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Table of Contents

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  1. The Science of Chemistry Chapter 1 Table of Contents Section 1What Is Chemistry? Section 2Describing Matter Section 3How Is Matter Classified?

  2. Section1 What Is Chemistry? Chapter 1 Working with the Properties and Changes of Matter • A chemical is any substance that has a definite composition. • A chemical reaction is the process by which one or more substances change to produce one or more new substances.

  3. Visual Concepts Chapter 1 Chemical

  4. Section1 What Is Chemistry? Chapter 1 Physical States of Matter • The states of matter are the physical forms of matter which are solid, liquid, gas, and plasma. • Macroscopic refers to what you can see with the unaided eye. • Microscopicrefers to what you would see if you could see individual atoms.

  5. Section1 What Is Chemistry? Chapter 1 Physical States of Matter, continued Properties of the Physical States • Solids have a fixed volume and shape that result from the way their particles are arranged. • Liquidshave a fixed volume but not a fixed shape. • Gaseshave neither fixed volume nor shape.

  6. Chapter 1 Section1 What Is Chemistry? Water in Three States

  7. Visual Concepts Chapter 1 Solid, Liquid and Gas

  8. Section1 What Is Chemistry? Chapter 1 Changes of Matter • Physical changesare changes in which the identity of a substance doesn’t change. • Changes of state are physical changes. • Chemical changesoccur when the identities of substances change and new substances form.

  9. Chapter 1 Section1 What Is Chemistry? Changes of Matter, continued Chemical Changes • mercury(II) oxide mercury + oxygen • Reactants are the substances are the left-hand side of the arrow. • They are used up in the reaction. • Products are the substances are the right-hand side of the arrow. • They are made in the reaction.

  10. Evidence of a Chemical Change Chapter 1 Section1 What Is Chemistry?

  11. Section1 What Is Chemistry? Chapter 1 Changes of Matter, continued Evidence of a Chemical Change • Evidence that a chemical change may be happening generally falls into one of the following categories. • the evolution of a gas • the formation of a precipitate • the release or absorption of energy • a change in temperature or the giving off of light energy • a color change in the reaction system

  12. Visual Concepts Chapter 1 Chemical Reaction

  13. Section2 Describing Matter Chapter 1 Matter Has Mass and Volume • Matter is anything that has mass and volume. • Volume is the space an object occupies. • Mass is the quantity of matter in an object. • Devices used for measuring mass in a laboratory are called balances. • Weight is the force produced by gravity acting on a mass.

  14. Visual Concepts Chapter 1 Comparing Mass and Weight

  15. Section2 Describing Matter Chapter 1 Units of Measurement • When working with numbers, be careful to distinguish between aquantityand itsunit. • Quantity describes something that has magnitude, size, or amount. • Unit is a quantity adopted as a standard of measurement.

  16. Chapter 1 Section2 Describing Matter Units of Measurement, continued Scientist Express Measurements in SI Units • Scientists worldwide use a set of units called the Système Internationale d’Unités or SI.

  17. Chapter 1 Section2 Describing Matter Units of Measurement, continued Scientist Express Measurements in SI Units, continued • Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.

  18. Visual Concepts Chapter 1 SI (Système Internationale d’Unités )

  19. Visual Concepts Chapter 1 Conversion Factor

  20. Section2 Describing Matter Chapter 1 Unit of Measurement, continued Converting One Unit to Another • A conversion factor is a simple ratio that relates two units that express a measurement of the same quantity. • example: You can construct conversion factors between kilograms and grams as follows:

  21. Using Conversion Factors Section2 Describing Matter Chapter 1

  22. Chapter 1 Section2 Describing Matter Converting Units Sample Problem A Convert 0.851 L to milliliters.

  23. Chapter 1 Section2 Describing Matter Sample Problem A Solution • The equality that links the two units is 1000 mL = 1 L. (The prefix milli- represents 1/1000 of a base unit.) • The conversion factor needed must cancel liters and leave milliliters. Thus, liters must be on the bottom of the fraction and milliliters must be on the top.

  24. Section2 Describing Matter Chapter 1 Derived Units • Many quantities you can measure need units other than the seven basic SI units. • These units are derived by multiplying or dividing the base units. • Speedis distance divided by time.The derived unit of speed is meters per second (m/s). • A rectangle’sareais found by multiplying its length (in meters) by its width (also in meters). • Its unit is square meters (m2).

  25. Section2 Describing Matter Chapter 1 Derived Units, continued • Volume is another commonly used derived unit. • The volume of a book can be found by multiplying its length, width, and height. • The unit of volume is the cubic meter (m3). • This unit is too large and inconvenient in most labs. Chemists usually use the liter (L). • 1L = 1000 mL = 1000 cm3

  26. Section2 Describing Matter Chapter 1 Properties of Matter Physical Properties • Aphysical propertyof a substance is a characteristic that does not involve a chemical change. • Physical properties of a substance can be determined without changing the nature of a substance. • Physical properties include texture, state, melting point, and boiling point.

  27. Section2 Describing Matter Chapter 1 Properties of Matter, continued Density is the Ratio of Mass to Volume • Thedensityof an object is the mass of the object divided by volume of the object. • Densities are expressed in derived units such as g/cm3 or g/mL. • Density is calculated as follows:

  28. Chapter 1 Section2 Describing Matter Properties of Matter, continued Density of an Object • The density of a substance is the same no mater what the size of the sample is.

