Introduction to chemistry

Introduction to chemistry:Scientific method, measurement, basic properties of matterMs. Buroker

1An Introduction to ChemistryWhy Chemistry?

The Scientific MethodThe Metric SystemMeasurement: Importance of NumbersLESSON TOPICSPrecision and Accuracy2What is Chemistry?A basic definition of chemistry would be, ________________________________________________________.Matter- _______________________________________.

3MAIN BRANCHES OF CHEMISTRYOrganic Chemistry

Inorganic Chemistry

Physical Chemistry

Analytical Chemistry

Biochemistry

Theoretical Chemistry 4SCIENTIFIC METHOD The scientific method is not a rigid set of rules, but a general guide for investigation or logical approach to finding answers to questions.Curiosity or a quest for knowledgeDesign and do experiments, collect data and information, establish facts, and make observationsOrganize and find relationship between information or data. Formulate a law, a statement of the relationships between facts, data, and observations.

5SCIENTIFIC METHOD CONTINUED 4. Draw conclusions from the observation, data, and facts. Formulate a hypothesis, a tentative explanation of a scientific law.5. Design new experiments based on the hypothesis, and collect more data, establish more facts, and make more observations.6. Update laws and hypothesis, ask new questions, and recycle to step 5.

6

Scientific ResearchPure Research- ______________________________________________________________.

Applied Research- ___________________________________________________________.

**** NOTE ****Science and Technology are ____ the same thing!Where science includes knowledge in whatever discipline youre in; technology is the application of that knowledge for practical purposes.Just a Quick Note Qualitative Data & Quantitative Data7MeasurementsScience involves making observations and measurements. These measurements involve two things: a number and a unit.

25.4 g8Units of MeasurementWe have an international system of measurement the __________. This is a system of measurement that the world has agreed upon.

We need to be aware however; that there is actually one more system called the __________; which stands for centimeter, gram, second.

9SI Base UnitsSome Basic Propertiescgs(subset of the metric system)SI SystemotherLength or distancecentimetermeterIn, yds, miTimesecondssecondshours, daysMassgramskilogramslb, ozKinetic EnergyErgJoule10Derived UnitsDerived units are _________________ of base units such as mass and volume.

Volume ________________________________.

Density ________________________________.11Unit ConsistencyExpress all units in the same unit of the system

Kinetic Energy= M V2

12UNIT CONVERSIONSIt is important, especially for unit consistency, that you are able to move back and forth between units of measurement.

Conversion Factors are NOT scary they are simply ratios that come from two things of different units which are equal to one another in magnitude!!

The chemistry is knowing where things go the solving is just algebra!13Dimensional AnalysisThe technique we use that allows us to convert from one unit of measurement to another, is ________________________.

____________________ a ratio of equal values used to go from one unit to another

Example:Can be written asWe Use This14Rules for Dimensional AnalysisALWAYS start with the _____________ !!!Draw a _____________ sign and a linePlace the unit to be canceled on the bottomPlace a _____________ on the line you have drawnCross out units and see what you have left. Do the math!#Ax---------#B#A//15Lets try an exampleLet s convert 32.5 inches to feet.

How many seconds are in 82.95 minutes?

Convert 65 miles per hour to kilometers per second. (0.625 miles = 1 Km)

Conversions with prefixes are done in exactly the same manner, you just have to know the prefixes!!16PrefixesKiloHectoDecaBasedecicentimilli10001001011/101/1001/1000micronanopico1/1000000(1 x 10-6)1/1000000000(1 x 10-9)1/1000000000000(1 x 10-12)These larger units are multiplications of the base. For example a kilometer is 1000 meters.These smaller units are fractions of the base. For example a centimeter is a 100th of a meter.17NumbersThere are two types of numbers in the world1.) ExactExample: Sample size or n

2.) Nonexact: measurments18Measurement and Significant FiguresAll measurements have some uncertainty:the accuracy and precision of the measuring devicethe skill of the operatorthe uncertainty principle19

ACCURACY VS. PRECISIONAccuracy: How closely the measured value is to the true value

Precision: How closely the measured values are to one another

20MEASURE OF ACCURACY% Error =I correct value measured value Icorrect valueX 100

21Uncertainty

There is uncertainty in every measurement we take. We are limited not only by the instruments we use, but also by our own physical limitations. Scientists have devised a way to communicate our limitations in a way that we can all have an idea to how much uncertainty there is in a number simply by looking at it!22Significant FiguresScientist use significant figures to determine how precise a measurement is.

Significant digits in a measurement include all of the known digits plus one estimated digit .23For exampleLook at the ruler below

What would be the measurement in the correct number of sig figs?

24Lets try this oneLook at the ruler below

What would be the measurement in the correct number of sig figs?

25The same rules apply with all instrumentsRead to the last digit that you know

Estimate the final digit26Lets try graduated cylindersLook at the graduated cylinder below

What would be the measurement in the correct number of sig figs?

27One more graduated cylinderLook at the cylinder below

What would be the measurement in the correct number of sig figs?

28Rules for Significant figuresRule #1All non zero digits are ALWAYS significant

How many significant digits are in the following numbers?27425.6328.98729Rule #2Zeros are ONLY significant if they meet the following criteria:1.) they are between non-zero digits2.) they are at the end of a number AND to the right of the decimal

How many significant digits are in the following numbers?504.06002

9.077

5.00

0.00361

2.0100

30Rules Continued All zeros that act as place holders are NOT significant these are zeros in front of the number or zeros at the end of a number with no decimal.

Numbers with zeros at the end and no decimal can be made significant by adding a decimal 2000. or 30.

31For example0.00026.02 x 1023100.000150000800__________________________ _____________ _____________ _____________

How many significant digits are in the following numbers?32Rule #5All counting numbers and constants have an infinite number of significant digits in other words, you do not have to worry about them when performing calculations.For example: 1 hour = 60 minutes12 inches = 1 foot24 hours = 1 dayThere are 30 students in the class33How many significant digits are in the following numbers?0.0073100.02025007.90 x 10-3670.00.0000118.84__________________________ _____________ __________________________ _____________ _____________ 34RULES FOR THE COMBINATION OF SIGNIFICANT DIGITS1. Addition and Subtraction Round to the least decimal placeAdd: 23.67 + 9.5= 33.17 33.22. Multiplication and Division Round to the least significant digit(2.34 x 3.2)/ 5.22= 1.434482 1.4

35What happens when to have the appropriate amount of significant figures, you need to round???200.99(want 3 SF)

18.22(want 2 SF)

135.50(want 3 SF)

0.00299(want 1 SF)

98.59(want 2 SF)3699.3434000.10.000375

0.0234

94577.1Place the following numbers in scientific notation with 3 SFs:What happens when to have the appropriate amount of significant figures, you need to use Scientific notation???37