CHAPTER 2 Matter and Change

B. Physical Properties 1. can be observed without changing the chemical composition 2. Examples  Color  Melting point  Density  Hardness  Malleability

C. Chemical Properties 1. determined by how a chemical reacts (or doesn’t) with another chemical 2. Examples –  Rusts  Reacts with HCl  Reacts with water

Physical or Chemical Property? 7) Water boils at 100°C. 8) Zinc reacts with hydrochloric acid. 9) Sodium chloride dissolves in water. 10) Aluminum is shiny silver in color. 11) Copper is ductile. 12) Calcium reacts with water. 13) The density of aluminum is 2.7 g / mL.

D. States of Matter Solids a) definite mass? b) definite volume? c) definite shape? d) compressible? e) able to flow?

D. States of Matter Liquids a) definite mass? b) definite volume? c) definite shape? d) can be compressed? e) flows?

D. States of Matter Gases a) definite mass? b) definite volume? c) definite shape? d) can be compressed? e) flows?

D. States of Matter 1) summary chart PropertySolidLiquidGas MassFixed VolumeFixed Volume of container Flows?NoYes ShapeFixedShape of container Compressible?No yes Expands?No yes

D. States of Matter 2) Vapors  a) = substances in the gaseous state which are usually in the liquid or solid state at room temperature  b) ex. – gasoline fumes, moth ball odors, steam, “fog” from dry ice

E. Classification of Matter 1. Substances = definite or fixed composition  can write a chemical formula for it  pure

E. Classification of Matter 1. Substances  a) Elements  Listed on periodic table  Mg, Ne, Cl, C, etc.

E. Classification of Matter 1. Substances  b) Compounds  Contain two or more elements in fixed ratio  Ex. – NaCl, CO, H 2 O

E. Classification of Matter 2. Mixtures = composition is NOT fixed or definite; it varies  Cannot write a formula for it

E. Classification of Matter 2. Mixtures  a) homogeneous mixtures *uniform (same throughout) *one phase *also called solutions (but can be s, l or g) *ex. – saline solution, tap water, brass, hot tea, air

E. Classification of Matter 2. Mixtures  b) heterogeneous mixtures  *not uniform  *two or more phases  *ex. – soil, fresh-squeezed orange juice, sand and water

F. How to separate parts of a mixture? 1. Magnetism

F. How to separate parts of a mixture? 2. Filtration

F. How to separate parts of a mixture? 3. Density

F. How to separate parts of a mixture? 4. Distillation  (different boiling points)

F. How to separate parts of a mixture? 5. Chromatography  (ex. – paper + ink)

G. Changes 1. Physical Changes  a) chemical composition of material does NOT change  b) may be reversible  c) examples  Tearing paper  Boiling water  Crushing salt  Crumpling foil

G. Changes 2. Chemical changes  a) change in chemical composition  b) examples  Iron rusting  Zinc + hydrochloric acid  Digestion of food  Burning wood  Lithium + water

H. Clues for a chemical change (reaction) 1. formation of bubbles (gas) Ex. – metal + acid

H. Clues for a chemical change (reaction) 2. formation of precipitate (insoluble powder)

H. Clues for a chemical change (reaction) 3. release or absorption of energy (heat or light) Ex. – burning of wood

H. Clues for a chemical change (reaction) 4. change in color  Ex. – meat changes color when cooked  Ex. – changing in color of leaves in fall

H. Clues for a chemical change (reaction) 5. change in pH (acidity level)

I. Sometimes the “clues” indicate a physical change! 1. color change could be dilution (ex. – add water to Kool-Aid) 2. bubbles could be boiling liquid 3. heat absorbed during a change in state (ex. - melting ice)

J. Law of conservation of mass 1. Mass cannot be created or destroyed in a chemical reaction or physical change