* mixture composed of * mixture that consists * substance composed * substance composed of * mixture composed of * mixture that consists * substance composed * substance composed of more than one phase of only one phase of only one type of atom two or more kinds of atoms more than one phase of only one phase of only one type of atom two or more kinds of atoms (regions with uniform microscopically ex.: gold, aluminum, ex.: salt, sugar, water, (regions with uniform microscopically ex.: gold, aluminum, ex.: salt, sugar, water, properties; interphase - indistinguishable parts carbon hydrogen peroxide properties; interphase - indistinguishable parts carbon hydrogen peroxide boundary between regions ex.: saltwater, window different properties than boundary between regions ex.: saltwater, window different properties than ex.: oil and water, glass, air, copper individual elements ( O and ex.: oil and water, glass, air, copper individual elements ( O and granite sulfate H – gases and H 2 O – liquid) granite sulfate H – gases and H 2 O – liquid) * solutions can vary in * solutions can vary in composition and consist composition and consist of a solvent (greater amount) of a solvent (greater amount) and one or more solutes and one or more solutes (lesser amounts) (lesser amounts)

Pure Substances * a form of matter that has uniform and unchanging composition Elements Elements Cannot be separated into simpler substances by physical or chemical means Cannot be separated into simpler substances by physical or chemical means Consists of only one type of atom Consists of only one type of atom Unique physical & chemical properties Unique physical & chemical properties 91 naturally occurring, others are manmade. 91 naturally occurring, others are manmade. What is the most abundant element in the earth’s crust? What is the most abundant element in the earth’s crust? Compounds Compounds Combination of 2 or more elements combined chemically Consists of two or more types of atoms Totally different physical & chemical properties from the elements they are composed of. Millions of different kinds Examples: water, salt, sucrose, aspirin, baking soda, plastics, proteins, fats,

Mixtures * a combination of two or more pure substances in which each retains its properties. The composition of a mixture can vary. Heterogeneous Heterogeneous Has 2 or more phases (areas with a uniform set of properties) with an interphase(boundary) between them. Has 2 or more phases (areas with a uniform set of properties) with an interphase(boundary) between them. The substances in this remain distinct. The substances in this remain distinct. Examples: dirt, blood, whole milk that’s not homogenized, oil and water mixture, granite, orange juice, sand Examples: dirt, blood, whole milk that’s not homogenized, oil and water mixture, granite, orange juice, sand Homogeneous Homogeneous Has only one phase with microscopically indistinguishable parts. Also know as solutions They consist of a solvent (material in greater amount) and solute (material in lesser amount) Examples: salt water, glass, air, copper sulfate solution, brass, steel

Means of Separating Mixtures Filtration - uses a porous barrier to separate a solid from a liquid Filtration - uses a porous barrier to separate a solid from a liquid Distillation - separation based on boiling point differences of two or more substances Distillation - separation based on boiling point differences of two or more substances Crystallization - separation based on solubility differences of solutes in a solution. Solutes precipitate out at different rates Crystallization - separation based on solubility differences of solutes in a solution. Solutes precipitate out at different rates Chromatography - Separation of components from a mixture (called the mobile phase) as they travel across the surface of another material (called the stationary phase) Chromatography - Separation of components from a mixture (called the mobile phase) as they travel across the surface of another material (called the stationary phase)

Law of Definite Proportions A compound is always composed of the same elements in the same proportion by mass A compound is always composed of the same elements in the same proportion by mass In order to see this law in effect, we need to know how to calculate percent by mass. In order to see this law in effect, we need to know how to calculate percent by mass. percent by mass (%) = mass of element percent by mass (%) = mass of element mass of compound mass of compound x 100

Law of Definite Proportions Regardless of the amount, water will always be composed of 11.1% hydrogen and 88.9% oxygen. Regardless of the amount, water will always be composed of 11.1% hydrogen and 88.9% oxygen. Note: atoms always combine in whole number combinations and definite proportions to create compounds. Note: atoms always combine in whole number combinations and definite proportions to create compounds. Element Mass (g) Percent by mass (%) Hydrogen 11.1 g 11.1 g x 100 = 11.1 % 100 g Oxygen 88.9 g 88.9 x 100 = 88.9 % 100 Total 100 g = 100 % = 100 % Element Mass (g) Percent by mass (%) Hydrogen g g x 100 = 11.1 % 250 g 250 g Oxygen g x 100 = 88.9 % Total 250 g = 100 % = 100 % 100 g sample of water 250 g sample of water

Percent by Mass If 5 g of X reacts with 15 g of Y to form the compound XY, what is the percent by mass of X in the compound? The percent by mass of Y? If 5 g of X reacts with 15 g of Y to form the compound XY, what is the percent by mass of X in the compound? The percent by mass of Y? 5g / 20g x 100 = 25% X 5g / 20g x 100 = 25% X 15g / 20g x 100 = 75% Y 15g / 20g x 100 = 75% Y

Law of Multiple Proportions When different compounds are formed by the same elements, different masses of one element combine with the same relative mass of the other element in whole number ratios. When different compounds are formed by the same elements, different masses of one element combine with the same relative mass of the other element in whole number ratios.

