Zumdahl • Zumdahl • DeCoste World of CHEMISTRY

Chapter 2 Matter

2.1 The Particualte Nature of Matter Objective: To Learn about the composition of matter. Copyright © by Houghton Mifflin Company

Matter, the “stuff” the universe is made of. Two Characteristics: Mass Occupies Space Examples Copyright © by Houghton Mifflin Company

The Atomic Nature of Matter All matter consists of tiny particles called ATOMS. Consider a painting by George Seurat: Copyright © by Houghton Mifflin Company

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Although objects in the macroscopic world appear continuous and uniform, they are really particulate in nature, i.e. they are composed of atoms. Copyright © by Houghton Mifflin Company

2.2 Elements and Compounds Objectives: To Learn the difference between elements and compounds. Copyright © by Houghton Mifflin Company

All Atoms Are Not Equal All matter is composed of about 100 different atoms. Example – the air we breath is composed of: 80% Nitrogen (N2) and approx. 20% Oxygen (O2). Words in a book are composed of different arrangements of our 26 letter alphabet. Copyright © by Houghton Mifflin Company

Compounds Compounds are substances made by bonding atoms together in specific ways. They are composed of different atoms, configured (arranged) in the same way. Example: H2O - Water Contains 2 Hydrogen atoms (H2) and 1 Oxygen atom (O). O H H CO2 another compound (dry ice) composed of molecules of O=C=O Copyright © by Houghton Mifflin Company

Molecules Molecules are made up of atoms that are ‘stuck’ together. A glass of water contains lots of molecules that are closely stuck together. Steel is composed of iron (Fe) Carbon (C) and various other atoms depending on how it will be used (e.g. Chromium (Cr) and Nickel(Ni) are used for stainless steel). Copyright © by Houghton Mifflin Company

Atom Combinations Copyright © by Houghton Mifflin Company

Elements Elements are substances that contain only one type of atom. A sample of Lead (Pb) contains may atoms but they are all the same. Some pure elements do contain molecules: e.g. Hydrogen H H (H2) A Compound always contains different atoms. Copyright © by Houghton Mifflin Company

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Figure 2.5: The three forms of the element carbon: Diamond. Copyright © by Houghton Mifflin Company

Figure 2.5: The three forms of the element carbon: Graphite. Copyright © by Houghton Mifflin Company

Figure 2.5: The three forms of the element carbon: Buckminsterfullerene. Copyright © by Houghton Mifflin Company

Objectives: To define the three states of matter. 2.3.The States of Matter Objectives: To define the three states of matter. Copyright © by Houghton Mifflin Company

3 States of Matter Solid Liquid Gas Each state of matter changes the properties of a molecule. Copyright © by Houghton Mifflin Company

Characteristics of the 3 States of Matter for Water Solid Less dense (ice floats) Increased strength (ice-skaters) Liquid Allows for diffusion Takes the shape of the container Gas Invisible to the naked eye

Solid Liquid Gas Rigid Fixed Shape and Volume Definite volume Takes the shape of the container Liquid No defined shape No fixed volume Gas

Focus Questions How do atoms, compounds, and elements differ? How do elements differ from compounds? (consider the letters in the word ‘chemistry’) Describe the differences between a solid, liquid and a gas. Copyright © by Houghton Mifflin Company

2.4 Physical and Chemical Properties of Change Objectives: To learn to distinguish between physical and chemical properties. To learn to distinguish between physical and chemical changes Copyright © by Houghton Mifflin Company

Physical Properties A Physical Property is a characteristic that we use to recognize a particular substance: Odor Color Volume State (liquid, solid or gas) Density Melting/boiling point Copyright © by Houghton Mifflin Company

Chemical Properties Chemical properties refer the ability of a pure substance to form new substances: Wood burning → Heat + CO2 (g) + Ashes (s) Copyright © by Houghton Mifflin Company

