Chapter 2 Properties of Matter Chemistry 1

Classifying Matter 2.1

Pure Substances 2.1 Matter that always has exactly the same compositionMatter that always has exactly the same composition Every sample the same b/c substance has a fixed, uniform compositionEvery sample the same b/c substance has a fixed, uniform composition 2 categories2 categories 1.Element – Ex: Iron, Copper, Carbon 2.Compound – Ex: Water, Sugar, Table Salt

Elements 2.1 Substance that can’t be broken down into a simpler substanceSubstance that can’t be broken down into a simpler substance Only contains 1 type of atomOnly contains 1 type of atom Atom – smallest particle of an elementAtom – smallest particle of an element Room temp (68 o F) = most elements are solidRoom temp (68 o F) = most elements are solid Jons Berzelius – started system for symbols of elementsJons Berzelius – started system for symbols of elements –1 or 2 letters (1 st capitalized, 2 nd lowercase) –Based on Latin names

Compounds 2.1 Substance made of 2 or more elements in a fixed proportionSubstance made of 2 or more elements in a fixed proportion Can be broken down into simpler substancesCan be broken down into simpler substances Compound properties different than elements’ properties that make up compoundCompound properties different than elements’ properties that make up compound

Mixtures 2.1 Properties can vary b/c composition is not fixedProperties can vary b/c composition is not fixed Tend to retain properties of individual substanceTend to retain properties of individual substance HETEROGENEOUS MIXTUREHETEROGENEOUS MIXTURE –“different kind” –Parts are noticeable different –Ex: mixed nuts HOMOGENEOUS MIXTURE HOMOGENEOUS MIXTURE –Substances are so evenly distributed that it is difficult to distinguish one substance from another –Ex: stainless steel = iron + chromium + nickel

Solution – homogenous mixtureSolution – homogenous mixture 1.Liquids do not separate into layers over time 2.If poured thru a filter, substances are not trapped 3.Can see thru b/c light passes without being scattered in all directions –Very Small particles Suspensions – heterogeneous mixtureSuspensions – heterogeneous mixture –“shake well before use” 1.Separate into layers 2.Trapped by a filter 3.Can scatter light in all directions = cloudy –Large particles ColloidColloid –Contains intermediate particles 1.Do not separate into layers 2.Cannot use a filter to separate 3.Scattering of light –Examples: milk and fog

Physical Properties 2.2

Characteristic of a material that can be observed or measured without changing compositionCharacteristic of a material that can be observed or measured without changing composition Viscosity, conductivity, malleability, hardness, melting point, boiling point, densityViscosity, conductivity, malleability, hardness, melting point, boiling point, density ViscosityViscosity –its resistance to flow –The higher the viscosity, the slower the substance flows –Usually decreases when heated ConductivityConductivity –Ability for heat flow –High conductivity = good conductor  metals If good conductor of heat, normally good conductor of electricityIf good conductor of heat, normally good conductor of electricity

MalleabilityMalleability –Ability of a solid to be hammered without shattering –Most metals are malleable –Solids that shatter = brittle HardnessHardness –See what materials scratch the other –Diamond = hardness known material –What do you use to sharpen a knife? Melting/Boiling PointMelting/Boiling Point –Melting Point – Substance changes from a solid to a liquid Water = 0 o CWater = 0 o C –Boiling Point – Substance boils Water = 100 o CWater = 100 o C

DensityDensity –Can be used to test purity Test purity of methanol (fuel)Test purity of methanol (fuel) –d = m/v

Using Physical Properties 2.2 Identifying MaterialIdentifying Material 1.Decide which properties to test 2.Run tests on sample of unknown 3.Compare with previous data reported –Choose Materials –Wouldn’t want a shoelace from wood (must be flexible and durable)

Using Properties to Separate Mixtures 2.2 Filtration – process that separates materials based on the size of their particlesFiltration – process that separates materials based on the size of their particles –Small particles can pass thru a strainer –Ex: brewing coffee Distillation – process that separates the substance in a solution based on their boiling pointsDistillation – process that separates the substance in a solution based on their boiling points –Ex: fresh water for a submarine Subs can only hold water for about 10 day  convert seawater to fresh waterSubs can only hold water for about 10 day  convert seawater to fresh water

Recognizing Physical Changes 2.2 Occurs when some of the properties of a material change but the substance remains the sameOccurs when some of the properties of a material change but the substance remains the same –Ex: phase changes –Cutting –Crumpling –Some can be reversed, some can not

Chemical Properties 2.3

Observing Chemical Properties 2.3 Ability to produce a change in the composition of matterAbility to produce a change in the composition of matter Can only be observed when sample is changing to a different substanceCan only be observed when sample is changing to a different substance Ex: Candles BurningEx: Candles Burning –Candle = made of paraffin = made of C & H When candle burns, C combines with air to from Carbon Dioxide and H combines with the air to form water.When candle burns, C combines with air to from Carbon Dioxide and H combines with the air to form water.

Chemical Properties 2.3 FlammabilityFlammability –Materials ability to burn in the presence of oxygen Ex: paper and gasolineEx: paper and gasoline ReactivityReactivity –How readily a substance combines chemically with other substance Ex: N – extremely low reactivityEx: N – extremely low reactivity Ex: O – highly reactive element (rust)Ex: O – highly reactive element (rust)

Recognizing Chemical Changes 2.3 Substance reacts and forms one or more new substancesSubstance reacts and forms one or more new substances Change in ColorChange in Color –Jewelry darkens –Matches turn black –Roofs –Rust Production of GasProduction of Gas –Mix vinegar with baking soda = bubbles of carbon dioxide –Baking powder + acid in a cake recipe = bubbles of carbon dioxide Formation of a PrecipitateFormation of a Precipitate –Formation of any solid that separates from a liquid mixture –Curdling of milk

Is a Change Chemical or Physical? Can not be POSITIVE a chemical change has occurred when you see bubbles, color change, or precipitateCan not be POSITIVE a chemical change has occurred when you see bubbles, color change, or precipitate –Ex: water boiling = physical change –Iron heated = gray  red = physical change Ask: are different substances present after the change?Ask: are different substances present after the change? –Chemical Change = Composition of matter changes –Physical Change = Composition of matter is the same