Pure SubstanceMatter that always has exactly the samecomposition is classiﬁed as a pure substance*every sample of a given substance has thesame properties because a substance has aﬁxed, uniform compositioncan be classiﬁed into two categories-elementsand compounds
Elements and Atomsa substance that cannot be broken down into simplersubstancesan atom is the smallest particle of an element*an element has a ﬁxed composition because itcontains only one type of atomno two elements contain the same type of atom
Compounds a substance that is made from two or moresimpler substances and can be broken downinto those simpler substancesThe simpler substances are either elements orother compounds
Mixture*the properties of a mixture can vary becausethe composition of a mixture is not ﬁxedmixtures can be classiﬁed by how well theparts of the mixture are distributed throughoutthe mixture
Heterogeneous and homogenous mixturesHeterogeneous: the parts of a mixture arenoticeably different from one another (sand)Homogenous: the substances are so evenlydistributed that it is difﬁcult to distinguish onesubstance from another(serving spoon-iron,chromium, and nickel)
Solutions/Suspensions/Colloids *Based on the size of its largest particles, a mixture can be classiﬁed as a solution, suspension, or colloid Solution: when substances dissolve and form a homogenous mixture Able to see through solutions that are liquids because light passes through them without going in all different directions Suspension: heterogeneous mixture that separates into layers over time
Physical PropertiesAny characteristic of a material that can be observedor measured without changing the composition of thesubstances in the materialUsed to identify a material, to choose a material for aspeciﬁc purpose, or to separate the substances in amixtureviscosity, conductivity, malleability, hardness, meltingpoint, boiling point, and density are all
ViscosityThe tendency of a liquid to keep fromﬂowing, it’s resistance to ﬂowingHoney has a high viscosity because it isvery resistant but water has a lowviscosity because it is not very resistant
ConductivityA material’s ability to allow heat to ﬂowwould you use a metal or woodenspoon while stirring soup?A wooden one because it has lowconductivity so the top of the spoondoesn’t get hot and it won’t burn you
MalleabilityThe ability of a solid to be hammeredwithout shatteringGold is malleable because whenhammered, it doesn’t shatter but an icecube is not because if hammered, itwould shatterMost metals are malleable
Melting pointTemperature at which a substance changesfrom a solid to a liquidMelting point for water is 0˚c at sea level
Boiling PointTemperature at which a substance boilsBoiling point for water is 100˚c at sea level
DensityUsed to test the purity of a substanceRatio of the mass of a substance to its volume
Identifying a Material1. Decide which properties to test2. Do tests on the sample of the unknown3. Compare the results with the data reportedfor known materials
What are Properties?They determine which materials are chosen forwhat uses
Filtration and DistillationThese two terms are common separationmethodsFiltration: a process that separates materialsbased on the size of their particlesDistillation: a process that separates thesubstances in a solution based on their boilingpoints
What is physical change?The change of water from a liquid to a gasduring boilingThis occurs when some of the properties of thematerial change but the substances in thematerial stay the same
Ways of Separating a MixtureDistillationFiltrationEvaporation
Distillation A process that separates two substances in a solution based on their boiling points Distillation ApparatusUnknown SubstanceAlcohol Burner
FiltrationA process that separates materials based on thesize of particles +/or solubilityﬁlter paper goes inside ﬁlterthe mixture is poured into ﬁlter paperthe element left in the ﬁlter paper is thesubstance and the liquid at the bottom is topuriﬁed water (liquid)
EvaporationA process used to isolate a solid dissolved in aliquidex: NaCl+waterDisclaimer: water(liquid) will evaporate+youwon’t be able to isolate a sample of itmixture is poured into an evaporating dishwhich is heated and all that is left is thedissolved element that is now not dissolved
Chemical PropertyAny ability to produce a change incomposition of matterChanges the composition of the substance*Chemical properties can only be observedwhen the substances in a sample of matter arechanging into different substances
FlammabilityA material’s ability to burn in the presence ofoxygenExample: alcohol and water
ReactivityA property that describes how readily asubstance combines with other substances.Example: Oxygen/Potassium
Chemical ChangeOccurs when a substance reacts and forms oneor more new substances*Three common types of of a chemical change:-change in color -the production of gas -theformation of a precipitate
PrecipitateAny solid that forms and separates from aliquid mixture
#1 QUESTIONHOW MANY CATEGORIES ARE PURESUBSTANCES CLASSIFIED INTO? ANDWHAT ARE THOSE CATEGORIES?
#2 QUESTIONWHAT TYPE OF CHANGE DO YOU USEWHEN YOU WANT THE COMPOSITION OFTHE SUBSTANCES TO STAY THE SAME?
#3 QUESTIONWHAT TECHNIQUE WOULD YOU USE TOISOLATE A SOLUTION OF SALT ANDWATER?
#4 QUESTIONIF BLUE DYE WAS SPILLED ON A SHIRT,WOULD IT BE A CHEMICAL OR PHYSICALCHANGE? WHY?
ANSWERS:#1- Pure substances are classiﬁed into two categories,elements and compounds.#2-You would use a physical change if you wanted thecomposition of the substances to stay the same.#3-The technique used to isolate a solution of salt andwater would be evaporation.#4-It would be a chemical change if blue dye wasspilled on a shirt because it changes the color, but also,it can never come out therefore it adds to the object.