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)

C. Density – a physical property  Derived units = Combination of base units  Volume (m 3 or cm 3 or mL)  length  length  length  Or measured using a graduated cylinder D = MVMV 1 cm 3 = 1 mL 1 dm 3 = 1 L  Density (kg/m 3 or g/cm 3 or g/mL)  mass per volume

 Chemical Property  describes the ability of a substance to be observed reacting with or changing into another substance

 Examples:  melting point  flammable  density  magnetic  tarnishes in air physical chemical physical 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 =  Condensation =  Melting =  Freezing =  Sublimation = Liquid -> Gas Gas -> Liquid Solid -> Liquid Liquid -> Solid Solid -> Gas

Temp, o C Solid only, Q = m ΔT C psolid Q = mol x ΔH fusion Solid & liquid Liquid only Q= m ΔT C pliquid Q = mol x ΔH vapor Liquid & gas Time, min Temperature vs. Time Gas Only

 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  dissolving in water  burning a log  melting ice  grinding spices chemical physical chemical physical

Exothermic- heat energy EXITS the system  surroundings usually feel warmer  1 g H 2 O (g)  1 g H 2 O (l) J  ex. Combustion, evaporation of water

Endothermic- heat energy ENTERS the system - heat absorbed from surroundings - surroundings usually feel cooler - 1 g H 2 O (s) J  1 g H 2 O (l) - 1 g H 2 O (l) J  1 g H 2 O (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 mass reactants = mass products A + B  C

III. Classification of Matter (pp ) Matter Flowchart Pure Substances Mixtures

MATTER Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous MixtureCompoundElement MIXTUREPURE SUBSTANCE yes no Can it be chemically decomposed? noyes Is the composition uniform? noyes

 Examples:  graphite  pepper  sugar (sucrose)  paint  soda element hetero. mixture compound hetero. mixture 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. HeterogeneousHomogeneous

 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, fresh- squeezed lemonade

 Examples:  tea  muddy water  fog  saltwater  Italian salad dressing  Answers:  Solution  Heterogeneous  Solution  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