Topic: Classifying Matter Which of the following is a physical change that requires energy? H2O (l)  H2(g) + O2 (g) H2O (l)  H2O (s) H2O (s)  H2O (l) H2(g) + O2 (g)  H2O (l)

Matter Substances Mixtures Mixtures  Separated by physical methods Elements Compounds Heterogeneous Homogeneous Can it be separated by physical methods NO YES Mixtures  Separated by physical methods Compounds  Separated by chemical methods

Pure Substance Homogenous (uniform throughout) Definite composition Same characteristic properties regardless of source which are pure substances

Element Substance that: Formulas have 1 uppercase letter cannot be broken down or decomposed into simpler substance only 1 kind of atom has definite properties Formulas have 1 uppercase letter Cu Cu Cu Cu F2 F F F F

Atom smallest particle of element that retains properties of element & can undergo a chemical rxn Atoms can be combined to form molecules =2 or more total atoms F F F F

        Particle Diagrams Atoms of a monatomic (1) element         Molecules of a diatomic (2) element        

These seven elements are always diatomic F F2 Cl2 Cl Br2 Br I2 I

Element Song Big Bang Version sung by Sheldon

Compounds 2 or more elements chemically combined in a definite ratio Properties are different from those of elements formed from Only Broken into elements by chemical decomposition reaction Formulas have 2 or more uppercase letters HCl Cl H H Cl Cl H H2O O H H O H H

2Na + Cl2  2NaCl Na = atom, element Cl2 = molecule, element NaCl = molecule, compound Atoms or Molecules? Element or Compound?

         Particle Diagrams Molecules of a triatomic (3) compound          Mixture: monatomic element, diatomic element, triatomic compound             

Made of Ions Na+1Cl-1 = NaCl

Mixtures Combo of 2 or more pure substances (elements + elements) (elements + compounds) (compounds + compounds) Physically combined not chemically combined Each substance retains its own identity and properties

Mixtures Variable composition No unique properties (Think of sugar and salt mixed together) Separated by physical methods May be homogeneous or heterogeneous

Types of Mixtures Heterogeneous: definite variation in composition, individual components visible - scatters light (can’t shine light through) Oil in water Salad dressing Granite

Colloids (type of heterogeneous mix.) Particles are suspended- they are too small to see Aerosols: solid or liquid particles in gas Ex: Smoke/Fog: solid in a gas Gas in liquid: Ex: whipped cream Emulsion: liquid in liquid Ex: mayonnaise (oil suspended in water – use egg yolk to Sols: solid particles in a liquid Ex: Milk of Magnesia (solid magnesium hydroxide in water) Gels: Liquid in solid Ex: Quicksand: sand in water

Suspensions (type of heterogeneous mix.) Particles are larger can be evenly distributed by mechanical means (shaking the contents) Settle out on standing

Solutions in gas & liquid phases transmit light Homogeneous (aka solutions): constant composition throughout, individual components not visible Solutions in gas & liquid phases transmit light particles not big enough to scatter light look translucent

RECAP: Solution vs Suspension Solutions in gas & liquid phases transmit light particles not big enough to scatter light look translucent Suspensions look cloudy particles big enough to scatter light settle on standing

Solution(homogenous) vs Suspension(heterogeneous)

Solution(homogenous) vs Suspension(heterogeneous) CuSO4(aq) Solution(homogenous) vs Suspension(heterogeneous)

Heterogeneous Mixture: elements & elements O2 in the gas phase Or Homogeneous? Compounds? Elements? Solid? Liquid? Gas? Homogenous Mixture: Compounds & elements Both in liquid phase O H H O H H O H H O H O F- H H F- O F- H H F- O H F- O F- O H F- H H H H F- O O O Heterogeneous Mixture: elements & elements O2 in the gas phase K in the solid phase O O O K K K K K K O O