CHEMISTRY July 30, 2013

Brain Teaser Turn in Homework: Science Autobiography Write your name and period number Define Chemistry using your own words What is the SI base unit for the following measurements (Example: Volume = Liter (L)) Length = ___________ Mass = __________ Temperature = ___________ Time = __________

Agenda Brain Teaser Notes: Homework Introduction to Chemistry SI Units and Base Units Significant Figures Homework Intro to Measurement Worksheet 1 Significant Figures Worksheet (?)

Unit 1 Objectives Introduction to Chemistry Define chemistry and matter Units of measurement SI Units Base Units Accuracy versus Precision Uncertainty in Measurement Significant Figures Significant Figures in Calculations Dimensional Analysis

Introduction to Chemistry Chemistry: The Central Science Chemistry is the science that investigates and explains the structure and properties of matter. Seeks to explain the submicroscopic events that lead to macroscopic observations

Branches of Chemistry Branch Area of Emphasis Examples Organic chemistry most carbon-containing chemicals pharmaceuticals, plastics Inorganic chemistry in general, matter that does not contain carbon minerals, metals and nonmetals, semi-conductors Physical chemistry the behavior and changes of matter and the related energy changes reaction rates, reaction mechanisms Analytical chemistry components and composition of substances food nutrients, quality control Biochemistry matter and processes of living organisms metabolism, fermentation

SI Units (Le Systéme Internationale) Units of measurement SI Units (Le Systéme Internationale) Scientists need to report data that can be reproduced by other scientists. They need standard units of measurement. Base Units Le A base unit is a defined unit in a system of measurement There are seven base units in SI. 7

Base Units Official definitions of the seven base units http://www.unc.edu/~rowlett/units/sifundam.html 8

Metric staircase 9

SI Units and Base Units Handouts Kilo, centi, milli

SIGNIFICANT FIGURES

Significant Figures Significant Figures Digits in a measurement that have meaning relative to the equipment being used 12

Significant Figures Place What is the increment on the equipment? What you know for sure. 13

Significant Figures Digits with meaning Digits that can be known precisely plus a last digit that must be estimated. 14

Scale Reading and Uncertainty Uncertainty: Limit of precision of the reading (based on ability to guess the final digit). Existed in measured quantities versus counted quantities Refer to Example (2 rulers) Addition and substraction(no. of sig. figs) Division and Multiplication (no. of sig. figs)

Ruler http://www.funbrain.com/measure/ What are the units?

Graduated Cylinder http://www.uwplatt.edu/chemep/chem/chemscape /labdocs/catofp/measurea/volume/gradcyl/gradc yl.htm What are the units?

Significant Figures What do you notice? Depends on type of equipment being used. Depends on size of equipment used. 19

Summary Things to consider What do significant figures tell you about the measurement on the equipment? If you wanted to measure the mass of a whale, what scale would you want to use? Would it matter if you know its mass accurately to 1 gram? If you wanted to measure the mass a grain of sand , what scale would you want to use? Would it matter if you know its mass accurately to 1 gram? 20

Significant Figures Raw Data Rules All digits 1-9 are significant. How do you know how many sig figs? All digits 1-9 are significant. Zeros between significant digits are always significant. Trailing 0’s are significant only if the number contains a decimal point Zeros in the beginning of a number with a decimal point are not significant. Zeros following a significant number with a decimal are significant. 21

Significant Figures Pacific to Atlantic Rule Examples Pacific = Decimal Present Start from the Pacific (left hand side), every digit beginning with the first 1-9 integer is significant 20.0 = 3 sig digits 0.00320400 = 6 sig digits 1000. = 4 sig digits 22

Significant Figures Atlantic Rule to Pacific Examples Atlantic = Decimal Absent Start from the Atlantic (right hand side), every digit beginning with the first 1-9 integer is significant 100020 = 5 sig digits 1000 = 1 sig digits 23

Practice How many significant figures are in 400.0 4000 4004 0.004 24

More Practice Problems Determine the number of significant figures in the following: 1005000 1.005 0.000125 1000. 0.02002 2002 200.200

Review Questions Determine the number of significant figures in: 4.05 x 105 g 4500. g

Homework Measurement Worksheet 1 Significant Figures 1 Worksheet

THE END

Why do we use the metric system? Advantages Simple to use Easy to convert from one unit to another Dimensional Analysis Universal – used worldwide By all scientists to communicate By all industrialized nations Except United States U.S. loses billions of dollars in trade

Mass versus Volume Question: What is the difference between mass and volume?

