Lecture Presentation Chapter 1 Introduction: Matter and Measurement John D. Bookstaver St. Charles Community College Cottleville, MO Contents Classification of matter Properties and change of matter Units of measurements Uncertainty in measurements Dimensional analysis Chemistry In this science we study matter, its properties, and its behavior. Matter We define matter as anything that has mass and takes up space. • A pure substance (usually referred to simply as a substance) is matter that has distinct properties and a composition that does not vary from sample to sample. © 2012 Pearson Education, Inc. Matter • A compound is made of two or more different kinds of elements. • Mixtures are combinations of two or more substances in which each substance retains its chemical identity. © 2012 Pearson Education, Inc. Matter • Atoms are the building blocks of matter. • Each element is made of the same kind of atom. © 2012 Pearson Education, Inc. Matter electrolysis of water copper sulfate solution © 2012 Pearson Education, Inc. States of Matter © 2012 Pearson Education, Inc. • A gas (also known as vapor) has no fixed volume or shape; rather, it uniformly fills its container. A gas can be compressed to occupy a smaller volume, or it can expand to occupy a larger one. • A liquid has a distinct volume independent of its container, and assumes the shape of the portion of the container it occupies. • A solid has both a definite shape and a definite volume. © 2012 Pearson Education, Inc. Classification of Matter Matter And Measurement Exercise © 2012 Pearson Education, Inc. Properties and Changes of Matter © 2012 Pearson Education, Inc. Types of Properties • Physical Properties… – Can be observed without changing a substance into another substance. ◦ Boiling point, density, mass, volume, etc. • Chemical Properties… – Can only be observed when a substance is changed into another substance. ◦ Flammability, corrosiveness, reactivity with acid, etc. © 2012 Pearson Education, Inc. Types of Properties • Intensive Properties… – Are independent of the amount of the substance that is present. ◦ Density, boiling point, color, etc. • Extensive Properties… – Depend upon the amount of the substance present. ◦ Mass, volume, energy, etc. © 2012 Pearson Education, Inc. Types of Changes • Physical Changes – These are changes in matter that do not change the composition of a substance. ◦ Changes of state (solid – liquid – gas) temperature, volume, etc. • Chemical Changes – Chemical changes result in new substances. ◦ Combustion, oxidation, decomposition, etc. © 2012 Pearson Education, Inc. Chemical Reactions In the course of a chemical reaction, the reacting substances are converted to new substances. © 2012 Pearson Education, Inc. Chemical Reactions The chemical reaction between a copper penny and nitric acid. © 2012 Pearson Education, Inc. Separation of Mixtures © 2012 Pearson Education, Inc. Filtration In filtration, solid substances are separated from liquids and solutions. Distillation Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components. Chromatography This technique separates substances on the basis of differences in solubility in a solvent. Chromatography Separation of three substances using column chromatography © 2012 Pearson Education, Inc. Units of Measurement © 2012 Pearson Education, Inc. SI Units • Système International d’Unités • A different base unit is used for each quantity. Metric System Volume • The most commonly used metric units for volume are the liter (L) and the milliliter (mL). – A liter is a cube 1 decimeter (dm) long on each side. – A milliliter is a cube 1 centimeter (cm) long on each side. © 2012 Pearson Education, Inc. Temperature- measurement of of the average kinetic energy F = 9/5(C) + 32 K = C + 273.15 • 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. Derived Units A derived unit is obtained by multiplication or division of one or more of the base units. the SI unit for speed—m/s, read “meters per second”—is a derived unit, the SI unit for distance (length), m, divided by the SI unit for time, s. Two common derived units in chemistry are those for volume and density. Uncertainty in Measurement © 2012 Pearson Education, Inc. Uncertainty in Measurements equipment errors Inexact numbers in measurement human errors Uncertainties always exist in measured quantities. Uncertainty in Measurements Uncertainty in Measurements © 2012 Pearson Education, Inc. 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. To get more precision, which ruler would you choose? A B C Ruler A is marked off every 0.05 cm Ruler B is marked off every 0.1 cm Ruler C is marked off every 0.5 cm Significant Figures • The term significant figures refers to digits that were measured, include all known digits plus one estimated digit • When rounding calculated numbers, we do not overstate the accuracy of our answers. (least sf) 0.0025 2sf - leading zeros are not significant figures 1.003 4sf – captive zeros are sf 1.00*102 - 3 sf trailing zeros after the a decimal point is sf 100. - 3sf 100 - 1sf without decimal point, not sf 1 in = 2.54 cm Exact numbers(from counting or definition) – infinite sf (just ignore the sf) Significant Figures in calculations When carrying measured quantities through calculations, the least certain measurement limits the certainty of the calculated quantity and thereby determines the number of significant figures in the final answer. Exercise © 2012 Pearson Education, Inc. 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. Dimensional Analysis Use the form of the conversion factor that puts the sought-for unit in the numerator: desired unit given unit Given unit desired unit Conversion factor © 2012 Pearson Education, Inc. Dimensional Analysis • For example, to convert 8.00 m to inches(1 in. = 2.54 cm) – convert m to cm – convert cm to in. 100 cm 1 in. 8.00 m 315 in. (3sf) 1m 2.54 cm The average speed of a nitrogen molecule in air at 25 C is 515 m/s, convert this speed to mile per hour. 1 mi = 1.6093 km