Example 2.1 Identifying Physical and Chemical Properties Physical or Chemical? Gallium Metal Melts in your hand. Platinum does not react with oxygen at room temperature. This page is blue. The copper sheets that form the “skin” of the Statue of Liberty have acquired a greenish coating over the years. Copyright © by Houghton Mifflin Company

Physical and Chemical Changes of Matter Solid Liquid Gas Melting Boiling Copyright © by Houghton Mifflin Company

Figure 2.7: The three states of water: Solid. Copyright © by Houghton Mifflin Company

Figure 2.7: The three states of water: Water. Copyright © by Houghton Mifflin Company

Figure 2.7: The three states of water: Gas. During all of these phase changes, the water molecule (H2O) stays bonded. The motions/distance of the individual molecules changes, i.e. the changes are “physical changes”. Copyright © by Houghton Mifflin Company

Figure 2.8: Electrolysis, the decomposition of water by an electric current, is a chemical process. Exposure to an electrical current produces a “chemical” change. 2H2O → 2H2 +O2 molecules Copyright © by Houghton Mifflin Company

Summarizing It All Physical Changes involve one or more physical properties change (Odor, Color, Volume, State (liquid, solid or gas),Density, and Melting/boiling point. Chemical changes involves a change in the components of the substance, i.e. a given substance changes (reacts) to create a different substance. Copyright © by Houghton Mifflin Company

Example 2.2 Self Check Chemical or Physical? 1. Milk Turns Sour. 2. Wax is melted over a flame and then catches fire and burns. Copyright © by Houghton Mifflin Company

2.5 Mixtures and Pure Substances Objectives: To learn to distinguish between mixtures and pure substances. Copyright © by Houghton Mifflin Company

Mixtures A Mixture can be defined as something that has variable composition. Copyright © by Houghton Mifflin Company

Figure 2.9: The composition of air. Copyright © by Houghton Mifflin Company

Chart examining each substance of air. The composition of mixtures varies; the atomic composition of compounds always remains the same.

Figure 2. 10: Twenty-four-karat gold is an element Figure 2.10: Twenty-four-karat gold is an element. Eighteen-karat gold is an alloy. Fourteen-karat gold is an alloy. Copyright © by Houghton Mifflin Company

Figure 2.11: Representation of H2O molecules. Compound or Mixture? Copyright © by Houghton Mifflin Company

Pure Substances A Pure Substance always has the same composition. i.e they are either elements or compounds. Mixtures can be separated into pure substances . Copyright © by Houghton Mifflin Company

Homogenous and Heterogenous Mixtures Homogenous Mixtures is the same throughout. It is also called a Solution. Example: Table salt mixed with water. The composition is equally distributed throughout the entire solution. Copyright © by Houghton Mifflin Company

Homogenous and Heterogeneous Mixtures A Heterogeneous mixture contains regions that have different properties from those of other regions. Example: sand and water Copyright © by Houghton Mifflin Company

Example 2.3 Self Check Classify each of the following as Pure, Homogeneous, or heterogeneous> Maple syrup The oxygen and helium in a scuba tank Oil and vinegar salad dressing Common salt (NaCl sodium chloride) Copyright © by Houghton Mifflin Company

2.6 Separations of Mixtures Objectives: To learn two methods of separating mixtures. Copyright © by Houghton Mifflin Company

Figure 2.14: The solution is boiled and steam is driven off. Distillation Liquid →Gas →Liquid Copyright © by Houghton Mifflin Company

Figure 2.14: Salt remains after all water is boiled off. Copyright © by Houghton Mifflin Company

Figure 2.15: No chemical change occurs when salt water is distilled. Copyright © by Houghton Mifflin Company

Figure 2.16: Filtration separates a liquid from a solid. Filtration separates heterogeneous Mixtures. Copyright © by Houghton Mifflin Company

Figure 2.17: Separation of a sand-saltwater mixture. Copyright © by Houghton Mifflin Company

Figure 2.18: The organization of matter. Copyright © by Houghton Mifflin Company

Setup to boil water. Copyright © by Houghton Mifflin Company

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