Starter: Write Down What Type of Change?     

III. Classification of Matter (pp ) Matter Flowchart Pure Substances Mixtures III. Classification of Matter (pp ) Matter Flowchart Pure Substances Mixtures

A. Pure Substances Element composed of identical atoms EX: copper wire, aluminum foil Element composed of identical atoms EX: copper wire, aluminum foil

A. Pure Substances Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl) Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl)

B. Mixtures Variable combination of 2 or more pure substances. HeterogeneousHomogeneous

B. Mixtures Solution homogeneous very small particles particles don’t settle EX: rubbing alcohol Solution homogeneous very small particles particles don’t settle EX: rubbing alcohol

B. Mixtures Heterogeneous medium-sized to large-sized particles particles may or may not settle EX: milk, fresh- squeezed lemonade Heterogeneous medium-sized to large-sized particles particles may or may not settle EX: milk, fresh- squeezed lemonade

B. Mixtures Examples: tea muddy water fog saltwater Italian salad dressing Examples: tea muddy water fog saltwater Italian salad dressing Answers: Solution Heterogeneous Solution Heterogeneous

C. Matter Flowchart MATTER Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous MixtureCompoundElement MIXTUREPURE SUBSTANCE yes no Can it be chemically decomposed? noyes Is the composition uniform? noyes

C. Matter Flowchart Examples: graphite pepper sugar (sucrose) paint soda Examples: graphite pepper sugar (sucrose) paint soda element hetero. mixture compound hetero. mixture solution

D. Physical vs. Chemical Properties Examples: melting point flammable density magnetic tarnishes in air Examples: melting point flammable density magnetic tarnishes in air physical chemical physical chemical

E. Physical Changes Physical Change changes the form of a substance without changing its identity properties remain the same Examples: cutting a sheet of paper, breaking a crystal, all phase changes Physical Change changes the form of a substance without changing its identity properties remain the same Examples: cutting a sheet of paper, breaking a crystal, all phase changes

F. Chemical Changes Process that involves one or more substances changing into a new substance Commonly referred to as a chemical reaction New substances have different compositions and properties from original substances Process that involves one or more substances changing into a new substance Commonly referred to as a chemical reaction New substances have different compositions and properties from original substances

F. Chemical Changes Signs of a Chemical Change change in color or odor formation of a gas formation of a precipitate (solid) change in light or heat Signs of a Chemical Change change in color or odor formation of a gas formation of a precipitate (solid) change in light or heat

G. Physical vs. Chemical Changes Examples: rusting iron dissolving in water burning a log melting ice grinding spices Examples: rusting iron dissolving in water burning a log melting ice grinding spices chemical physical chemical physical

Chemical Reactions There are four clues that provide evidence of a chemical change: 1. Transfer of energy 2. Change in color 3. Production of a gas 4. Formation of a precipitate There are four clues that provide evidence of a chemical change: 1. Transfer of energy 2. Change in color 3. Production of a gas 4. Formation of a precipitate

Chemical Reactions Be careful, the clues are only indicators that a chemical change may have occurred. What is the only way to tell for sure that a chemical reaction has taken place? Be careful, the clues are only indicators that a chemical change may have occurred. What is the only way to tell for sure that a chemical reaction has taken place?

Law of Conservation of Mass During any chemical reaction, the mass of the products is equal to the mass of the reactants In any physical change or chemical reaction, matter can neither be created or destroyed. During any chemical reaction, the mass of the products is equal to the mass of the reactants In any physical change or chemical reaction, matter can neither be created or destroyed.