Classification of Matter Chapter 1 Chemistry 2-a

Chemistry: the field of study concerned with the characteristics, composition, and transformations of matter Matter: anything that has mass and occupies space Living and non-living Macroscopic and microscopic

States of Matter

Solids Definite shape Definite volume Atoms packed tightly together May be crystalline or amorphous Very low compressibility

Tro's "Introductory Chemistry", Chapter 3 Solids Some solids have their particles arranged in an orderly geometric pattern—we call these crystalline solids. Salt and diamonds. Other solids have particles that do not show a regular geometric pattern over a long range—we call these amorphous solids. Plastic and glass. Tro's "Introductory Chemistry", Chapter 3

Liquids No definite shape Definite volume Atoms close together, but not locked into place Low compressibility

Gases No definite shape No definite volume Atoms/Molecules far apart Compressible

Tro's "Introductory Chemistry", Chapter 3 Gases Because there is a lot of empty space, the particles can be squeezed closer together. Therefore, gases are compressible. Because the particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, and will flow. Tro's "Introductory Chemistry", Chapter 3

Classifying Matter by Physical State Matter can be classified as solid, liquid, or gas based on what properties it exhibits. Fixed = Property doesn’t change when placed in a container. Indefinite = Takes the property of the container. Tro's "Introductory Chemistry", Chapter 3

Classification of Matter 1. Pure Substances Element: a substance that cannot be decomposed or transformed into other chemical substances by ordinary chemical processes Atom: smallest particle of an element that can exist and still have the properties of that element Ex: Aluminum (Al), Carbon (C), Neon (Ne), Potassium (K)

Copper—A Pure Substance Color is brownish red. Shiny, malleable, and ductile. Excellent conductor of heat and electricity. Melting point = 1084.62 °C Density = 8.96 g/cm3 at 20 °C Tro's "Introductory Chemistry", Chapter 3

Compound: A substance consisting of two or more different atoms chemically bonded in a fixed ratio NaCl, CO2 Ionic compounds and molecules

Classification of Pure Substances Elements Compounds 1. Made of one type of atom. (Some elements are found as multi-atom molecules in nature.) 2. Combine together to make compounds. 1. Made of one type of molecule, or array of ions. 2. Molecules contain 2 or more different kinds of atoms. Tro's "Introductory Chemistry", Chapter 3

Practice—Classify the Following as Elements or Compounds, Continued Chlorine, Cl2 = element. Table sugar, C12H22O11 = compound. A red solid that turns blue when heated and releases water that is always 30% of the solid’s mass = compound. A brown-red liquid that, when energy is applied to it in any form, causes only physical changes in the material, not chemical = element. Tro's "Introductory Chemistry", Chapter 3

2. Mixtures Mixtures: combinations of two or more pure substances in which each substance retains its own identity Heterogeneous Mixture: a substance in which elements and/or compounds are blended together in such a way that there is no uniform composition or fixed ratio of the components of the mixture Examples: Oil and water, mixed nuts

Homogeneous Mixture: A substance in which the different elements/compounds being mixed exist in definite ratios, but are not chemically bonded Consists of two or more substances in the same phase No amount of magnification will reveal an interface Called a “solution” Examples: Salt water, sugar water, O2 dissolved in water

musical instruments and clock dials Brass—A Mixture Type Color % Cu % Zn Density g/cm3 MP °C Tensile Strength psi Uses Gilding reddish 95 5 8.86 1066 50K pre-83 pennies, munitions, and plaques Commercial bronze 90 10 8.80 1043 61K door knobs and grillwork Jewelry 87.5 12.5 8.78 1035 66K costume jewelry Red golden 85 15 8.75 1027 70K electrical sockets, fasteners, and eyelets Low deep yellow 80 20 8.67 999 74K musical instruments and clock dials Cartridge yellow 70 30 8.47 954 76K car radiator cores Common 67 33 8.42 940 lamp fixtures and bead chain Muntz metal 60 40 8.39 904 nuts and bolts

Practice—Classify the Following as Homogeneous or Heterogeneous Table sugar. A mixture of table sugar and black pepper. A mixture of sugar dissolved in water. Oil and vinegar salad dressing. Tro's "Introductory Chemistry", Chapter 3

