CHEMISTRY July 31st, 2012

Brain Teaser: Dollar Bill 2 What do think will happen if I dip a dollar bill in a 50% ethanol solution and light it on fire? Why? Demo Record Observations Was your prediction correct? Explain the science behind this

Agenda Brain Teaser Demo: Dollar Bill Lecture: Homework 3 Brain Teaser Demo: Dollar Bill Lecture: Introduction to Chemistry SI Units and Base Units Significant Figures Homework Intro to Measurement Worksheet

Unit 1 Objectives Introduction to Chemistry 4 Define chemistry and matter Units of measurement SI Units Base Units Accuracy versus Precision Uncertainty in Measurement Significant Figures

Introduction to Chemistry 5 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 6 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 7 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 8 Official definitions of the seven base units http://www.unc.edu/~rowlett/units/sifundam.html

9 Metric staircase

10 SIGNIFICANT FIGURES

Significant Figures Significant Figures 11 Significant Figures Digits in a measurement that have meaning relative to the equipment being used

Significant Figures Place What is the increment on the equipment? 12 Place What is the increment on the equipment? What you know for sure.

Significant Figures Digits with meaning 13 Digits with meaning Digits that can be known precisely plus a last digit that must be estimated.

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Ruler 15 http://www.funbrain.com/measure/ What are the units?

Graduated Cylinder 16 http://www.uwplatt.edu/chemep/chem/chemsc ape/labdocs/catofp/measurea/volume/gradcyl/ gradcyl.htm What are the units?

Significant Figures What do you notice? 17 What do you notice? Depends on type of equipment being used. Depends on size of equipment used.

Significant Figures Raw Data Rules All digits 1-9 are significant. 18 Raw Data Rules 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.

Significant Figures Pacific to Atlantic Rule Pacific = Decimal Present 19 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

Significant Figures Atlantic Rule to Pacific Atlantic = Decimal Absent 20 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

Practice 21 How many significant figures are in 400.0 4000 4004 0.004

Rally Rows How many significant figures are in 0.02 0.020 501 501.0 22 How many significant figures are in 0.02 0.020 501 501.0 5000 5000. 5050 01.0050 50300 5.0300

Review Questions 23 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: 24 Determine the number of significant figures in: 72.3 g 60.5 g 6.20 g 0.0253 g 4320 g 0.00040230 g 4.05 x 10^5 g 4500. g

Why do we use the metric system? 25 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