Matter – Properties and Changes Chapter 1 Matter – Properties and Changes

Properties of Matter Section 2

Definitions Mass – a measure of the amount of a substance Matter – anything that has mass and takes up space

Building blocks of matter Atoms – smallest unit of an element that maintains the identify of the element Element – a pure substance that cannot be broken down into simpler, stable substances; made of one type of atom

Building blocks of matter Compound – substance that can be broken down into simple stable substances; made of two or more elements that are chemically combined

Characteristic properties Property – characteristic that defines/classifies a group of substances; can be used to identify unknown substances

Characteristic properties Extensive properties – depend on the amount of matter present (volume, mass, amount of energy) Intensive properties – do NOT depend on the amount of matter present (melting point, boiling point, density, electrical conduction)

Physical Properties Characteristics that can be observed or measured without changing the sample’s composition Ex: density, color, odor, taste, hardness, melting point, boiling point NaCl Solid, white crystals @ RT, salty taste

Physical Changes Alter the substance WITHOUT changing the composition Terms: bend, grind, crumple, split, crush, phase changes (melt, boil, freeze, condense, vaporize)

States of Matter Solid Liquid Gas plasma

Solid Definite shape Incompressible Definite volume Tightly packed matter Expand when heated

Liquid Flows Incompressible Constant volume Expands when heated Takes shape of container Particle able to move past each other

Gas Easily compressed Particles are very far apart Fills entire volume of its container Flows to conform to container shape

Plasma High-temperature physical state of matter in which atoms lose most of their electrons

Chemical Properties Ability of substance to react or not react with another substance Ex: oxidizing (reacting with O2) Fe reacts with O2 to make Fe2O3; but does not react with N2

Properties of Cu Physical Properties Reddish brown, shiny Easily shaped into sheets (malleable) Easily drawn into wire (ductile) Good conductor of heat & electricity Density = 8.92 g/ml mp = 1085 °C bp = 2570 °C Chemical Properties Forms green copper carbonate compound when in contact with moist air Forms new substances when combined with nitric acid and sulfuric acid Forms a deep blue solution when in contact with ammonia

Chemical Changes Ability of substance to combine with or change into one or more substances New substances have different compositions and properties than original substances Terms: explode, rust, oxidize, corrode, tarnish, ferment, burn, rot

Chemical changes Also known as chemical reactions Substances that react are REACTANTS Substances that are formed are PRODUCTS

Law of conservation of energy Energy is always involved with changes, physical OR chemical Total amount of energy remains the same; energy is NOT created or destroyed Energy may take a different form

Vapor vs. Gas Vapor refers to a gaseous state of a substance that is solid or liquid at room temp Gas refers to a substance that is naturally at the gaseous state at room temp

Classify each of the following as physical or chemical property Fe and O form rust Chemical Fe is more dense than Al Physical Mg burns brightly when ignited Oil and water do not mix Hg melts at -39 °C

Law of Conservation of Mass Mass cannot be created nor destroyed during a chemical reaction – it is conserved Mass reactants = mass products

Mixtures 2 or more substances (compounds) are combined Retains individual chemical properties Most substances will mix Difficult to keep things pure

Types of Mixtures Homogeneous mixture Heterogeneous mixture uniform composition throughout Also called solutions Ex: salt water Heterogeneous mixture Does not blend well Individual substances remain distinct Ex: sand and water

Separating Mixtures Filtration Distillation Crystallization Uses a porous barrier separate solid and liquid Distillation Differences in boiling points of substance Crystallization Results in formation of pure solid particles contained in the dissolved substance Chromatography Separates mixture based on ability to be moved across surface

Pure substances Has a fixed composition Can be a compound or an element Are always homogenous But differ from mixtures by Every sample has exactly the same characteristic properties Every sample has the exact same composition

Elements & Compounds Section 1.3

Elements Pure substance Cannot be further separated 91 naturally occurring elements Ex: Cu, O, N, H Remainder are made in the lab Located on the Periodic Table Developed by Dmitri Mendeleev

Periodic table Organizes elements based on chemical properties Each box has the element symbol and its atomic number Some symbols are based on English names, others are based on Latin or German names

Periodic table Vertical columns are groups or families They are numbered 1 through 18 (left to right) Each group has elements with similar chemical properties Two major categories are metals and nonmetals Metalloids have intermediate properties

Periodic table Horizontal rows are periods Physical and chemical properties change across a period Elements close together have more similar properties than those that are far apart

Periodic table Two sets of elements below the table are the lanthanide and actinide series that fit just after elements 57 and 89 Placed below to prevent the table from being too wide

Periodic table: metals On the left and in the center Have metallic luster (shininess) Conduct electricity Most are solids at room temperature They are malleable (rolled into sheets) They are ductile (drawn into wire) High tensile strength (resist breakage)

Periodic table: nonmetals Many are gases at room temperature, one is liquid, some are solids They are brittle not ductile or malleable Low conductivity of heat / electricity

Periodic table: noble gases Group 18 Generally unreactive

Periodic table: metalloids Located between metals and nonmetals Share some characteristics with metals and some with nonmetals All are solids at room temperature Less malleable than metals and not as brittle as nonmetals; some have luster Some are semiconductors of electricity

Compounds Combine 2 or more elements Ex: water, table salt, table sugar, aspirin Can be broken down into elements with heat/electricity

Law of Definite Proportions Regardless of the amount, a compound is always made of the same elements in the same proportions by mass Ex: table sugar = C, H, O Refer to p. 75 Tables 3-4 and 3-5

Law of Multiple Proportions When different compounds are formed by a combination of the same elements, they combine in whole # ratios Ex: Cu compounds on p. 76 Table 3-6