Matter and Change Chapter 3

Matter Everything around us Everything around us Can be substances Can be substances (pure) by definition, with uniform and unchanging composition (pure) by definition, with uniform and unchanging composition Can be mixtures Can be mixtures Salt water Salt water Nitrogen and oxygen (AIR) Nitrogen and oxygen (AIR)

Physical Properties of Matter Characteristics or behavior Characteristics or behavior Can identify substance Can identify substance Examples Examples Phys. State at partic. temperature Phys. State at partic. temperature Melting point, boiling point Melting point, boiling point Density [g/cm 3 or g/mL or g/L] Density [g/cm 3 or g/mL or g/L] Extensive: depends on amount of substance Extensive: depends on amount of substance

Extensive: depends on amount of substance. Ex: mass or volume of substance. Extensive: depends on amount of substance. Ex: mass or volume of substance. Intensive: Independent of amount of substance. (Ex.: density, color, b.pt.) Intensive: Independent of amount of substance. (Ex.: density, color, b.pt.)

Chemical Properties Ability (or lack of it) to combine or change into a different substance. Ability (or lack of it) to combine or change into a different substance. Iron (Fe) forms rust when exposed to oxygen in air. (FeO) Iron (Fe) forms rust when exposed to oxygen in air. (FeO) Iron does not combine with nitrogen in air. Iron does not combine with nitrogen in air. See properties of copper p. 57 See properties of copper p. 57

States of Matter Solid: particles tightly packed, vibrate in place, object has def. shape (indep. of container). Solid: particles tightly packed, vibrate in place, object has def. shape (indep. of container). Liquid: particles slip past each other, definite volume, indefinite shape, dep. on container. Liquid: particles slip past each other, definite volume, indefinite shape, dep. on container. Gas: fills entire container, particles don’t affect each other, shape & volume depends on container. Gas: fills entire container, particles don’t affect each other, shape & volume depends on container. Vapor is not always a gas. Might be a liquid. Vapor is not always a gas. Might be a liquid.

Physical and Chemical Changes Physical changes: altering a substance without changing its composition. Physical changes: altering a substance without changing its composition. Ex. Cutting, breaking, bending, grinding, crumpling, crushing, etc. Ex. Cutting, breaking, bending, grinding, crumpling, crushing, etc. Also : condensation, boil’g, freez’g, vaporiz’g, melt’g. Also : condensation, boil’g, freez’g, vaporiz’g, melt’g. (Phase changes are PHYSICAL changes) (Phase changes are PHYSICAL changes) Many times reversible. Many times reversible.

Chemical Changes When a new substance is formed. When a new substance is formed. Iron rusting, food digesting, gasoline exploding. Iron rusting, food digesting, gasoline exploding. EVIDENCES of CHEM CHANGE EVIDENCES of CHEM CHANGE Energy change (heat absorbed or released) Energy change (heat absorbed or released) Gas or odor produced Gas or odor produced Color change Color change Formation of a new solid Formation of a new solid

Conservation of Mass Chem. rxns. been observed since we have observed world. Chem. rxns. been observed since we have observed world. Late 18 th century (1700’s) these were 1 st quantified (measured). Late 18 th century (1700’s) these were 1 st quantified (measured). Lavoisier discovered the Law of Conservation of Mass Lavoisier discovered the Law of Conservation of Mass Mass is not created nor destroyed during chem. reaction; it is conserved. P.64, prob. P.65 Mass is not created nor destroyed during chem. reaction; it is conserved. P.64, prob. P.65

Mixtures of Matter Mixture: combination of 2 or more substances in which each retains its individual properties. Mixture: combination of 2 or more substances in which each retains its individual properties. Composition varies Composition varies Number of mixtures possible is infinite Number of mixtures possible is infinite Can be separated by differences in physical properties. Can be separated by differences in physical properties.

Methods of Separation Reaction to a magnetic field Reaction to a magnetic field Filtration of a solid from a liquid Filtration of a solid from a liquid Distillation of 2 or more liquids from each other, based on diff. boil’g. pts. Distillation of 2 or more liquids from each other, based on diff. boil’g. pts. Crystallization: sep. 2 solids from each other. Crystallization: sep. 2 solids from each other. Chromatography: based on chem. polarity diff. of molecules. Chromatography: based on chem. polarity diff. of molecules.

Types of Mixtures Heterogeneous: individual parts or phases distinctly seen. Heterogeneous: individual parts or phases distinctly seen. Homogeneous: looks the same throughout Homogeneous: looks the same throughout Can be solutions Can be solutions Top same as bottom Top same as bottom Ex vanilla ice cream, margarine, mixed koolaid Ex vanilla ice cream, margarine, mixed koolaid

Elements and Compounds Elements and Compounds are both types of pure substances Elements and Compounds are both types of pure substances Element : cannot be divided further by physical or chem. means. Element : cannot be divided further by physical or chem. means. Smallest unit is the atom. Smallest unit is the atom. 91 natural ones, rest man-made. 91 natural ones, rest man-made.

Periodic Table Chart organized according to their chem. activity. Chart organized according to their chem. activity. Horiz. rows called periods. Horiz. rows called periods. Vertical columns called groups or families. Vertical columns called groups or families. Predictions can be made from it. Predictions can be made from it. Mendeleev developed 1 st one. Mendeleev developed 1 st one.

Compounds 2 or more elements chemically bonded together. 2 or more elements chemically bonded together. Smallest unit is a molecule (atoms bonded together) Smallest unit is a molecule (atoms bonded together) Ex. Water, H 2 O, salt, NaCl, sugar, C 12 H 22 O 11 Ex. Water, H 2 O, salt, NaCl, sugar, C 12 H 22 O million cpds known, 100,000 new each yr. 10 million cpds known, 100,000 new each yr.

Law of Definite Proportions A compound is always composed of the same elements in the same proportions. A compound is always composed of the same elements in the same proportions. Water is always 11% H and 89% O. Water is always 11% H and 89% O. CO 2 is always 27.3% C, 72.7% O. CO 2 is always 27.3% C, 72.7% O. Table on p.75 Table on p.75 Prac. Prob. P.76 Prac. Prob. P.76

 Compounds can be broken into elements they are made of.  Liquid H 2 O→ H 2 gas+ O 2 gas p.74  NaCl crystals → Na solid + Cl 2 gas p.74

Law of Multiple Proportions When 2 elements combine to produce 2 different compounds, the mass of one element that combines with a given amunt of the other element will vary by small whole number ratios. When 2 elements combine to produce 2 different compounds, the mass of one element that combines with a given amunt of the other element will vary by small whole number ratios. Ex. CO and CO 2 :12 grams C combine with 16 grams O in CO, but in CO 2 12 grams C combine with 32 grams O(twice as much O). Table p.76 Ex. CO and CO 2 :12 grams C combine with 16 grams O in CO, but in CO 2 12 grams C combine with 32 grams O(twice as much O). Table p.76

Some differences in these 2 laws: Some differences in these 2 laws: Law of def. proport. deals with 1 compound only. Law of def. proport. deals with 1 compound only. Law of mult. proport. Deals with 2 compounds at a time. Law of mult. proport. Deals with 2 compounds at a time. Other ex. NO 2 and N 2 O 3, Other ex. NO 2 and N 2 O 3, or PCl 3 and PCl 5, or SF 4 and SF 6. or PCl 3 and PCl 5, or SF 4 and SF 6.