Classification of Matter Chapter 2

Objectives LWBAT: 1.Describe the characteristics of physical and chemical properties. 2.Classify mixtures as homogenous or heterogeneous. 3.Describe the characteristics of physical and chemical changes.

What is matter? Matter is anything that has mass and takes up space.

Materials Specific types of matter Described according to phases (solid, liquid, gas)

Pure Substances Contain only one type of matter Cannot be separated physically Has a fixed composition (structure)

Pure Substances Elements - simplest pure substances made of only one type of atom (Periodic Table) Cannot be broken down into a simpler substances.

Pure Substances Compounds - – two or more elements chemically combined (H 2 O, CuSO 4 ) Always in a fixed proportion (relationship)

Mixtures Physical combination of two or more substances Can be separated physically

Heterogeneous Mixtures Prefix “Hetero-” means different Substances can be easily distinguished and separated Ex: sand and salt, trail mix, sand and gravel, salad

Homogeneous Mixtures Prefix “Homo-” means same Substances are well mixed and appear the same throughout Ex: Solution

Solutions Solute dissolves in solvent to form solution. (solute + solvent = solution) Concentrated solution contains more solute than dilute solution. Ex: Kool-Aid, iced tea, coffee

Physical Properties (appearance changes but materials stays the same) Describe substances undergoing physical changes Ex: viscosity, conductivity, malleability, hardness, density, boiling point and melting point

Viscosity The tendency of a liquid to keep from flowing—its resistance to flowing. Example: Honey – high viscosityVinegar – low viscosity

Conductivity A material’s ability to allow heat to flow High conductivity – metal spoonLow conductivity – wooden spoon

Malleability Ability of a solid to be hammered without shattering

Hardness One way to compare the hardness of two materials is to see which of the materials can scratch the other.

Density Can be used to test the purity of a substance Formula: mass/volume Example: testing fuel in motorcycles

Melting and Boiling Points Melting point – temperature at which a substance changes from a solid to a liquid Boiling point – temperature in which a substance boils (liquid to a gas)

Additional Physical Properties Color Shape (structure) Texture (how the material feels)

Using Properties to Separate Mixtures Filtration – a process that separates materials based on the size of the particles. Distillation – a process that separates the substances in a solution based on their boiling point.

Chemical Properties Describe substances undergoing chemical changes Ex: flammability, reactivity

Flammability A material’s ability to burn in the presence of oxygen.

Reactivity The property that describes how a substance combines chemically with other substances; forms a new substance Iron + water = rust

Is it a chemical or physical change? When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.

Law of Conservation of Matter Matter is not created or destroyed during a physical or chemical change Physical ChangeChemical Change

Physical Changes Same substance remains after change Used to separate mixtures Ex: pounding, tearing, cutting, dissolving, evaporating, melting, boiling, pulling

Chemical Changes Results in new substance with new properties Also known as a chemical reaction Ex: burning, digesting, fermenting, decomposing

Chemical Change Evidence 1. Precipitate forms (solid) 2. Gas evolves (bubbles) 3. Color change (tarnishing) 4. Energy change Exothermic = releases energy Endothermic = absorbs energy 5. Odor produced (sometimes)