Matter and ChangeMatter and ChangeChapter 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 Matter2.1 Properties of MatterDescribing 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 Assessment2.1 Section AssessmentPage 421 - 8

2.2 Mixtures2.2 MixturesClassifying 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 ProcessDistillation Process

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

Substance v. Mixtures1. Sodium2. Water3. Soil4. Coffee5. Oxygen6. Alcohol7. Carbon dioxide8. Cake batter9. Nail polish

10. Air11. Soup12. Iron13. Salt water14. Ice cream15. Nitrogen16. Eggs17. Blood18. Table salt

Homogeneous v. Heterogeneous1. Flat soda pop2. Cherry vanilla

ice cream3. Salad dressing4. Sugar5. Soil6. Aluminum foil7. Black coffee8. Sugar water

9. City air10. Paint11. Alcohol12. Iron13. Beach sand14. Pure air15. Spaghetti

sauce.

Separation of Mixtures1. Sand and water2. Sugar and water3. Oil and water4. Sand and gravel5. Mixture of heptane (boiling point

98°C) and heptanol (bp 176°C)6. Mixture of iodine solid and sodium

chloride (iodine not soluble in water)7. Mixture of lead and aluminum pellets8. Mixture of salt and iron filings.

2.2 Section Assessment2.2 Section AssessmentPage 46

◦Problems 9 – 10Page 47

◦Problems 11 - 17

2.3 Elements and CompoundsElement – 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 AssessmentPage 52Problems 20 – 27.

2.4 Chemical ReactionsChemical 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),

Physical v. chemical properties1. Red color2. Density3. Flammability4. Solubility5. Reacts with acid

to form hydrogen

6. Supports combustion

7. Bitter taste8. Melting point

9. Reacts with water to form a gas

10. Reacts with a base to form water

11. Hardness12. Boiling point13. Can neutralize a

base14. Luster15. Odor

Physical v. Chemical Change1. Sodium hydroxide dissolves in water2. Hydrochloric acid reacts with sodium

hydroxide to produce a salt, water and heat

3. A pellet of sodium is sliced in two4. Water is heated and changed to steam5. Potassium chlorate decomposes to

potassium chloride and oxygen gas.6. Iron rusts.7. Ice Melts8. Acid on limestone produces carbon

dioxide gas.9. Milk sours.10. 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 AssessmentPage 55Problems 28 - 34