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Unit 1 Structure of Matter The Known Universe • Everything in the known universe can be classified as either matter or energy. − Matter describes the physical things around us: the earth, the air you breathe, your pencil. − Energy is the ability to cause change or do work: including light, heat, electrical energy and mechanical energy, such as movement. Matter & Its Properties • The definition of matter has two parts − All matter has volume, which is the 3-D space an object occupies − All matter has mass, which is a measure of the amount of matter in an object. Properties & Changes: • There are 3 common states of matter − Solids have definite volume & definite shape o Particles are limited in their movement and packed close together − Liquids have definite volume but not definite shape o Particles are able to move around each other yet are still packed close together − Gases have neither definite vol. nor shape o Particles are independent of each other Properties & Changes: • There are 2 other states of matter that are not as widely acknowledged − Plasma is the result of superheating gases − Supersolid or superfluid is the result of super- cooling a solid (not much known about it so far, but lots of research possibilities) Classification of Matter • All forms of matter (no matter what it looks like) can be classified into one of two categories Classification of Matter • Two categories: − Pure substances o Are uniform in composition o Described by a chemical formula − Mixtures o Are composed of more than one component blended together o Different substances physically mixed together Classification of Matter: Pure Substances • A pure substance has a fixed composition − Every sample has exactly the same characteristics. − If they can be separated they can only be separated by chemical change (elements can not be broken down further) − Can be identified by a unique chemical formula: H, Ar, C, H2O, CO2, CH4, C6H12O6 Classification of Matter: Pure Substances Methanol CH4O Hexane C6H14 Caffeine C8N4O2H10 Pure Substances: Atoms • Atoms are the most basic building blocks of all matter. − There are 110+ different kinds of atoms o All 110+ atoms look identical and are composed of the same types of pieces called, subatomic particles o However, an atom is mostly empty • There are 3 subatomic particles and they differ in their location in the atom, their electrical charge and in their mass Pure Substances: Atoms − In the center of the atom is an extremely dense core called the nucleus, which is composed of protons and neutrons o Protons are electrically positive, and make up half of the mass of the atom o Neutrons are electrically neutral, and make up the other half of the mass of the atom − Surrounding the nucleus is an electrically negative “particle” called an electron o We tend to visualize the space the electrons occupy as a negatively charged cloud Classification of Matter: Pure Substances − An element is a pure substance made up of only one type of atom − Atoms can combine permanently together to make up molecules o A molecule is the smallest version of chemically combined atoms − Atoms combine to make up molecules, atoms and/or molecules can combine to make up mixtures Classification of Matter: Mixtures • Matter that isn’t pure must be a mixture of pure substances − The components in a mixture are simply blended together physically, which means they can be separated physically − When pure substances are blended together the components have the same properties as when they are separate o Melting point, boiling point, density, resistance to chemical change, etc. Your Turn… • Classify each of the following as a mixture or a pure substance Water Blood Table salt Iron Brass Uranium Wine Leather Pure substance Mixture Pure substance Pure substance Mixture Pure substance Mixture Mixture Classification of Matter: Mixtures − There are 2 types of mixtures: o Heterogeneous mixtures and o Homogeneous mixtures Mixtures: Homogeneous Mixtures • Homogeneous mixtures are uniform in composition − They have the same proportion of components throughout − This type of mixture is only composed of a single phase o Liquid, solid, gaseous, etc. − AKA solutions o For example salt water, brass, air, etc. o Particle size at the ion, or molecule level, .1 – 2 nm. Mixtures: Heterogeneous Mixtures • Heterogeneous mixtures are not uniform − Often have more than one phase o gas and liquid, gas and solid, solid and liquid. . . o e.g. Sea water, granite, blood, sand Two categories: ①A heterogeneous mixture of large (visible) solid particles in a liquid is called a Suspension o e.g. jar of muddy water, paint, dust particles in air. o Will settle over time. o Particle size greater than 1000 nm Mixtures: Heterogeneous Mixtures ②A mixture