Chemistry - the study of matterMatter is anything that has mass and occupies spacePhysical States of MatterOxygen and nitrogen can be liquidsIron can be vaporizedThe state of matter observed for a substance is dependent on the temp. and pressure→Matter can exist in all three statesChapter 3: Matter and Energy Ch 3 Page 1Pure substance: a form of matter composedof a single chemical - either an element or acompound.Element - a pure substance composed of just Elements CAN NOT be broken down into simpler substances by ordinary chemical means.one type of atom. Compounds - a pure substance composed of more than one type of atom with the atoms present in fixed ratios.Ex. In all samples of pure water there are 2 hydrogen atoms for every oxygen atom: H2OA compound CAN be brokendown into 2 or more simplersubstances by chemical means.Ex. Electrolysis of Water 2 H2O 2 H2 + O2Elements and Compounds Ch 3 Page 2A MIXTURE is a physical combination of 2 or Types of Mixturesmore substances. The composition of a mixture can vary from sample to sample and its components can be separated by physical means.A pure substance always has a definite and constant composition. HeterogeneousContains visibly different parts or phases, each of which has different properties.HomogeneousContains only one physicallydistinct phase which has uniform properties throughout - a SOLUTIONPure Substances and Mixtures Ch 3 Page 3Classify the following as a pure substance or a homogeneous or heterogeneous mixturea cup of coffee b) 24 carat gold bar c) green painta)chocolate chip cookie e) Kool Aid f) mercury d)Physical and Chemical Properties and Changesa) odor and colorboiling point and melting pointc)how they react with other chemicals, etc..d)b) densityWe recognize various chemicals by:Physical Properties can be observed without changing a substance into another substanceChemical Properties are properties that matter exhibits as it undergoes changes inchemical compositionA chemical property of iron is that it reacts with oxygen 2 Fe + 3 O2 2 Fe2O3to form iron(III) oxide - RUST! burn)The failure of a substance to react is also considered a chemical property: CCl4+ O2 NO RXN (does notPhysical and Chemical Properties Ch 3 Page 4Physical change is a process that does NOT alter the basic nature (chemical composition) of a substance but only changes the form or appearance of the substance. (A new substance is not formed, only its state has changed).Phase changes are physical changes (between solid, liquid, and gas) (Water Vapor or Steam) Solid ice Liquid Water Gaseous Waterie pulverizing an aspirin tearing paper into smaller piecesChanges in size and shape are physical changes Filtration, distillation, and other methods of separating mixtures into pure substances are physical changes.Dissolving one substance into another is a physical change Types of Physical ChangesPhysical Change Ch 3 Page 5Chemical change:A new type of matter is formed•A new chemical formula is written•Also known as a chemical reaction•Color changeOdor, gas evolved (but not just from boiling)Flame, burningTemperature change on its ownClues that a chemical change has occurred (all of these are evidence that a new substance has formed) C4H10 + O2 CO2 + H2O(butane)Water evaporatinga)Smoking a cigaretteb)Dissolving salt in waterc)Crushing a piece of charcoald)Gasoline being used in your car enginee)Boiling an egg (cooking it)f)Boiling waterg)Classify these as physical or chemical changes:A Chemical equation represents a chemical reactionReactant(s)Product(s)chemicalreactionChemical Change Ch 3 Page 6In any chemical reaction mass is neither created nor destroyed. ORThe products of a chemical reaction have the same total mass as the reactantsBehavior of matter is driven by energy, so understanding energy is critical in the study of chemistryEnergy can not be created nor destroyedLaw of the Conservation of EnergyCommon forms of energy heat, light, electrical, mechanical and chemical energyHowever, we can transfer energy from one place to another and we can change its formENERGYHydroelectric DamTypes of EnergyKinetic Energy: energy of motion(translational,rotational,vibrational)Potential Energy: stored energy an object possesses due to its position or chemical compositionLaw of the Conservation of Mass Ch 3 Page 7Common Energy UnitsSI Unit = Joule (J)calorie (cal)= amt of energy required to raise one gram of water by 1oCCalorie (food calorie) = 1000 cal1 cal = 4.184 JIn most chemical reactions the chemical potential energy of the products is LOWER than that of the reactantsPotentialEnergyReactantsProductsDuring such a chemical change energy is released. If the energy released isheat energy, the reaction is said to be EXOTHERMICIf heat energy is absorbed during a chemical change the reaction is said to be ENDOTHERMICA: In an exothermic chemical reaction the energy released was originally stored as potential energy in the chemical bonds of the reactants. Consequently, during that reaction the total energy does not change but a transformation between forms of energy occurs - the stored potential energy is converted to heat (or other forms of energy).Q: If energy is released during an exothermic chemical reaction, don't we lose energy?Energy Ch 3 Page 8- as temp decreases, molecular motion __________Temperature is a measure of atomic or molecular motion - as temp increases, molecular motion___________ Temperature ScalesFahrenheit scale (oF) - used in the U.S.Celcius scale (oC)- used in the rest of the world and in scienceKelvin scale (K) - SI Unit; used in scientific calculations - the absolute scale ("Absolute zero")Temperature Ch 3 Page 9K = °C + 273.15 °F = °C + 32 or °C = (°F - 32)955947.0 °C = ? K 68 °F = ? °C68 °F = ? KTemperature Conversions Ch 3 Page