Chapter 2

Matter Matter Matter – anything that has mass and takes up space Mass Mass – measure of the amount of matter that an object contains Volume Volume – measure of the space occupied by the object

Extensive & Intensive Properties properties. What you observe when you examine a sample of matter is its properties. 1.Extensive Property amount of matter 1.Extensive Property – a property that depends on the amount of matter in a sample Ex. Mass, volume, weight, length 2.Intensive Property type of matter 2.Intensive Property – a property that depends on the type of matter in a sample (prefix–in means within) Ex. Hardness, color, odor, luster, conductivity, malleability, ductility, freezing point, boiling point, melting point, density

Substances Substance Substance – Matter that has a uniform and definite composition Either an element or a compound Also called pure substance Rarely found in nature Fixed proportions to each other Examples Examples  Diamond  Water  Gold  Copper  Sugar  Nitrogen

Mixtures Mixture Mixture – a physical blend of two or more substances that are not chemically combined Do not exist in fixed proportions to each other Most natural substances are mixtures Can usually be separated back into its original components Examples Examples  Concrete  Soil  Salt water  Milk  Coke  Gasoline  Fruit salad  Atmosphere Examples Examples  Concrete  Soil  Salt water  Milk  Coke  Gasoline  Fruit salad  Atmosphere

Two Types of Mixtures Homogeneous Mixture (solution) Homogeneous Mixture (solution) – a mixture in which the composition is uniform throughout. Consists of a single phase Can’t see them separately or separate them physically Examples  stainless steel  air  olive oil  vinegar

Two Types of Mixtures Heterogeneous Mixture Heterogeneous Mixture – a mixture in which the composition is not uniform throughout. Consists of a two or more phases Examples  chicken soup  oil & vinegar mixed  milk  rice crispy treats

Separating Mixtures Differences in physical properties can be used to separate mixtures Examples  coffee filters  draining pasta Filtration Filtration – process that separates a solid from a liquid

Separating MixturesExample  separating water from other substances in the water Distillation Distillation – process of boiling a liquid to produce a vapor and then condensing the vapor into a liquid

States of Matter 1. Solid 2. Liquid 3. Gas

States of Matter Solid Definite shape Definite volume Not easily compressed Characteristics Does not take the shape of the container Particles packed tightly together, and often in orderly arrangement Almost incompressible Expands only slightly when heated

States of Matter Liquid Indefinite shape Definite volume Not easily compressed Characteristics Take the shape of the container in which it is placed Particles in close contact, but arrangement of particles is not orderly (can flow past each other) Almost incompressible Expands slightly when heated

States of Matter Gas Indefinite shape indefinite volume Easily compressed Characteristics Take the shape of the container in which it is placed Can expand to fill any volume Particles are much farther apart Easily compressed into a smaller volume

Physical Change Some properties of a material change, but the composition of the material does not change Examples Examples  Changes of state  Changes of state such as boiling water, condensation (boil, freeze, melt, condense)  Physical deformation  Physical deformation such as cutting, denting, stretching, breaking, crushing

Chemical Change Examples  Silver spoon tarnishes  Metal rusts  Methane burns  Methane burns  Sugar ferments  Burn, rot, rust, decompose, ferment, explode, corrode usually mean a chemical change Chemical Change A change that produces matter with a different composition than the original matter

Elements Element Element – simplest form of matter that has a unique set of properties. cannotcannot be broken down into simpler substances Examples  Hydrogen  Nitrogen  Oxygen

Compounds Compound Compound – substance that contains two or more elements chemically combined in a fixed proportion. Compounds can be broken down into simpler substances by chemical means Examples  Sugar (C 12 H 22 O 11 )  Salt (NaCl)  Water (H 2 O)

Breaking Down Compounds A chemical change is required to breakdown compounds into simpler substances Some methods Heating Sugar heat Carbon + Water compound element element Electric current Water electricity Hydrogen + Oxygen compound element element

Properties of Compounds In general, properties of compounds are quite different from those of their component elements. Example Compound ---- Table Salt (NaCl) Element ---- Sodium (Na) – soft, gray metal Element ---- Chlorine (Cl) – pale yellow-green poisonous gas.

Element Simplest formCompound Substance Definite composition HomogeneousMixture Uniform; also called a solutionHeterogeneousMixture Nonuniform; Distinct phases Mixture Variable composition Matter Can be separated physically Can be separated chemically SilverSaltStainless Steel Cement Classifying Matter Any sample of matter is either an element, a compound, or a mixture

Chemical Symbols Each element on the periodic table is represented by a one or two letter chemical symbol. Examples Na – SodiumAu - Gold C - Carbon K - Potassium The first letter of a chemical symbol is always capitalized. When a second letter is used, it is lowercase

Symbols Derived From Latin SodiumNa PotassiumK AntimonySb CopperCu GoldAu SilverAg IronFe LeadPb TinSn

Physical Properties Physical Property observed or measured Physical Property – a quality or condition of a substance that can be observed or measured without changing the substance’s composition Examples Examples  Appearance  Density  Texture  Malleability  Color  Boiling Point  Odor  Melting Point  Conductivity  Hardness

Chemical PropertyExamples Gasoline -- burns in air Iron -- rusts Baking Soda -- reacts with vinegar Copper -- rusts in water Table salt -- does not react with vinegar Chemical Property Ability of a substance to undergo a specific chemical change Chemical properties can be observed only when a substance undergoes a chemical change.

Recognizing Chemical ChangesExamples Gasoline -- burns in air Iron -- rusts Baking Soda -- reacts with vinegar Copper -- rusts in water Table salt -- does not react with vinegar Words such as burn, rot, rust, decompose, ferment, explode, and corrode usually signify a chemical change. During a chemical change, the composition of matter always changes.

Recognizing Chemical Changes Precipitate – Precipitate – solid that forms and settles out of a liquid mixture Ex. Ex. – ring of soap scum in your bathtub Possible Clues Transfer of energy A change in color The production of gas The formation of a precipitate The only way to be sure a chemical change has occurred is to test the composition of a sample before and after the change

Law of Conservation of Mass During any chemical reaction, the mass of the products is always equal to the mass of the reactants. Example 2H 2 + O 2 2H 2 0 2g 2g = 4g reactants = product