTS ONLY ONE FACTOR AT A TIME

Scientific Method continued4. Assemble tested hypotheses into a THEORY or model.*gives overall explanation as to WHY nature behaves a certain way*can be proven FALSE if contradictory evidence becomes availableScientific Method continued5. Explanations for observed behaviors are known as LAWS.

*tells you HOW nature will act

*Law of gravity*Newtons Laws of physicsChapter 2

Measurements and CalculationsWhat are measurements?QUANTITATIVE (numeric) observations and are very important to scienceSection 2.1 Scientific Notationscientific notation is used to make very BIG or very SMALL numbers more compact and easier to write

PROPER scientific notation means# between 1 and 10 x 10Awhere A is the number of times the decimal point was moved**keep only one digit to the left of the decimal pointStandard notation scientific notation

moving the decimal point LEFT = POSITIVE exponent545,000 = ____________________moving the decimal point RIGHT = NEGATIVE exponent0.000167 = ____________________remember LIP = left is positive!Standard notation scientific notation

moving the decimal point LEFT = POSITIVE exponent545,000 = 5.45 x 105moving the decimal point RIGHT = NEGATIVE exponent0.000167 = 1.67 x 10-4remember LIP = left is positive!Scientific notation standard notation*POSITIVE EXPONENT = big number

*NEGATIVE EXPONENT = small number

2.38 x 107 = ___________________

4.3 x 10-2 = _______________Scientific notation standard notation*POSITIVE EXPONENT = big number

*NEGATIVE EXPONENT = small number

2.38 x 107 = 23800000

4.3 x 10-2 = 0.043Section 2.2 Units

all measurement must have a UNITlets you know what SCALE is being used

English systemMetric system (used in science and most of the world)

SI Unitsbased off the metric system and were decided as the fundamental units for certain quantitiesQuantitySI Base UnitUnit SymbolLength, lMetermMass, mKilogramkgTemperature, TKelvinKTime, tSecondsAmount of substance, nMolemolMetric PrefixesSI units can be inconvenient in size, so we use METRIC prefixes to change the size of the unit.

Prefix/AbbreviationRelationship to Base Unit (g)Mega-1 Mg = 106 gkilo-1 kg = 103 gdeci-1 dg = 0.1 g or 10 dg = 1 gcenti-1 cg = 0.01 g or 100 cg = 1 gmilli-1 mg = 0.001 g or 1000 mg = 1gmicro-1 g = 0.000 001 g or 106 g = 1g nano-1 ng = 0.000 000 001 g or 109 ng = 1gSection 2.3 Measurements of Length, Volume and MassLength SI unit metercan use prefixes to make bigger or smaller

(1 m = 39.37 in.) or (1 in. = 2.54 cm)

*measured with a RULER or METER STICKVolumeAmount of 3-dimensional space take up by an objectSI Unit cubic meter, m3called a DERIVED unit because it is a combination of unitsnot convenient to use the SI unit when measuring volume of liquids*measured with a RULER or a GRADUATED CYLINDER

Volumewhen measuring liquid volume, you must read the bottom of the curve of the liquid, called the MENISCUS

common units liter or milliliter

Massquantity of matter present in an objectSI unit kilogramwe will use grams, because the kilogram is too bigMeasured with a BALANCE

MASS and WEIGHT are not the same! Weight is a FORCE produced by the product of your mass and gravity. We use the term weight incorrectly!

Section 2.4 Uncertainty in Measurementa measurement requires ESTIMATION

everyone estimates differently, which leads to UNCERTAINTYSection 2.4 Uncertainty in Measurementwhat would you say is the length of this cube?

we know it is definitely between the 3.1 cm and 3.2 cm, but the number in the hundredths place is estimated called an UNCERTAIN number.

Significant Figures (sig figs):In a measurement, all the known digits plus one estimated digitgood measurements need to be ACCURATE and PRECISE

Accuracy and PrecisionACCURACY: closeness of a measurement to its true value*can be evaluated using percent error

Accuracy and PrecisionPRECISION: the exactness of a measurement

determined by the # of decimal places and repeatability of the measurementSection 2.5 Significant Figureschemistry requires calculations of different measurements

important to know the degree of uncertainty of your final result

Rules determine how many digits we have in our answers

Counting Sig Figs The Rules

1. All nonzero numbers are significant.5742 cm has ______ sig figsCounting Sig Figs The Rules 2. Leading zeros preceding all nonzero numbers are NOT significant.

0.005742 kg has ______ sig figsCounting Sig Figs The Rules 3. Captive zeros are found between nonzero numbers and are significant.

