Laws and theories Law – a generalization that describes the behavior of nature. i.e. Law of Definite Proportions Theory – an explanation of observations i.e. Dalton’s atomic theory

Matter Anything that has mass and takes up space Anything that has mass and takes up space

States of Matter StateShapeVolumeCompressible? SolidDefiniteDefiniteNo LiquidIndefiniteDefiniteNo GasIndefiniteIndefiniteyes

Physical properties A quality which can be determined without changing the identity of the material A quality which can be determined without changing the identity of the material Freezing point Freezing point Boiling point Boiling point Color Color Odor Odor Hardness Hardness Density Density Solubility Solubility

Extensive Properties Extensive Properties Depend on how much (the extent) matter there is Depend on how much (the extent) matter there is i.e. length, mass, volume i.e. length, mass, volume Intensive Properties Intensive Properties Do NOT depend on how much matter there is Do NOT depend on how much matter there is i.e. temperature, density (m/V) i.e. temperature, density (m/V)

Steel Adding the following elements (besides carbon) to iron produces steel with these resulting properties. Adding the following elements (besides carbon) to iron produces steel with these resulting properties. Cr - adds corrosion resistance Cr - adds corrosion resistance Si - improves machinability and weldability Si - improves machinability and weldability V - adds strength V - adds strength Mo - adds strength Mo - adds strength Ni - changes the microstructure, can improve toughness Ni - changes the microstructure, can improve toughness Nb - improves creep resistance with proper heat treatment Nb - improves creep resistance with proper heat treatment Al - removes oxygen to improve strength Al - removes oxygen to improve strength B - helps to prevent cracking B - helps to prevent cracking N - can improve strength by forming nitrides N - can improve strength by forming nitrides

Chemical Properties Describe the behavior of a material in reactions that change its identity Describe the behavior of a material in reactions that change its identity Combustibility Combustibility Reactivity with other substances Reactivity with other substances

General classes of elements Metals – have luster (shine) Metals – have luster (shine) are malleable (not brittle) are ductile (can be drawn into wires) conduct heat and electricity Nonmetals- poor conductors of heat and electricity Nonmetals- poor conductors of heat and electricitybrittle Metalloids- have characteristics of metals and nonmetals Metalloids- have characteristics of metals and nonmetals

Classes of matter Matter Pure substance elementcompound mixture homogeneousheterogeneous

Examples elements compounds homo mix hetero mix Carbon waterairconcrete Carbon waterairconcrete Iron carbon dioxidesalt watermilk Iron carbon dioxidesalt watermilk Gold table salt (NaCl)white goldwood Gold table salt (NaCl)white goldwood Mercury aspirinbrasssand Mercury aspirinbrasssand

Solutions Solutions are homogeneous mixtures. A solute (the dissolved substance) is put in a solvent (the dissolving substance). The solvent is the substance there is more of.

Physical Changes - are those in which the identifying properties of a substance are unchanged - Ex. : change of phase breaking, cutting breaking, cutting dissolving dissolving

Chemical Changes - are those in which different substances are formed - Ex.: burning rusting rusting decaying or spoiling decaying or spoiling acid reacting with metal acid reacting with metal

Signs of a chemical change Heat gained or lost Heat gained or lost Production of a gas Production of a gas Formation of a precipitate Formation of a precipitate Color change Color change

Law of Conservation of Mass During a chemical reaction, the mass of the products always equals the mass of the reactants. During a chemical reaction, the mass of the products always equals the mass of the reactants.

Methods of separating a mixture Use the different properties of the substances to separate them. Sand and iron filings Sand and iron filings Sand and salt Sand and salt Sand in water Sand in water Water from salt water Water from salt water Oil in water (immiscible liquids) Oil in water (immiscible liquids) Mixture of pigments Mixture of pigments filter Dissolve salt, evaporate water Remove iron with magnet Distill the water Settle and extract less dense liquid Paper chromatography

chromatography distillation

Chemical symbols First letter is always capitalized. First letter is always capitalized. Second letter, if there is one, is never capitalized. Second letter, if there is one, is never capitalized. Co and CO are very different! Co and CO are very different! Some elements use the Latin name Some elements use the Latin name 2O means 2 oxygen atoms 2O means 2 oxygen atoms O 2 means two oxygen atoms are O 2 means two oxygen atoms are chemically bonded together. chemically bonded together.

Substance – a homogeneous material consisting of one kind of matter Substance – a homogeneous material consisting of one kind of matter Compound – a substance that can be decomposed into simpler substances by chemical means Compound – a substance that can be decomposed into simpler substances by chemical means Element – substances that cannot be further broken down. Element – substances that cannot be further broken down.