Chemistry Fall 2009 Test 3 – Chapter 3 Matter – Properties and Changes

Chemistry Fall 2009 Test 3 - Chapter 3 Matter – Properties and Changes

Section 1: Properties of Matter Everything around you is matter. Matter that has a uniform and unchanging composition is called a substance, or pure substance. Examples of pure substances: table salt, and distilled water. Is seawater a substance? Every substance has its own unique set of physical and chemical properties. Observations of properties may depend on the conditions of the immediate environment. (Temperature and Pressure)

Physical Properties characteristics that can be measured or observed without changing the sample’s composition. Examples: shape, color, or weight. Can be used to describe substances – density, color, odor, taste, hardness, melting point, and boiling point provide an identifying characteristic of a substance.

Two types of Physical Properties: Extensive – dependent on the amount of substance present Mass, length, or volume Intensive – independent of the amount of substance present Density

Chemical Properties the ability or inability of a substance to combine with or change into one or more other substances Usually not obvious until the substance has changed or not changed composition as a result of: Contact with another substance The application of thermal energy The application of electrical energy Example: the ability of iron to rust when combined with air, but not when combined with nitrogen gas.

States of Matter 3 common physical forms – solid, liquid, and gas 4th state is plasma – it is a gas-like mixture of charged particles found in stars, and lightening bolts.

Solid form of matter that has a definite shape and a definite volume Examples: wood, iron, paper, and sugar Particles are very tightly packed, incompressible Not dependent on rigidity or hardness Expands slightly when heated

Liquid form of matter that flows, has a definite volume, but takes the shape of its container Examples: water, blood, and mercury Particles are not held rigidly in place and are less closely packed than the particles in a solid. The particles are able to move past one another. Liquids are virtually incompressible. Expand when heated

Gas a form of matter that flows to conform to the shape and volume of its container Examples: neon, methane, and air Particles are very far apart, easily compressed The words gas and vapor do not mean the same thing. Gas – refers to a substance that is in the gaseous state at room temperature. Vapor – refers to a gaseous state of a substance that is a solid or liquid at room temperature. Example - steam

Assignment Textbook p.60 (1-3, 5) – Write the questions and answers on a sheet of loose-leaf paper to be turned in at the end of the chapter. Workbook p. 13-14

Section 2: Changes in Matter Two types of changes that matter can undergo: Physical Chemical

Physical Change a change that alters a substance without changing its composition. (Appearance may change, but identity remains the same.) Examples: crumpling a sheet of aluminum foil, cutting a sheet of paper, and breaking a crystal Verbs used to indicate physical changes: bend, grind, crumple, split, crush, and cut Changes in state/phase are also physical changes. (Appearance changes, but identity remains the same.) Ex. Ice to water to steam – all are H2O Verbs indicating a change in phase: boil, freeze, condense, vaporize, or melt

Chemical Change the process that involves one or more substances changing into new substances (AKA chemical reaction) The new substances formed have different compositions and properties from the previous substances. Examples: the fermentation of grape juice, sugars, etc to wine; iron and oxygen forming rust In chemical reactions, the starting substances are called reactants and the newly formed substances are called products. Verbs referring to chemical reactions (rxns): explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot

Law of Conservation of Mass (LCM) states that mass is neither created nor destroyed during a chemical rxn –it is conserved. (Antoine Lavoisier – late 18th century) Massreactants Massproducts Example: Mercury (II) oxide yields mercury oxygen 216 g 200g 16g Mass of reactant mass of

Assignment: In your notes – complete practice problems 6-9 on p. 65. On your loose-leaf paper for the chapter, write and answer questions 10-12, 14 on p.65. Workbook p.15

Section 3: Mixtures in Matter A mixture is a combination of two or more pure substances in which each pure substance retains its individual properties. The composition of mixtures is variable. Most everyday examples of matter occur as mixtures. Examples – sodas, salad, sugar water, air, vinegar, steel, etc.

Types of Mixtures Heterogeneous – one that does not blend smoothly throughout and in which the individual substances remain distinct. Examples – sand and water, pizza, Italian salad dressing The existence of two or more unique areas indicates a heterogeneous mixture.

Homogeneous It is a mixture that has a constant composition throughout and it always has a single phase. Also referred to as solutions Examples – salt water, steel, cough medicine An alloy is a homogeneous mixture of metals, or a metal and a nonmetal in which metal is the primary component.

Separating Mixtures Most matter exists naturally as mixtures. Because mixtures are physically combined, we must use physical processes to separate them. These processes are based on the differences in physical properties of the substances in the mixture. Examples – magnetism, filtration, distillation, crystallization,

Filtration A technique that uses a porous barrier to separate a heterogeneous mixture of a solid and a liquid. Examples – filter paper, a colander, or a strainer

Distillation A separation technique that uses the differences in boiling points of the substances involved in a homogeneous mixture. A mixture is heated until the substance with the lowest boiling point boils to a vapor that can then be condensed into a liquid and collected. When precisely controlled, distillation can separate substances having boiling points that differ by only a few degrees.

Crystallization A separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance. It produces highly pure substances. Examples – Rock Candy

Chromatography A technique that separates the components of a mixture (called the mobile phase) on the basis of the tendency of each to travel or be drawn across the surface of another material (called the stationary phase).

MiniLab p.68 – Separating Ink Dyes With a partner, complete the miniLab on p.68. On a sheet of loose-leaf paper, copy the title, materials, procedures, and analysis sections. Answer the analysis questions and turn in your lab for credit.

Assignment: On your loose-leaf sheet for the chapter, write and answer questions 15-19 on p.69. Workbook p.16

Section 4: Elements and Compounds The classification of pure substances – two categories: elements compounds

Elements – a pure substance that cannot be separated into simpler substances b physical or chemical means; the basic building block of matter 91 elements occur naturally on Earth each has a unique name and symbol symbols – one, two, or three letters; the 1st letter is always capitalized and the remaining letter(s) are always lowercase Ex. Copper, Oxygen, Gold

Periodic Table organizes elements into a grid of horizontal rows called periods and vertical columns called groups or families. Elements in the same group have similar properties.

Compounds a combination of two or more different elements that are combined chemically. Ex. Water, table salt, table sugar, aspirin Approximately 10 million known compounds with new ones being discovered/developed at a rate of about 100,000 per year Formulas are written using the chemical symbols for the elements within the compound. Can be separated by chemical means

Compounds continued Properties are different from those of its component elements Ex – Hydrogen – tasteless, odorless gas Oxygen - tasteless, odorless gas Water – clear liquid at room temp. Ex – Sodium – highly reactive metal that fizzes and burn in water Chlorine – poisonous, pale green gas Sodium Chloride – white, unreactive solid that we use to flavor foods (SALT)

Law of Definite Proportions – states that, regardless of amount, a compound is always composed of the same elements in the same proportion by mass. This law is used to find the formulas for compounds.

Percent by Mass – (mass of element / mass of compound) x 100 Complete practice problems 20-24 on page 76 in your notes.

Assignment: On your loose-leaf page for the chapter, write and answer questions 25-30 on p.77. Workbook p.17-18 Review the Study Guide Summary on p.81. Make sure that you have all equations and vocabulary terms in your notes. A study guide for this chapter has been placed on the class website.

About the test The test will be Thursday, September3, 2009. It will consist of 35 multiple-choice questions, and 4 problems.

Law of Multiple Proportions – states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ration of small whole numbers.