of smaller particles that don’t settle out, but are still visible is called a Colloid o e.g. Milk, smoke, fog o 2-1000 nm Your Turn… • Classify each of the following as a homogeneous or heterogeneous Soil The atmosphere A carbonated soft drink Gasoline Gold A solution of ethanol and water heterogeneous heterogeneous heterogeneous homogeneous homogeneous homogeneous Mixtures: Separation Techniques • All mixtures can be separated by some kind of physical method − Mixtures can be separated using several techniques which have been developed based on the type of mixture o o o o Filtration Distillation Chromatography Crystallization Separation Techniques: Chromatography • Chromatography is a technique that works for separating dissolved solids or a mixture of several liquids or even gaseous mixtures − Chromatography makes use of 2 phases to separate the mixture o Stationary phase – the phase the mixture is drawn across, it attracts each component in the mobile phase differently o Mobile phase – this phase contains the mix-ture to be separated; each component flows across the stationary phase at a unique rate Separation Techniques: Distillation • Distillation is an effective method of separating a mixture of liquids or to purify a liquid with solid particles dissolved in it − Uses the differences in the boiling points of different components in the mixture − Each component boils at a different temperature, therefore it is possible to boil off one liquid phase of the mixture at a time. • Distillation is used to purify alcohol, or water, or refine oil Separation Techniques: Crystallization • Crystallization is a separation technique, that produces a pure solid from a solidliquid solution − Usually involves a supersaturated solution o Rock candy, stalactite and mineral formation, crystallized honey, etc. Properties & Changes: Physical • A physical property is a characteristic that can be observed or measured without changing the identity of the substance − temperature, density, texture, color, shape, taste, specific heat, strength, luster, hardness, mass, odor, state, solubility, conductivity, ductility, malleability, etc. − It generally takes several phys properties to identify a substance Properties & Changes: Physical • There are 2 types of physical properties: − Intensive properties, which are properties that do not depend on the amount of the matter present. o Color o Odor o Luster o Malleable o Ductile o Conductive o Hardness o Melting Point o Boiling Point o Density Properties & Changes: Physical − Extensive properties, which are properties that do depend on the amount of matter present. o Mass o Volume o Area o Energy o Electrical Charge o Momentum Properties & Changes: Physical Changes • A change in a substance that does not include a change in the identity of a substance is a physical change − Grinding, melting, cutting, boiling, etc. • Melting and boiling are part of an important class of phys changes called changes of state − Change from one state of matter to another (solid to liquid) Properties & Changes: Chemical Changes • A property that relates to a substance’s ability to undergo changes that transform it into different substances is known as a chemical property − Easier to see when substances react to form new substances. e.g. the ability of charcoal to burn, ability of iron to rust, ability of silver to tarnish • A change in which 1 or more substances are converted into different substances is called a chemical change or chemical reaction (rxn) Properties & Changes: Chemical Changes • The substances that react in any chemical rxn are called reactants − They are the ingredients • The results of the reaction are called products • An example of a chemical rxn would be charcoal burning − Carbon and oxygen would be the reactants − Carbon dioxide and water are the products Physical vs. Chemical Properties PHYSICAL PROPERTIES CHEMICAL PROPERTIES A characteristic of a substance that can be observed or measured without changing composition. Ex: density, color, shape, hardness, melting & boiling points 2 kinds of phys properties; Intensive and extensive The ability of a substance to undergo chem rxns and to form new substances Ability to burn, to react, to decompose, etc. Your Turn… • Classify each of the following as physical or chemical changes P C Moth balls gradually vaporize in a closet Hydrofluoric acid attacks glass, and is used to etch calibration marks on glass utensils C A French chef making a sauce with brandy is able to burn off the alcohol from the brandy, leaving just the brandy flavoring C Chemistry majors sometimes get holes in the cotton jeans they wear to lab because of acid spills Properties & Changes: Energy • When physical or chemical changes occur, energy is always involved − Energy is the capacity to do work • Energy can be