CHAPTER 3 MATTER ENERGY Problems 1 50 57 58 61 74 107 109 115 3 2 What is Matter Matter Anything that has mass and occupies volume We study matter at different levels macroscopic the level that can be observed with the naked eye e g geologists study rocks and stone at the macroscopic level microscopic the level that can be observed with a microscope e g scientists study tiny animals plants or crystals at microscopic level particulate at the level of atoms and molecules also called atomic or molecular level cannot be observed directly even with the most powerful microscopes where the term nanotechnology comes from since many atoms and molecules are about a few nanometers in size Substances like water can be represented using different symbols e g H2O and models CHEM 121 Tro Chapter 3 page 1 of 13 3 3 Classifying Matter According to Its State Solid Liquid and Gas Matter exists in one of three physical states solid liquid gas solid Has definite shape and a fixed or constant and rigid volume Particles only vibrate in place liquid Has a fixed or constant volume but its shape can change Takes the shape of its container because particles are moving Particles are packed closely together but can move around each other gas Volume is variable and particles are far apart from one another Takes the shape of the container because particles are moving If container volume expands particles move apart to fill container If container volume decreases particles move closer together Gases are compressible i e can be forced to occupy a smaller volume Particles are in constant random motion CHEM 121 Tro Chapter 3 page 2 of 13 3 4 Classifying Matter According to Its Composition Elements Compounds and Mixtures We can classify matter into pure substances and mixtures pure substance a single chemical consisting of only one kind of matter There are two types of pure substances elements and compounds In the figure below copper rods are an example of an element and sugar is an example of a compound mixture consists of two or more elements and or compounds Mixtures can be homogeneous or heterogeneous Homogeneous mixtures have a uniform appearance and composition because the particles in them mix uniformly e g solutions like sweetened tea below Heterogeneous mixtures do not have a uniform composition e g chocolate chip cookie water and C8H18 mixture below shown as separate layers CHEM 121 Tro Chapter 3 page 3 of 13 elements consist of only one type of atom atoms cannot be broken down into smaller components by chemical reaction e g copper wire Cu sulfur powder S8 Examples also include sodium Na barium Ba hydrogen gas H2 oxygen gas O2 and chlorine gas H2 compounds consist of more than one type of atom and have a specific chemical formula Examples include hydrogen chloride HCl water H2O sodium chloride NaCl which is table salt barium chloride BaCl2 Two or more pure substances combine to form mixtures mixtures consist of many compounds and or elements with no specific formula Matter having variable composition with definite or varying properties can be separated into component elements and or compounds e g any alloy like brass steel 10K to 18K gold sea water carbonated soda air consists of nitrogen oxygen and other trace gases The image at the right shows that air is a mixture of mostly nitrogen N2 in blue and some oxygen O2 in red while salt water consists of salt Na and Cl ions or charged particles dissolved in water Example Is salt water a homogeneous or heterogeneous mixture Explain CHEM 121 Tro Chapter 3 page 4 of 13 3 5 How We Tell Different Kinds of Matter Apart Physical and Chemical Properties The characteristics that distinguish one substance from another are called properties Physical Properties inherent characteristics of a substance independent of other substances physical state solid liquid gas electrical heat conductivity color odor density hardness melting and boiling points solubility does does not dissolve in water Chemical Properties how a substance reacts with other substances e g hydrogen reacts explosively with oxygen 3 6 How Matter Changes Physical and Chemical Changes physical change a process that does not alter the chemical makeup of the starting materials Note in the figure below that the H2O molecules remain H2O regardless of the physical state solid liquid or gas Changes in physical state are physical changes Other examples of physical changes include hammering gold into foil dry ice subliming Dissolving table salt or sugar in water is also a physical change A substance dissolved in water is the fourth physical state aqueous CHEM 121 Tro Chapter 3 page 5 of 13 Know the terms for transitions from one physical state to another freezing melting liquid solid solid liquid condensing gas liquid evaporating or vaporizing liquid gas Two less common transitions sublimation solid gas e g dry ice sublimes deposition gas solid e g water vapor deposits on an icebox chemical change a process that does change the chemical makeup of the starting materials We can show H2 and O2 reacting to form water H2O below Since the H2O has a different chemical makeup than H2 and O2 this is a chemical change Other examples of chemical changes e g oxidation of matter burning or rusting release of gas bubbles fizzing mixing two solutions to form an insoluble solid precipitation and other evidence indicating the starting materials reactants were changed to a different substance The following examples are all chemical changes that convert the reactants to completely different compounds and or elements release of gas bubbles fizzing formation of insoluble solid precipitation oxidation burning or rusting CHEM 121 Tro Chapter 3 page 6 of 13 Example 1 Consider the following molecular level representations of different substances A B C D E F For each figure above indicate if it represents an element a compound or a mixture AND if it represents a solid liquid or gas A element compound mixture solid liquid gas B element compound mixture solid liquid gas C element compound mixture solid liquid gas D element compound mixture solid liquid gas E element compound mixture solid liquid gas F element compound mixture solid liquid gas Ex 2 Circle all of the following that are chemical changes burning condensing CHEM 121 Tro Chapter 3 dissolving rusting vaporizing precipitating page 7 of 13 3 7 Conservation of Mass There is No New Matter Chemical Reaction REACTANTS starting materials For the reaction C O2 PRODUCTS substances after