Classifying Matter

Tro's "Introductory Chemistry", Chapter 3 Practice—Classify the Following as Pure Substances or Mixtures, Continued A homogeneous liquid whose temperature stays constant while boiling = pure substance. Granite—a rock with several visible minerals in it = mixture. A red solid that turns blue when heated and releases water that is always 30% of the solid’s mass = pure substance. A gas that when cooled and compressed, a liquid condenses out but some gas remains = mixture. Tro's "Introductory Chemistry", Chapter 3

Physical Properties Properties of an object or substance that can be measured or perceived without changing the identity of the substance

Some Physical Properties of Iron Iron is a silvery solid at room temperature with a metallic taste and smooth texture. Iron melts at 1538 °C and boils at 4428 °C. Iron’s density is 7.87 g/cm3. Iron can be magnetized. Iron conducts electricity, but not as well as most other common metals. Iron’s ductility and thermal conductivity are about average for a metal. It requires 0.45 J of heat energy to raise the temperature of one gram of iron by 1°C. Tro's "Introductory Chemistry", Chapter 3

Physical Change A change in a physical property of a substance Same substance before and after the change

Changes in State

Phase Changes Are Physical Changes Boiling = liquid to gas. Melting = solid to liquid. Subliming = solid to gas. Freezing = liquid to solid. Condensing = gas to liquid. Deposition = gas to solid. State changes require heating or cooling the substance. Evaporation is not a simple phase change, it is a solution process. Tro's "Introductory Chemistry", Chapter 3

Chemical Change A process in which reactants are changed into one or more different products Have breaking and making of chemical bonds

Some Chemical Properties Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Changes in Matter Chemical Changes involve a change in the properties of matter that change its composition. A chemical reaction. Rusting is iron combining with oxygen to make iron(III) oxide. Burning results in butane from a lighter to be changed into carbon dioxide and water. Silver combines with sulfur in the air to make tarnish. Tro's "Introductory Chemistry", Chapter 3

Some Chemical Properties of Iron Iron is easily oxidized in moist air to form rust. When iron is added to hydrochloric acid, it produces a solution of ferric chloride and hydrogen gas. Iron is more reactive than silver, but less reactive than magnesium. Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Changes in Matter Changes that alter the state or appearance of the matter without altering the composition are called physical changes. Changes that alter the composition of the matter are called chemical changes. During the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present. Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Practice—Decide Whether Each of the Observations About Table Salt Is a Physical or Chemical Property Salt is a white, granular solid. Salt melts at 801 °C. Salt is stable at room temperature, it does not decompose. 36 g of salt will dissolve in 100 g of water. Salt solutions and molten salt conduct electricity. When a clear, colorless solution of silver nitrate is added to a salt solution, a white solid forms. When electricity is passed through molten salt, a gray metal forms at one terminal and a yellow-green gas at the other. Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Practice − Decide Whether Each of the Observations About Table Salt Is a Physical or Chemical Property Salt is a white, granular solid = physical. Salt melts at 801 °C = physical. Salt is stable at room temperature, it does not decompose = chemical. 36 g of salt will dissolve in 100 g of water = physical. Salt solutions and molten salt conduct electricity = physical. When a clear, colorless solution of silver nitrate is added to a salt solution, a white solid forms = chemical. When electricity is passed through molten salt, a gray metal forms at one terminal and a yellow-green gas at the other = chemical. Tro's "Introductory Chemistry", Chapter 3

Practice—Classify Each Change as Physical or Chemical Evaporation of rubbing alcohol. Sugar turning black when heated. An egg splitting open and spilling out. Sugar fermenting. Bubbles escaping from soda. Bubbles that form when hydrogen peroxide is mixed with blood. Tro's "Introductory Chemistry", Chapter 3

Problems Decide whether the following are chemical or physical changes Sawing a log in half Melting chocolate in a pot on your stove Burning your chocolate Dissolving a nickel in acid Cutting your hair

Separation of Mixtures Separate mixtures based on different physical properties of the components. Physical change. Centrifugation and decanting Density Evaporation Volatility Chromatography Adherence to a surface Filtration State of matter (solid/liquid/gas) Distillation Boiling point Technique Different Physical Property Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Distillation Tro's "Introductory Chemistry", Chapter 3

Tro's "Introductory Chemistry", Chapter 3 Filtration Tro's "Introductory Chemistry", Chapter 3