Introduction to Chemistry Chemistry: The Central Science A more formal definition of Matter is anything that takes up space and has mass Mass is the measure of the amount of matter that an object contains Volume is the amount of space an object takes up. Ask Question of two spherical object…which one has a larger volume?

Example Refer to the two identical spherical objects below Bowling Ball Volley Ball

Example Which of the following weighs more? A ton of feathers? A ton of bricks?

SI Units (Le Systéme Internationale) Units of measurement SI Units (Le Systéme Internationale) Scientists need to report data that can be reproduced by other scientists. They need standard units of measurement. Base Units Le A base unit is a defined unit in a system of measurement There are seven base units in SI.

Base Units Official definitions of the seven base units http://www.unc.edu/~rowlett/units/sifundam.html

Metric staircase

Why do we use the metric system? Advantages Simple to use Easy to convert from one unit to another Dimensional Analysis Universal – used worldwide By all scientists to communicate By all industrialized nations Except United States U.S. loses billions of dollars in trade

Example Convert 3400 milliliters to liters 44 centimeters to meters 277 kilograms to grams

Accuracy Versus Precision What is the difference between accuracy and precision?

Precision versus Accuracy Precision: is a measure of how closely an individual measurements agree with one another Can be precise but inaccurate Accuracy: refers to how closely individual measurements agree with the correct, or “true” value Examples using the dartboard

An archery target illustrates the difference between accuracy and precision.

Accuracy and Precision Measurements

Scale Reading and Uncertainty Uncertainty: Limit of precision of the reading (based on ability to guess the final digit). Existed in measured quantities versus counted quantities Addition and substraction(no. of sig. figs) Division and Multiplication (no. of sig. figs)

Example Which electronic balance below allows you to obtain a more precise measurement? Why? Tenth versus hundred precision…it is more precise. A B

Triple Beam Balance http://www.wisc- online.com/objects/index_tj.asp?objID=GCH202 What are the units?

Ruler http://www.funbrain.com/measure/ What are the units?

Graduated Cylinder http://www.uwplatt.edu/chemep/chem/chemscape /labdocs/catofp/measurea/volume/gradcyl/gradc yl.htm What are the units?

Measurement Activity Objectives Measure each physical quantity to the maximum accuracy allowed by the appropriate instrument. Record measurements and calculations with the appropriate units from the international system of units (SI.)

Measurement Activity Set up assignment Station Rotation Title, Name, Chemistry, Period, Date Station Rotation 10 Station 3-4 minutes at each station Refer to Handout Do NOT remove any items from the station Clean Up and Restore each station before switching

Homework Homework “Is it worth the risk?” worksheet Sign Lab Safety Contract Study for Lab Safety Test (Monday) Get Supplies for Chemistry

Closure Reflect on your learning during the lab activity Concepts learned? “Ah-ha” moments? Questions?

Significant Figures

Rules for zeros: All zeros count except placeholder zeros These are the ones that disappear when you write the number in scientific notation. Zeros between nonzero digits are always significant E.g. 1005 kg (4 sig. fig) and 1.03 (3 sig. fig) Zeros at the beginning of a number are never significant E.g. 0.02 (1 sig. fig) and 0.0026 (2 sig. fig) Zeros at the end of a number are significant if the number contains a decimal point 0.0200g (3 sig. fig), 3.0 cm (2 sig. fig), 5000 (1 sig. fig)

Rules for recognizing significant figures Non-zero numbers are always significant. Zeros between non-zero numbers are always significant. All final zeros to the right of the decimal place are significant. Zeros that act as placeholders are not significant. Counting numbers and defined constants have an infinite number of significant figures.

Review Questions Determine the number of significant figures in the following: 1005000 1.005 0.000125 1000. 0.02002 2002 200.200

Review Questions Determine the number of significant figures in: 4.05 x 10^5 g 4500. g

Closure Reflect on your learning today

Homework Measurement Worksheet 2 Science Safety Test Element Quiz Wednesday = TOMORROW Element Quiz Thurs/Fri Lab Notebook Quadrille Lab Notebook (Graphing paper) OR Carbonless Copy Lab Notebook

Topics on Unit 1 Test Lab Safety Measurements SI units Significant Figures, Uncertainty Accuracy and Precision Understanding Equipments Dimensional Analysis

Intro to Dimensional Analysis