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Chapter 3 Matter – anything that has mass and takes up space Everything around us Mass: measurement that reflects the amount of matter (usually in grams) Volume: the amount of space something takes up Chemistry – the study of matter and the changes it undergoes Solids particles vibrate but can’t move around fixed shape fixed volume incompressible Liquids particles can move around but are still close together variable shape fixed volume Virtually incompressible Gases particles can separate and move throughout container variable shape variable volume Easily compressed Vapor = gaseous state of a substance that is a liquid or solid at room temperature Plasma atoms collide with enough energy to break into charged particles (+/-) gas-like, variable shape & volume stars, fluorescent light bulbs, TV tubes II. Properties & Changes in Matter (p.73-79) Extensive vs. Intensive Physical vs. Chemical Physical Property can be observed & measured without changing the identity of the substance Physical properties can be described as one of 2 types: Extensive Property depends on the amount of matter present (example: length, mass, volume) Intensive Property depends on the identity of substance, not the amount (example: scent, density, melting point) Derived units = Combination of base units Volume (m3 or cm3 or mL) length length length Or measured using a graduated cylinder Density (kg/m3 or g/cm3 or g/mL) mass per volume 1 cm3 = 1 mL 1 dm3 = 1 L M D= V Chemical Property describes the ability of a substance to be observed reacting with or changing into another substance Examples: melting point physical flammable chemical density physical magnetic physical tarnishes in air chemical Physical Change changes the form of a substance without changing its identity properties remain the same Examples: cutting a sheet of paper, breaking a crystal, all phase changes Evaporation = Liquid -> Gas Condensation = Gas -> Liquid Melting = Solid -> Liquid Freezing = Liquid -> Solid Sublimation = Solid -> Gas Temperature vs. Time Q = mol x ΔHvapor Liquid & gas Gas Only Temp, oC Q = mol x ΔHfusion Solid & liquid Solid only, Q = m ΔT Cpsolid Time, min Liquid only Q= m ΔT Cpliquid Process that involves one or more substances changing into a new substance Commonly referred to as a chemical reaction New substances have different compositions and properties from original substances Reaction involves reactants reacting to produce products Signs of a Chemical Change change in color or odor formation of a gas (bubbles) formation of a precipitate (solid) change in light or heat Examples: rusting iron chemical dissolving in water physical burning a log chemical melting ice physical grinding spices physical Exothermic- heat energy EXITS the system surroundings usually feel warmer 1 g H2O (g) 1 g H2O (l) + 2260 J ex. Combustion, evaporation of water Endothermic- heat energy ENTERS the system - heat absorbed from surroundings - surroundings usually feel cooler - 1 g H2O (s) + 333 J 1 g H2O (l) - 1 g H2O (l) + 2260 J 1 g H2O (g) - ex. Cold packs, melting ice Although chemical changes occur, mass is neither created nor destroyed in a chemical reaction Mass of reactants equals mass of products massreactants = massproducts A+BC III. Classification of Matter (pp. 80-87) Matter Flowchart Pure Substances Mixtures MATTER yes Can it be physically separated? MIXTURE yes Is the composition uniform? Homogeneous Mixture (solution) no PURE SUBSTANCE no Heterogeneous Mixture yes Can it be chemically decomposed? Compound no Element Examples: graphite element pepper hetero. mixture sugar (sucrose) compound paint hetero. mixture soda solution Element composed of one type of identical atoms EX: copper wire, aluminum foil Compound composed of 2 or more elements in a fixed ratio (bonded together) properties differ from those of individual elements EX: table salt (NaCl) Variable combination of 2 or more pure substances, each retains its chemical identity & properties. Heterogeneous Homogeneous Homogeneous: are uniform throughout Solutions very small particles particles don’t settle EX: rubbing alcohol, gasoline, soda Heterogeneous medium-sized to large-sized particles particles may or may not settle EX: milk, freshsqueezed lemonade Examples: Answers: tea Solution muddy water Heterogeneous fog Heterogeneous saltwater Solution Italian salad dressing Heterogeneous 1. Metals: usually solid, good conductors of heat/electricity, malleable, and ductile 2. Nonmetals: solid, liquid or gas, brittle, poor conductors 3. Metalloids: transition between metals and nonmetals, semiconductors Atom: Composed of protons, electrons, and neutrons Smallest particle of matter that can be identified as one element Molecules: A collection of atoms chemically bonded together May be element or compound Electron: Negative charge Used in bonding (very mobile) Proton: Positive charge Located in nucleus Determine identity of atom Neutron Neutral (no charge) Helps determine mass of the atom Located in nucleus + Separation Methods Ways to separate mixtures – Chapter 3: Matter & Its Properties + Separating Mixtures Substances in a mixture are physically combined, so processes bases on differences in physical properties are used to separate component Numerous techniques have been developed to separate mixtures to study components Visually Magnetism Filtration Distillation Crystallization Chromatography + Filtration Used to separate heterogeneous mixtures composed of solids and liquids Uses a porous barrier to separate the solid from the liquid Liquid passes through leaving the solid in the filter paper + Distillation Used to separate homogeneous mixtures Based on differences in boiling points of substances involved + Crystallization Separation technique that results in the formation of pure solid particles from a solution containing the dissolved substance As one substance evaporates, the dissolved substance comes out of solution and collects as crystals Produces highly pure solids Rocky candy is an example of this + Chromatography Separates components of a mixture based on ability of each component to be drawn across the surface of another material Mixture is usually liquid and is usually drawn across chromatography paper Separation occurs because various components travel at different rates Components with strongest attraction for paper travel the slowest