Law of Multiple Proportions mass ratio for H 2 O 2 16 mass ratio for H 2 O 2 16 mass ratio for H 2 O 8 mass ratio for H 2 O 8 Compound % H % O Mass H (g) in 100 g of compound Mass O (g) in 100 g of compound Mass ratio mass O mass H H2OH2OH2OH2O H2O2H2O2H2O2H2O == 2 The different masses of oxygen that combine with a fixed mass of hydrogen in the two different compounds can be expressed as a small whole number ratio.

Physical Properties – a characteristic that can be observed without changing the substance Intensive Intensive Properties that do not depend on the amount of the substance Properties that do not depend on the amount of the substance Examples Examples Density Density Boiling point Boiling point Melting point Melting point Color Color Conductivity Conductivity Hardness Hardness Odor Odor Ductility- can be pulled into wire Ductility- can be pulled into wire Malleability- can be hammered into thin sheet Malleability- can be hammered into thin sheet Extensive Extensive Properties dependent upon the amount of the substance present Examples Mass Length Volume area

Chemical Properties Characteristics that depend on the action of a substance with other substances (how it reacts or does not react) Characteristics that depend on the action of a substance with other substances (how it reacts or does not react) Examples Examples Does it burn in air? Does it burn in air? Does it react with water? Does it react with water? How does it react with acids and/or bases? How does it react with acids and/or bases? Is it relatively inert? Is it relatively inert? (see page 57 for examples with copper) (see page 57 for examples with copper)

States of Matter solid liquid gas solid liquid gas Definite shape Definite volume No compressibility (particles tightly packed) Very little motion/ vibration/kinetic energy T akes shape of container Constant volume No compressibility (particles are close, but less packed and can slide past ea. other) More motion/ vibration/kinetic energy Takes shape of container Changeable volume Easily compressed (particles far apart) Very high motion/ vibration/kinetic energy

Physical Change A type of change that alters physical properties, but does not change the composition of a substance A type of change that alters physical properties, but does not change the composition of a substance Examples Examples Crumpling paper Crumpling paper Cutting wood Cutting wood Crushing a can Crushing a can Phase change (change of state) Phase change (change of state)

Chemical Change A process that involves one or more substances changing into new substances (chemical reaction); products have different compositions with different chemical properties A process that involves one or more substances changing into new substances (chemical reaction); products have different compositions with different chemical properties Examples Examples Rusting Rusting Combustion Combustion Fermentation Fermentation Metabolism Metabolism Indicators of Chemical Change: (1) temp change (2) gas produced (3) precipitate formed (4) color change (5) light produced (6) sound produced or an explosion (7) new odor produced Indicators of Chemical Change: (1) temp change (2) gas produced (3) precipitate formed (4) color change (5) light produced (6) sound produced or an explosion (7) new odor produced

Conservation of Mass Mass is neither created nor destroyed Mass is neither created nor destroyed Mass reactants = Mass products Mass reactants = Mass products Example 1 What mass of MgO is produced when 200 g of Mg react with 16 g of O 2 ? Example 1 What mass of MgO is produced when 200 g of Mg react with 16 g of O 2 ? 2Mg + O 2 2 MgO 2Mg + O 2 2 MgO 200 g + 16 g = ? g 200 g + 16 g = ? g 216g = 216 g 216g = 216 g

Conservation of Mass Example 2: If g of sodium combines with chlorine gas to form g of sodium chloride, what mass of chlorine gas is used in the reaction? Example 2: If g of sodium combines with chlorine gas to form g of sodium chloride, what mass of chlorine gas is used in the reaction? Solution Solution sodium + chlorine --> sodium chloride sodium + chlorine --> sodium chloride 45.98g + ?g g 45.98g + ?g g g g= 70.91g g g= 70.91g

Conservation of Mass Example 3: Copper sulfide is formed when copper and sulfur are heated together. In this reaction 127 g of copper react with 41 g of sulfur. After the reaction is complete 9g of sulfur remains unreacted. What is the mass of copper sulfide formed? Example 3: Copper sulfide is formed when copper and sulfur are heated together. In this reaction 127 g of copper react with 41 g of sulfur. After the reaction is complete 9g of sulfur remains unreacted. What is the mass of copper sulfide formed? Copper + sulfur --> Copper sulfide Copper + sulfur --> Copper sulfide 127g + 41g - 9g --> ? g 127g + 41g - 9g --> ? g g = 159g g = 159g