released or absorbed − It is transformed from one type to another, o Chemical energy stored in charcoal is converted into heat energy when ignited • Both energy and matter are conserved − They can neither be created nor destroyed − These are called the Laws of Conservation of Matter & Energy Properties & Changes: Energy • We will deal more with energy later, but there are 8 different types − Kinetic Energy − Potential Energy − *Light Energy − Sound Energy − Electrical Energy − *Chemical Energy − *Heat Energy − Mechanical Energy Pure Substances: Atoms • The only obvious difference between one type of atom and another are how many electrons, protons, and neutrons the different types of atoms have Pure Substances: Elements • Clusters of the same type of atoms are called elements − elements are pure substances that can’t be decomposed − Each element has features that make it unique and cause it to behave in a predictable manner − They are collectively organized in a huge chart called the periodic table (PT) Pure Substances: Elements • Each square on most Periodic Tables gives information about the element that the square represents. − − − − Atomic Number Atomic Symbol Atomic Name Atomic Weight Sec 1-3 Pg 20-24 Pure Substances: Elements − Atomic Number o This number is the order that the atom is on the Periodic Table o It also represents the number of protons that the atom has in its nucleus − Atomic Symbol o This is the symbolic representation of the element o This symbol is used when writing chemical formulas Pure Substances: Elements − Atomic Name o This is the name of the element, which may be named from mythology, latin, scientist of discovery, country of discovery, etc. − Atomic Weight o This is a measure of the mass of the average atom of that element o It’s equal to the mass of the nucleus of the average atom of that element Your Turn… • Use the clue provided to identify the element Atomic number: 5 Symbol: Ga Atomic weight: 12.011 Symbol: Pb Atomic weight: 210 Atomic number: 84 Boron Gallium Carbon Lead Astatine Polonium Pure Substances: Organization of the PT • The PT is organized into vertical columns called groups or families. − There are 18 columns • Each group contains elements with similar chemical characteristics − for instance elements in group 2 are reactive metals with similar abilities to bond to other kinds of atoms − Or group 18 which are all gases that are extremely resistant to chemical change Pure Substances: Organization of the PT • The horizontal rows of elements in the PT are called periods. − Physical and chem characteristics change predictably across the period − Elements close to each other tend to have similar characteristics, while elements farther apart become increasingly different o For example the elements on the far left of the PT tend to be soft, shiny solids that are good conductors o The far right are gases Pure Substances: Organization of the PT • The two sets of elements below the PT make up what are called the lanthanide and actinide series. − They are metallic and radioactive and should be placed after elements 57 & 89 Pure Substances: Organization of the PT • There is another major division of the elements, metals, nonmetals & metalloids. Pure Substances: Organization of the PT • A metal is a shiny element that is a good conductor of heat and electricity − At room temp, most metals are solids. o Mercury is an exception, it’s standard state is liquid (standard state is the state of matter at 25 C and 1 atm) − Most metals are also malleable o That is they can be hammered or rolled into thin sheets Pure Substances: Organization of the PT − Metals tend to be ductile. o Which means they can be drawn into a fine wire − Metals behave this way because of their high tensile strength o Tensile strength deals with its resistance to breaking. o The metal atoms just realign themselves as the metal is being stretched or hammered. Pure Substances: Organization of the PT • Nonmetals are elements that are poor conductors of heat and electricity − Many nonmetals are gases at room temperature (H, O, N, F, Cl) − One nonmetal is a liquid (Br) − The rest tend to be brittle solids (C, S, P, Se, I). Pure Substances: Organization of the PT • Metalloids are elements that have some of the characteristics of metals and some of nonmetals − on the stair step line that separates the metals from the nonmetals − All metalloids are solids at room temp − Tend to be less malleable than metals, but not as brittle as nonmetals − Metalloids tend to be semiconductive Pure Substances: Organization of the PT • The elements in the far right column are the noble gases − They are unique in that they are generally unreactive − All are gases at room temp − Ne, Ar, Kr, and Xe are all used in lighting − Helium is used in party balloons and weather balloons