Ch 1 Introduction Matter and Measurement Chemistry The study of matter and the changes that matter undergoes 1 1 The Study of Chemistry The Atomic and Molecular Perspective of Chemistry Matter Anything that has mass and occupies space Property Any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types Elements About 100 substances that compose matter Atoms Smallest building blocks of matter Properties of matter relate to the types of atoms composition and their arrangements structure Molecules Two or more atoms joined in specific shapes Macroscopic realm and submicroscopic realm to be analyzed Why Study Chemistry Chemistry is part of health care natural resource conservation the environment and energy supply 1 2 Classifications of Matter Matter characterized by physical state solid liquid or gas and composition element compound or mixture States of Matter States of matter Gas liquid or solid Gas vapor No fixed volume or shape can be compressed or expanded o Molecules far apart and moving at high speeds o When compressed frequency of molecule collision is increased Liquid Distinct volume assumes shape of container it occupies o Molecules packed together moving rapidly sliding over each other Solid Definite shape and definite volume o Molecules tightly together Pure Substances Most substances are not chemically pure but can be separated into pure substances Pure substance or substance Matter with distinct properties and a composition that does not vary from sample to sample ex Water All substances are elements or compounds Elements Substances that cannot be decomposed into simper substances o Each element has only one kind of atom Compounds Substances composed of two or more elements Mixtures Combinations of two or more substances in which each substance retains its chemical identity Elements 118 known elements varying greatly in abundance Symbol for each element has two letters with first capitalized Periodic table Compounds Most elements interact with other elements to form compounds Ex Hydrogen gas burns in oxygen gas to form water Pure water consists of 11 hydrogen and 89 oxygen by mass H and O exist as diatomic molecules Law of constant composition definite proportions The elemental composition of a compound is always the same o French chemist Joseph Louis Proust in 1800 o Pure compounds have same composition and properties under same conditions regardless of source Mixtures Each substance in mixture retains its chemical identity and properties Unlike pure substance fixed composition composition of mixtures varies Components Substances within a mixture Heterogeneous Vary in composition properties and appearance Homogeneous Uniform mixtures also called solutions 1 3 Properties of Matter Physical properties Properties able to be observed without changing the identity and composition of the substance ex Color odor density melting point boiling point and hardness Chemical properties Describe the way a substance changes or reacts to form other substances ex flammability Intensive properties Do not depend on amount of sample examined used to identify substances ex temp melting point Extensive properties Depend on amount of sample ex mass volume Physical and Chemical Changes Physical change Substances changes physical appearance but not composition All changes of state are physical changes Chemical change reaction Substance transformed into chemically diff substance Separation of Mixtures Difference in properties of substances is used o Use of magnet o Filtration Dissolve one of the substances o Distillation Separation by heating then condensation o Chromatography Depends on ability of substances to adhere to the surfaces of solids 1 4 Units of Measurements Many properties of matter are quantitative or associated with numbers Units must be specified and must be of the metric system Scientific Method Theory Model with predictive powers that accounts for all scientific observations o Always possibility of flaws o An explanation of what occurs in nature Scientific law A statement of what repeatedly occurs in nature SI Units SI units Metric unites used in scientific measurements from French Systeme International d Unites Seven base units Prefixes used to indicate decimal fractions or multiples of various units Length and Mass Mass Measure of the amount of material in an object SI unit of length is meter and that of mass is kilogram Temperature Temperature Measure of the hotness or coldness of an object Physical prop that determines heat flow Heat flows from high to low temperatures Celsius scale 0 C as water s freezing point and 100 C as boiling point Kelvin scale SI temp scale using Kelvin or K o o Zero on kelvin is absolute zero the lowest attainable temp K C 273 15 o C F 32 o 5 9 9 F C 32 5 Derived SI Units Derived unit Unit obtained by multiplication or division of one or more of the base units Ex Speed unit m s Volume Ex length cubed 1 L 1 dm3 1 mL 1 cm3 Syringes burettes and pipettes have greater precision with measuring liquids Density Density The amount of mass in a unit volume of a substance o Density mass volume Expressed as g cm3 or g mL Density of water 1 00 g mL Density is temp dependent Chemistry in the New Clean energy from fuel cells energy of chemical reaction converted directly into electrical energy Regulation of greenhouse gases o Greenhouse gases Substances with the potential to alter global climate bc of ability to trap long wavelength radiation at Earth s surface Anesthesia o Injected into blood stream for medical procedures o Drugs have therapeutic index or ration of smallest fatal dose to smallest dose that gives the desired effect 1 5 Uncertainty in Measurement Exact numbers Values are known exactly Inexact numbers Values with some uncertainty o Numbers obtained by measurement always inexact Precision and Accuracy Precision Measure of how closely individual measurements agree with each other Accuracy How closely individual measurements agree with the correct true value Standard deviation Reflects how much individual measurements differ from average Significant Figures Significant figures All digits of a measured quantity including uncertain one Greater number of sig figs greater precision Rules o Zeros between nonzero digits are always significant o Zeros at beginning of number are never significant o Zeros at end of number are significant o Zeros at end of number when there s no decimal are not