Chapter 2, 3, & 4 (Through January 22nd, 2016)
Chapter 2, 3, & 4 (Through January 22nd, 2016) 22075
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This 0 page Class Notes was uploaded by Michelle Notetaker on Friday January 22, 2016. The Class Notes belongs to 22075 at Wayne State University taught by Dr. Matti in Winter 2016. Since its upload, it has received 25 views. For similar materials see Chemical Skills and Reasoning in Chemistry at Wayne State University.
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Date Created: 01/22/16
Chapter 2 0 Density 0 Mass of substance per unit of volume of the substance 0 Common units are gcmquot3 or gmL I cmquot3 mL 0 Density MassVolume I Water displacement 0 Placing objects into water and seeing how much the water displaces it Chapter 3 0 Dark Matter 0 Make up most of all matter on Earth 0 Baryonic matter 0 Dark matter doesn t absorb light 0 Exerts a force 0 Ex Black holes I Matter 0 Anything occupying space and having mass 0 Matter exists in 3 states I Solid 0 Rigid I Has a fixed volume and shape I Liquid 0 Has definite volume I Assumes shape of container I Gas 0 Has no fixed volume or shape I Takes the shape of volume of its container I Plasm stars lightning tail of comet 0 PropertiesChanges of Matter 0 Matter undergoes two types of propertieschanges I Physical I Chemical 0 Physical properties are properties observed Without changing the chemical composition I Characteristics that are directly observable and unique to a substance 0 Ex Odor color volume state solid liquid or gas density melting point and boiling point 0 Chemical properties I A substance s ability to form new substances I The characteristics that determine how the composition of matter changes as a result of contact with other matter or the in uence of energy I Characteristics that describe the behavior of matter 0 Ex Flammability rusting of steel and the digestion of food 0 Physical and Chemical Properties and Changes 0 Physical Change I Change in one or more physical properties of a substance not in its chemical composition 0 Ex boiling or freezing water changing states shredding paper dissolving sugar and water melting an ice cube 0 Chemical Change I A given substance becomes a new substance or substances with different properties and different composition 0 Ex Bunsen burner methane reacts with oxygen to form carbon dioxide and water 0 Best way to tell the difference between physical and chemical changes is to look at the chemical formula 0 Elements and Compounds 0 Element A substance that cannot be broken down into other substances I Ex Iron aluminum oxygen hydrogen 0 All of the matter in the world around us contains elements 0 Compound a substance composed of a given combination of elements that can be broken down into those elements by chemical methods I Ex Water carbon dioxide table sugar 0 A compound always contains atoms of different elements 0 A compound always has the same composition same combination of atoms 0 Mixtures vs Pure Substances 0 Pure substances always have the same composition I Either elements of compounds I Ex Water carbon dioxide gold 0 Mixtures have variable composition I mixtures are comprised of two or more pure substances I Ex Wood wine and coffee I Can be separated into pure substances elements andor compounds I Homogeneous mixture 0 Same throughout 0 Consists of visibly indistinguishable parts I A solution 0 Does not vary in composition from one region to another I Heterogeneous mixture 0 Consists of visibly distinguishable parts 0 Contains regions that have different properties from those of other regions Chapter 4 0 Background 0 Elements come from our stars 0 Scientists have taken it farther and have created even more elements 0 Elements come from other elements as well 0 Symbols of Elements 0 Each element has a unique one or twoletter symbol 0 First letter is always capitalized and the second is not 0 The symbol usually consists of the first one or two letters of the elements name 0 Sometimes the symbol is taken from the element s original Latin or Greek names 0 Dalton s Atomic Theory 0 Most natural materials are mixtures of pure substances 0 Pure substances are either elements or combinations of elements called compounds 0 A given compound always contains the same proportions by mass of the elements 0 Law of Constant Composition I A given compound always has the same composition regardless of where it comes from O Dalton s Atomic Theory 1808 I Elements are made of tiny particles called atoms TRUE I All atoms of a given element are identical NOT NECESSARILY TRUE I The atoms of a given element are different from those of any other element no 2 elements are the same I Atoms of one element can combine with atoms of other elements to form compounds A given compound always has the same relative numbers and types of atoms 0 Formulas of Compounds 0 Compound is a distinct substance that is composed of the atoms of two or more elements and always contains exactly the same relative masses of those elements 0 Chemical formulas expresses the types of atoms and the number of each type in each unit molecule of a given compound 0 Rules for Writing Formulas 0 Each atom present is represented by its element symbol 0 The number of each type of atom is indicated by a subscript written to the right of the element symbol 0 When one atom of a given type is present the subscript l is not written I S03 0 The Structure of the Atom 0 J J Thomson I Postulated the existence of electrons using cathoderay tubes I The atom must also contain positive particles that balance exactly the negative charge carried by particles that we now called electrons 0 William Thomson Plum Pudding Model I Reasoned that the atom might be thought of as a uniform pudding of positive charge with enough negative electrons scattered within the counterbalance that positive charge 0 Ernest Rutherford I Explained the nuclear atom I Atom has a dense center of positive charge called the nucleus I Electrons travel around the nucleus at a relatively large distance I A proton has the same magnitude of charge as the electron but its charge is positive 0 Rutherford and Chadwick I Most nuclei also contain a neutral particle called the neutron I A neutron is slightly more massive than a proton but has no charge 0 Atom Contents 0 Electrons found outside the nucleus negatively charged 0 Protons found in the nucleus positively charge equal in magnitude to the electron s negative charge 0 Neutrons found in the nucleus no charge virtually same mass as a proton O The nucleus is small compared with the overall size of the atom I Extremely dense account for almost all of the atom s mass 0 Chemical Properties 0 The chemistry of an atom arises from its electrons O Electrons are the parts of atoms that intermingle when atoms combine to form molecules 0 It is the number of electrons that really determines chemical behavior I Isotopes O Atoms with the same number of protons but different number of neutrons O Show almost identical chemical properties chemistry of atom is due to its electrons O In nature most elements contain mixtures of isotopes 0 Written AZX I A the mass number of protons of neutrons I Z atomic number of protons 0 The Periodic Table 0 The periodic table shows all of the known elements in order of increasing atomic number
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