Intro to math and sig figs.notebook. August 28, 2016

Transcription

1 Reminder Honors Expectations: You are responsible for reading all chapters, knowing alll vocab terms, and completing all problem sets. Chapter 1 and 2 are basic/intro you need to read them because on your test (scientific method and terms). We will begin Chapter 3 today... From early eras, alchemists developed techniques and tools that scientists still use today. Today's chemists provide logical explanations for observations! Chemistry became what it is today with help of Antonie Lavoisier in 1500s Combustion Analysis Law of Conservation of Mass A Measurement includes a quantity and a unit! ~ We use SI units for consistency SI = International System of Msmt Base quantity: Name: Symbol: length meter m mass kilogram kg time second s electric current ampere A temperature kelvin K amount of substance mole mol luminous intensity candela cd volume liter L or ml Measure temperature in degrees Celsius instead of Fahrenheit... But we will work with Kelvin a LOT Kelvin = Celsius ( o C) Temps to know: Room Temp = 25 o C Body Temp = 37 o C Water boiling = 100 o C Water freezing = 0 o C Examples of SI derived units: Must complete a calculation density = mass/volume area = meters 2 1

2 Kilo Hecto Deca base deci centi milli Using the Metric System: Know your Prefixes! We deal with very large #s and very small #s So use Scientific Notation for convenience: - Product of coefficient and 10 x ex: How would you write in exponential notation? 6.02 x King Henry Died by Drinking Chocolate Milk M.. K D b d c m.... n.. p Convert 53g to kg Convert 9.84 L to dl Exponential Notation: Express the following numbers in exponential/scientific notation Express the following numbers in the long form x x , x x x x

3 Accuracy- how close to actual/true value Precision - how close series of msmts are to one another Error- difference between accepted value and experimental value (take the abs value) Percent Error=l experimental value - accept valuel x 100 accepted value The BEST EVER Explanation of precision and accuracy!!!! Precision is an indication of the reproducibility of a measurement. It does not necessarily reflect the nearness of a measured quantity to the true value. Suppose that a student massed an object three times and obtained masses of 3.54g, 3.55g and 3.56g. The precision here is good. Accuracy is an indicator of the nearness of a measured quantity to the true value. Accuracy is restricted by the number of significant figures recorded for a measurement and these are limited by the tool used to make the measurement. Ex: You measure room temp to be 28 o C with your thermometer. What is percent error? True or False? There is always uncertainty in measurements. * Need 3 volunteers! What is a significant figure/digit? (next slide) USING SIGNIFICANT FIGURES IN CHEMISTRY We want the most accurate values we can measure, but will estimate one digit... Significant figures - include all digits that are known plus an additional estimated digit - accuracy depends on msmt appartus scale (m vs cm vs mm)

4 Determining the number of Sig figs in a measurement: ALREADY ON YOUR LECTURE NOTES!! Pacific Atlanc Method for Significant Figures If the decimal is Present.approach the number from the Pacific. Go to the first non zero digit; that and every number to the right of it is significant. If the decimal is Absent approach the number from the Atlanc. Go to the first non zero digit; that and every number to the le of it is significant. Examples: a. 40.7L b kg c. 32,006 m d cm 3 e cm 3 f m 2 g g h i ml YOU TRY! 4

5 Attachments Mathematics of Chemistry.pptx Lab Group MSDS Overview.docx Chem Lab equipment review.notebook Mathematics of Chemistry filled 8.31.pptx Key PS 3A.docx