Matter and Change

Matter and Change Chapter 2 Wilbraham, Antony C., Dennis D. Staley, Michael S. Matta, and Edward L. Waterman. Prentice Hall Chemistry. 1st ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2008.

2.1 Properties of Matter • Describing Matter • Properties used to describe matter can be classified as extensive or intensive • Extensive property – is a property that depends on the amount of matter in a sample. • Mass – a measure of the amount of matter the object contains • Volume – measure of the space occupied by the object • Intensive property – is a property that depends on the type of matter in a sample, not the amount. • Hardness, color, texture, etc.

Identifying Substances • Every sample of a given substance has identical intensive properties because every sample has the same composition. • Substance – Matter that has a uniform and definite composition. • Physical property – a quality or condition of a substance that can be observed or measured without changing the substance’s composition.

States of Matter • Three states of matter are solid, liquid, and gas. • Solid – a form of matter that has a definite shape and volume • Liquid – form of matter that has an indefinite shape, flows, yet has a fixed volume. • Gas – form of matter that takes both the shape and volume of its container.

Solid • Have definite shape and volume • Particles are packed close/tight together in a form held together by molecular forces. • Divided into two categories • Crystalline – orderly arrangement • Iron, ice, and diamond • Amorphous – no order • Rubber and wax

Liquid • Has a definite volume but no shape • Take shape of the container they occupy. • Particles are tightly packed together, but are able to slide pass each other • Particles move fast enough to overcome molecular forces

Gas • Are free to move in all directions • Gases expand to fill a space. • Particles move fast enough to break away from each other • Particles move rapidly

States of Matter Comparison Video

Physical Changes – some properties of a material change, but the composition of the material does not change. • Physical changes can be classified as reversible or irreversible. • Reversible - Boil, freeze, melt, condense, • Irreversible - break, split, grind, cut, and crush

Physical Properties describe Matter. • Color, shape, melting point, boiling point, density, strength, hardness, ability to conduct electricity, etc. • Melting point – temperature and pressure at which a solid becomes a liquid • Boiling point – temperature at which a liquid becomes a gas. • Density – ratio of the mass of a substance to the volume of a substance. D = M/V

2.1 Section Assessment • Page 42 • 1 - 8

2.2 Mixtures • Classifying Mixtures • Mixture is physical blend of two or more components. • Chicken noodle soup • Air • Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures.

Homogenous mixture (solution) – is a mixture in which the composition is uniform throughout. • Stainless steel – mixture of iron, chromium, & nickel. • Heterogeneous Mixtures • A mixture in which the composition is not uniform • Phase – used to describe any part of a sample with uniform composition and properties. • Italian dressing. – oil phase floats on top of the water phase.

Separating Mixtures • Differences in physical properties can be used to separate mixtures. • Filtration – separates a solid from the liquid in a heterogeneous mixture. • Water and sand • Distillation – liquid is boiled to produce a vapor that is then condensed into a liquid. (see Fig 2.8, pg 47).

Distillation Process Image from: http://www.rpdp.net/sciencetips_v3/images/p8a3/P8A3_clip_image012.jpg

Sodium Water Soil Coffee Oxygen Alcohol Carbon dioxide Cake batter Nail polish Air Soup Iron Salt water Ice cream Nitrogen Eggs Blood Table salt Substance v. Mixtures

Flat soda pop Cherry vanilla ice cream Salad dressing Sugar Soil Aluminum foil Black coffee Sugar water City air Paint Alcohol Iron Beach sand Pure air Spaghetti sauce. Homogeneous v. Heterogeneous

Separation of Mixtures • Sand and water • Sugar and water • Oil and water • Sand and gravel • Mixture of heptane (boiling point 98°C) and heptanol (bp 176°C) • Mixture of iodine solid and sodium chloride (iodine not soluble in water) • Mixture of lead and aluminum pellets • Mixture of salt and iron filings.

2.2 Section Assessment • Page 46 • Problems 9 – 10 • Page 47 • Problems 11 - 17

2.3 Elements and Compounds • Element – is the simplest form of matter that has a unique set of properties. • Oxygen (O2) Hydrogen (H2) • Compound – is a substance that contains two or more elements chemically combined in a fixed proportion. • Water (H2O) • Compounds can be broken down into simpler substance by chemical means, but elements cannot.

Breaking Down Compounds: • Physical methods that are used to separate mixtures cannot be used to break a compound into simpler substances. • Chemical change is a change that produces matter with a different composition than the orginal matter. • Sugar broken down into C and H2O(g) when heated. • Broken down into H2 and O2 by passing a current through

Properties of Compounds • Compounds and the elements from which they form have different properties. • Chlorine (Cl2) is a poisonous gas, while sodium (Na) is a extremely reactive solid, combined they form NaCl, table salt.

Distinguishing Substances and Mixtures • If the composition of a material is fixed, the material is a substance. • If the composition of a material may vary, the material is a mixture.

Can be separated chemically

Symbols and formulas • Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds. • Chemical symbol – each element is represented by one or a two letter symbol. 1st letter is always captialized.

Section 2.3 Assessment Page 52 Problems 20 – 27.

2.4 Chemical Reactions Chemical properties: burn, rot, rust, decompose, ferment, explode, and corrode, are used to describe a chemical change. Chemical property – is the ability of a substance to undergo a specific chemical change. During a chemical change, the composition of matter always changes.

Chemical reaction – is when one or more substance change into one or more new substances. A chemical reaction (rxn) has two parts the reactants and the products. Reactant – substance present at the start of the rxn Product – substance produced in the rxn. H2 + O2→ 2H2O

Recognizing Chemical Changes • Possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate. • Precipitate – is a solid that forms and settles out of a liquid mixture. • The only way to know for sure if a chemical change is to test the composition of the sample before and after the change. • pH, heat, bubbles (acid/base rxn),

Red color Density Flammability Solubility Reacts with acid to form hydrogen Supports combustion Bitter taste Melting point Reacts with water to form a gas Reacts with a base to form water Hardness Boiling point Can neutralize a base Luster Odor Physical v. chemical properties

Physical v. Chemical Change • Sodium hydroxide dissolves in water • Hydrochloric acid reacts with sodium hydroxide to produce a salt, water and heat • A pellet of sodium is sliced in two • Water is heated and changed to steam • Potassium chlorate decomposes to potassium chloride and oxygen gas. • Iron rusts. • Ice Melts • Acid on limestone produces carbon dioxide gas. • Milk sours. • Wood rots.

Conservation of Mass • During any chemical rxn, the mass of the products is always equal to the mass of the reactants. • Law of Conservation of Mass – states that in any physical change or chemical rxn, mass is conserved.

2.4 Section Assessment Page 55 Problems 28 - 34

Matter and Change