0.00570042 mi has ________ sig figsCounting Sig Figs The Rules 4. Trailing zeros are found at the right end of the nonzero digits and are only significant if the number is written with a decimal point.1200 cm has _____ sig figs1200. cm has ______ sig figsCounting Sig Figs The Rules 5. Exact numbers are determined by counting or are a part of a definition and have an unlimited number of sig figs.1 mi = 5280 feet25 students*these kinds of numbers are not used to determine how many sig figs are in your final answer

Counting Sig Figs The Rules 6. These rules also count for number written in scientific notation.6.0 x 10-5 km has _______ sig figsRounding Numbers1. If the digit to be removed isa. < 5, the preceding digit REMAINS THE SAME1.33 rounded to 2 sig figs is _________b. 5, the preceding digit is ROUNDED UP1.36 rounded to 2 sig figs is _________Rounding Numbers2. When doing several calculations, carry the extra digits through all of the calculations then round the FINAL ANSWER.*when rounding, only look to the first number to right of the digit to be rounded4.348 rounded to 2 sig figs is 4.3, NOT 4.4!Determining Sig Figs in Calculations 1. Multiplication and Division the number of sig figs in the final answer is the same as the measurement with the LEAST number of sig figs. You have to count the sig figs is the measurement(s).4.56 x 1.4 = 6.384 6.4 (3 sig figs) (2 sig figs) (2 sig figs in answer)5.18 X 0.0208 = __________________Determining Sig Figs in Calculations2. Addition and Subtraction the answer is limited by the measurement with the LEAST number of decimal places.12.1118.0 + 1.01331.123 31.1Determining Sig Figs in Calculations 3. For combined operations, round in between operations so that you can keep track of the correct number of sig figs.Section 2.6 Problem Solving and Dimensional AnalysisDimensional analysis method of CONVERTING UNITSEquivalence statement relationship between two different UNITS that equal the same quantityConversion factor a ratio of the two parts of the EQUIVALENCE statement that relates the two units

Dimensional Analysisevery equivalency gives 2 conversion factors

choose the factor that has the WANTED unit on top of the GIVEN unit you are trying to cancel outDimensional AnalysisPROBLEM: Convert 2.85 cm to inchesStep 1. Choose the equivalence statement that relates the two units.Step 2. Choose the appropriate conversion factor (wanted units over given).Dimensional AnalysisStep 3. Multiply the given quantity by the conversion factor.

Step 4. Check that you have the correct number of sig figs in your answer.

Step 5. Does your answer make sense?

Dimensional AnalysisYou will have to do multi-step conversions. These will require more than one conversion factor.Do all of the math at one time and round the final answer!Dimensional AnalysisPROBLEM: Racing cars at the Indianapolis Motor Speedway now routinely travel around the track at an average speed of 225 mi/h. What is this speed in kilometers per minute?Section 2.7 Temperature ConversionsThree different temperature scales:

1. Fahrenheit - scale mostly used in the US and Great Britain (unit F)2. Celsius - used in most other countries, based off the freezing point and boiling point of water (units C)3. Kelvin - used in the sciences, absolute scale, NEVER A NEGATIVE VALUE (unit K, not degrees!)Temperature Conversionsthe size of one degree on the CELSIUS scale is the same as one unit on the KELVIN scale

one degree FAHRENHEIT is smaller than one unit on the other two scalesConverting Between the Kelvin and Celsius ScalesEQUATION:TK = TC + 273

PROBLEM: What is 70C on the Kelvin scale?

PROBLEM: Liquid nitrogen boils at 77 K. What is the boiling point on the Celsius scale?Converting Between the Fahrenheit and Celsius ScalesEQUATION: TF = 1.8TC + 32PROBLEM: What is 28C expressed in Fahrenheit?Temperature ConversionsPROBLEM: An antifreeze solution in a cars radiator boils at 239 F. What is this temperature on the Celsius scale?

if converting K F, you must first convert to Celsius!

Section 2.8 DensityDensity is amount of mass per unit of volume

EQUATION:

*remember that 1 mL = 1 cm3

DensityWATER DISPLACEMENT is used to measure the volume of an irregular solid

density can be used to IDENTIFY a pure substance (element or compound), because it does not change

DensityPROBLEM: A medallion has a mass of 55.64 grams. A graduated cylinder is filled to a volume of 75.2 mL and when the medallion is placed in the cylinder, the water volume rises to 77.8 mL. What is the density and is this medallion platinum (d = 21.4 g/cm3) or silver (d = 10.5 g/cm3)?

Using Density in CalculationsPROBLEM: The density of the element mercury is 13.6 g/mL. What volume of mercury must be taken to obtain 225 g of the metal?Using Density in CalculationsPROBLEM: Magnesium has a density of 1.74 g/cm3. What mass of magnesium would have a volume of 15.0 cm3?Density Graphing

density is determined by measuring the MASS & VOLUME of an object

when graphing density, the VOLUME goes on the x-axis and the MASS goes on the y-axisDensity Graphingdensity is found by determining the SLOPE of the line created by the data

EQUATION:

Density GraphingProblem: What is the density of the object represented by the graph?

GraphingWhat is the independent variable? The variable YOU controlWhere does is go on the graph? x-axisWhat is the dependent variable? The variable that responds to the independent variableWhere does it go on the graph?y-axisGraphingWhat is the difference between a line graph and a scatter plot?

What is a best-fit line? A straight line that represents the average of the data points.

The End