Chapter 1 Introduction: Matter and Measurement 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 K R

Roadmap: Physical Objects (bodies, things) Matter, RadiationMatter as atoms, moleculesMatter as electrons, protons, neutrons….Matter properties Chemistry  Science, Chemistry interested in structure and change of matter and its properties Science  Practical aspects (units, conversions)

Intelliome-Prentice Hall 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

Chemistry In this science we study matter and the changes it undergoes. © 2009, Prentice-Hall, Inc.

Intelliome-Prentice Hall 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

Intelliome-Prentice Hall 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 Laws and Theories Intelliome-Prentice Hall

Scientific Method The scientific method is simply a systematic approach to solving problems. © 2009, Prentice-Hall, Inc.

Scientific method- a visual presentation: Intelliome-Prentice Hall

Intelliome-Prentice Hall 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 laws Intelliome-Prentice Hall

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

Units of Measurement

Prentice HAll-Intelliome 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

Prentice HAll-Intelliome A Measurement the unit tells you what standard you are comparing your object property (observable) to the number tells you what multiple of the standard the object measures the uncertainty in the measurement (the procedure for the estimate of uncertainty we will see later) Prentice HAll-Intelliome

SI Units Système International d’Unités Uses a different base unit for each quantity

Metric System Prefixes convert the base units into units that are appropriate for the item being measured.

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.

Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy.

Temperature: A measure of the average kinetic energy of the particles in a sample.

Temperature In scientific measurements, the Celsius and Kelvin scales are most often used. The Celsius scale is based on the properties of water. 0C is the freezing point of water. 100C is the boiling point of water.

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

Temperature The Fahrenheit scale is not used in scientific measurements. F = 9/5(C) + 32 C = 5/9(F − 32)

Physical property of a substance Density: Physical property of a substance d= m V

Uncertainty in 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 1.2 grams Prentice HAll-Intelliome

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.

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.

Significant Figures: use exponential notation, or All nonzero digits are significant. Zeroes between two significant figures are themselves significant. Zeroes at the beginning of a number are never significant. Zeroes at the end of a number are significant if a decimal point is written in the number.

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.

Writing Numbers to Reflect Precision Significant Figures Writing Numbers to Reflect Precision

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 estimate 45.872 certain estimated 45.872 Prentice HAll-Intelliome

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 2.54 cm 1 in. or © 2009, Prentice-Hall, Inc.

Dimensional Analysis Use the form of the conversion factor that puts the sought-for unit in the numerator. Given unit   desired unit desired unit given unit Conversion factor © 2009, Prentice-Hall, Inc.

Dimensional Analysis For example, to convert 8.00 m to inches, convert m to cm convert cm to in. 100 cm  1 m  1 in. 2.54 cm  315 in. 8.00 m © 2009, Prentice-Hall, Inc.