Chapter 18Chapter 1818.1 18.1 –– Composition of Matter Composition of Matter

ObjectivesObjectives

Define pure substances and mixtures.Define pure substances and mixtures. Identify elements and compounds.Identify elements and compounds. Compare and contrast solutions, colloids, Compare and contrast solutions, colloids,

and suspensions.and suspensions.

Pure SubstancesPure Substances

Type of matter with a fixed compositionType of matter with a fixed composition Can be element or compoundCan be element or compound

Element = pure substance in which all Element = pure substance in which all atoms have the same identityatoms have the same identity 90 elements found on Earth90 elements found on Earth 20+ have been made in labs20+ have been made in labs

Most are unstable and exist for a short period of Most are unstable and exist for a short period of timetime

Pure substancePure substance

Compounds = when 2 or Compounds = when 2 or more different elements more different elements combine in a fixed combine in a fixed proportionproportion Water, Table Salt (NaCl)Water, Table Salt (NaCl)

Molecules = particle Molecules = particle consisting of 2 or more consisting of 2 or more atoms bound togetheratoms bound together

MixturesMixtures

Material made up of 2 or more substances Material made up of 2 or more substances that can be easily separated by physical that can be easily separated by physical meansmeans

Heterogeneous mixtures = mixture in Heterogeneous mixtures = mixture in which different materials can be easily which different materials can be easily distinguisheddistinguished Granite, Concrete, Pasta Salad, ClothingGranite, Concrete, Pasta Salad, Clothing

MixturesMixtures

Homogeneous mixture = 2 or more Homogeneous mixture = 2 or more substances blended evenly throughoutsubstances blended evenly throughout Soft drinks, Pudding, VinegarSoft drinks, Pudding, Vinegar

Solution = particles so small that they Solution = particles so small that they cannot be seen with microscope and will cannot be seen with microscope and will never settle to the bottom of their never settle to the bottom of their containercontainer

ColloidsColloids

Mixture with particles that are larger than Mixture with particles that are larger than those in solutions but not heavy enough to those in solutions but not heavy enough to settle outsettle out

Greek word for Greek word for ““glueglue”” Examples: Milk, GelatinExamples: Milk, Gelatin

Detecting ColloidsDetecting Colloids

Pass light beams throughPass light beams through Solutions = no light comes throughSolutions = no light comes through Colloids = light readily passes throughColloids = light readily passes through

Tyndall Effect = scattering of light by Tyndall Effect = scattering of light by colloidal particlescolloidal particles

SuspensionsSuspensions

Heterogeneous mixture containing liquid in Heterogeneous mixture containing liquid in which particles settlewhich particles settle

Example: Pond WaterExample: Pond Water

In-Class Assignment/HomeworkIn-Class Assignment/Homework

18.1 Reinforcement & Enrichment WKT18.1 Reinforcement & Enrichment WKT Reinforcement #10-15 use p. 553Reinforcement #10-15 use p. 553 Enrichment – complete like examplesEnrichment – complete like examples

Pond Water = Mixture Pond Water = Mixture heterogeneous heterogeneous suspensionsuspension

Potassium fluoride = substance Potassium fluoride = substance compound compound Carbon = Substance Carbon = Substance element element