Chemistry, The Central Science, 12th or LSU edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 1 Introduction: Matter and Measurement KR Matter And Measurement Roadmap: • Physical Objects (bodies, things) Matter, RadiationMatter as atoms, moleculesMatter as electrons, protons, neutrons….Matter properties • Chemistry Science, Chemistry interested in structure and change of matter and its properties • Science Practical aspects (units, Matter And conversions) Measurement The Chemical View of Things: Matter • Matter is the physical material of the universe. It occupies space, has specific properties (like mass) that can be observed and measured. • Matter: Some elementary material objects (electrons, protons, neutrons) combine to form elementary substances, atoms of elements, molecules, ions etc. • Modern chemistry works at molecular level. Intelliome-Prentice Hall Matter And 3 Measurement Chemistry In this science we study matter and the changes it undergoes. Matter And © 2009, PrenticeMeasurement Hall, Inc. What is Chemistry? • What chemists often try to do is to find the relationships between the structure of matter and the properties of matter we observe • Chemistry is the science that seeks to understand what matter is and what it does by studying what atoms and molecules and the subatomic objects do. In practice, chemistry is different than physics. Intelliome-Prentice Hall Matter And 5 Measurement The Scientific Method • A process for trying to understand nature by observing nature and the way it behaves, and by conducting experiments to test our ideas. • Key Characteristics of the Scientific Method include Observation, formulation of Hypotheses, Experimentation and formulation of Intelliome-Prentice Hall Laws and Theories Matter And 6 Measurement Scientific Method The scientific method is simply a systematic approach to solving problems. Matter And © 2009, PrenticeMeasurement Hall, Inc. Scientific method- a visual presentation: Intelliome-Prentice Hall Matter And 8 Measurement Laws • Summary of observations that combines some past observations into one general statement about those observations – Law of Conservation of Mass – “In a chemical reaction matter is neither created nor destroyed.” • Allows you to predict future observations – So you can test the Law with experiments • Like in any law, improved experiments and new knowledge could indicate violations and/or extensions of previous scientific Intelliome-Prentice Hall laws Matter And 9 Measurement CHEMISTRY and CHEMICAL IN THE USA • • • • • http://www.doe.gov http://www.nsf.gov http://www.nist.gov http://www.epa.gov http://www.nih.gov Intelliome-Prentice Hall Matter And 10 Measurement Units of Measurement Matter And Measurement What is a Measurement? • quantitative observation • comparison to an agreed upon standard • every measurement has a number and a unit Project: measuring global temperatures Prentice HAll-Intelliome Matter And 12 Measurement A Measurement • the unit tells you what standard you are comparing your object property (observable) to • the number tells you 1.what multiple of the standard the object measures 2.the uncertainty in the measurement (the procedure for the estimate of uncertainty we will see later) Matter Prentice HAll-Intelliome And 13 Measurement SI Units • Système International d’Unités • Uses a different base unit for each quantity Matter And Measurement Metric System Prefixes convert the base units into units that are appropriate for the item being measured. Matter And Measurement Volume • The most commonly used metric units for volume are the liter (L) and the milliliter (mL). □ A liter is a cube 1 dm long on each side. □ A milliliter is a cube 1 cm long on each side. Matter And Measurement Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy. Matter And Measurement Temperature: A measure of the average kinetic energy of the particles in a sample. Matter And Measurement Temperature • In scientific measurements, the Celsius and Kelvin scales are most often used. • The Celsius scale is based on the properties of water. □ 0C is the freezing point of water. □ 100C is the boiling point of water. Matter And Measurement Temperature • The Kelvin is the SI unit of temperature. • It is based on the properties of gases. • There are no negative Kelvin temperatures. • K = C + 273.15 Matter And Measurement Temperature • The Fahrenheit scale is not used in scientific measurements. • F = 9/5(C) + 32 • C = 5/9(F − 32) Matter And Measurement Density: Physical property of a substance m d= V Matter And Measurement Uncertainty in Measurement Matter And Measurement Estimating the Last Digit • for instruments marked with a scale, you get the last digit by estimating between the marks – • if possible mentally divide the space into 10 equal spaces, then estimate how many spaces over the indicator is Prentice HAll-Intelliome 1.2 grams Matter And 24 Measurement Accuracy versus Precision • Accuracy refers to the proximity of a measurement to the true value of a quantity. • Precision refers to the proximity of several measurements to each other. Matter And Measurement Significant Figures • The term significant figures refers to digits that were measured. • When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers. Matter And Measurement Significant Figures: use exponential notation, or 1. All nonzero digits are significant. 2. Zeroes between two significant figures are themselves significant. 3. Zeroes at the beginning of a number are never significant. 4. Zeroes at the end of a number are significant if a decimal point is written Matter in the number. And Measurement Significant Figures • When addition or subtraction is performed, answers are rounded to the least significant decimal place. • When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation. Matter And Measurement Significant Figures Writing Numbers to Reflect Precision Matter And Measurement Reporting Measurements • measurements are written to indicate the uncertainty in the measurement • the system of writing measurements we use is called significant figures • when writing measurements, all the digits written are known with certainty except the last one, which is an 45.872 estimate estimated certain Prentice HAll-Intelliome Matter And 30 Measurement Dimensional Analysis • We use dimensional analysis to convert one quantity to another. • Most commonly dimensional analysis utilizes conversion factors (e.g., 1 in. = 2.54 cm) 1 in. 2.54 cm or 2.54 cm 1 in. Matter And © 2009, PrenticeMeasurement Hall, Inc. Dimensional Analysis Use the form of the conversion factor that puts the sought-for unit in the numerator. Given unit Conversion factor desired unit given unit desired unit Matter And © 2009, PrenticeMeasurement Hall, Inc. Dimensional Analysis • For example, to convert 8.00 m to inches, – convert m to cm – convert cm to in. 100 cm 1 in. 8.00 m 315 in. 1m 2.54 cm Matter And © 2009, PrenticeMeasurement Hall, Inc.