  29. Visual Concepts Chapter 1 Equation for Density

  30. Chapter 1 Section2 Describing Matter Properties of Matter, continued Density Can Be Used to Identify Substances • Because the density of a substance is the same for all samples, you can use this property to help identify substances.

  31. Section2 Describing Matter Chapter 1 Properties of Matter, continued Chemical Properties • Achemical propertya property of matter that describes a substance’s ability to participate in chemical reactions. • A chemical property of many substances is that they react with oxygen. • example: rusting • Some substances break down into new substances when heated.

  32. Visual Concepts Chapter 1 Comparing Physical and Chemical Properties

  33. Visual Concepts Chapter 1 Signs of a Chemical Reaction

  34. Section3 How Is Matter Classified? Chapter 1 Classifying Matter • Anatom is the smallest unit of an element that maintains the properties of that element. • Matter exists in many different forms but there are only 110 types of atoms. • Atoms are joined together to make up all the different kinds of matter.

  35. Section3 How Is Matter Classified? Chapter 1 Pure Substances • Apure substance is a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. • Elementsare pure substances that only contain one kind of matter. They cannot be separated or broken down into simpler substances by chemical means. • Each element has its own unique set of physical and chemical properties.

  36. Pure Substances Section3 How Is Matter Classified? Chapter 1

  37. Chapter 1 Section3 How Is Matter Classified? Elements are Pure Substances • Each elements is represented by a distinct chemical symbol.

  38. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Elements as Single Elements or Molecules • Amolecule is the smallest unit of a substance that keeps all of the physical and chemical properties of that substance. • A molecule usually consists of two or more atoms combined in a definite ratio. • Diatomicelements exist as two atoms of the same element joined together.

  39. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Some Elements Have More Than One Form • Some elements, such as oxygen, phosphorus, sulfur, and carbon, have many different molecular forms. • An allotrope is one of a number of different molecular forms of an element. • The properties of allotropes vary widely.

  40. Chapter 1 Section3 How Is Matter Classified? Pure Substances, continued Some Elements Have More Than One Form, continued • Oxygen exists as allotropes. • Oxygen gas (O2) is colorless and odorless. • Ozone (O3) is toxic and pale blue.

  41. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Compounds are Pure Substances • Pure substances that are not elements arecompounds.Compounds are composed of more than one kind of atom. • example: carbon dioxide (CO2) • There may be easier ways of preparing them, but compounds can be made from their elements. • Compounds can be broken down into their elements, though often with great difficulty.

  42. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Compounds are Represented by Formulas • Because every molecule of a compound is made up of the same kinds of atoms arranged the same way, a compound has characteristic properties and composition. • Compounds can be represented by an abbreviation orformula. • A formula has subscripts which represent the ratio of different atoms in the compound. • example: H2O has 2 hydrogen atoms and one oxygen atom

  43. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Compounds are Represented by Formulas, continued • Molecular formulasgive information only about what makes up a compound. • example: the molecular formula for aspirin is C9H8O4 • Astructural formulashows how the atoms are connected • This two-dimensional model does not show the molecule’s true shape.

  44. Section3 How Is Matter Classified? Chapter 1 Pure Substances, continued Compounds are Represented by Formulas, continued • Aball-and-stick modelshows the distances between atoms and the angles between them in three dimensions. • Aspace-filling modelattempts to represent the actual sizes of the atoms and not just their relative positions. • A hand-held model can provide more information than models shown on the flat surface of the page.

  45. Chapter 1 Section3 How Is Matter Classified? Pure Substances, continued Compounds are Represented by Formulas, continued • These models convey different information about acetylsalicylic acid (aspirin).

  46. Section3 How Is Matter Classified? Chapter 1 Mixtures • A mixture is a combination of two or more substances that are not chemically combined. • Air is a mixture of mostly nitrogen and oxygen. • All the different gases in air are physically mixed. • The proportions of the gases can vary. • Water is not a mixture. • The H and O atoms are chemically bonded • The ratio of H to O atoms is always 2 to 1.

  47. Section3 How Is Matter Classified? Chapter 1 Mixtures, continued Mixtures Can Vary in Composition and Properties • The proportion of the materials in a mixture can change. • The properties of the mixture may vary. • Analloyis a solid mixture. • example: An alloy of gold and other metal atoms is stronger than pure gold. • 18-karat gold contains 18 grams of gold per24 grams of alloy. • 14-karat gold contains 14 grams of gold per24 grams of alloy.

  48. Particle Models for Gold and Gold Alloy Chapter 1

  49. Section3 How Is Matter Classified? Chapter 1 Mixtures, continued Homogenous Mixtures • A homogenous mixture describes something that has uniform structure or composition throughout. • examples: gasoline, syrup, and air • Because any two samples of a homogenous mixture will have the same proportions of ingredients, homogenous mixtures have the same properties throughout.

  50. Section3 How Is Matter Classified? Chapter 1 Mixtures, continued Heterogeneous Mixtures • A heterogeneous mixture describes something that is composed of dissimilar components. • example: A mixture of sand and water is a heterogenous mixture. • Any two samples of a heterogeneous mixture will have the different proportions of ingredients. • Heterogeneous mixtures have different properties throughout.