topic: classifying matter

Topic: Classifying Matter

Which of the following is a physical change that requires energy?

a) H2O (l) H2(g) + O2 (g)b) H2O (l) H2O (s)c) H2O (s) H2O (l)

d) H2(g) + O2 (g) H2O (l)

Matter

Substances Mixtures

Elements Compounds HeterogeneousMixtures

HomogeneousMixtures

Mixtures Separated by physical methodsCompounds Separated by chemical methods

Can it be separated by physical methods

NO YES

Pure Substance

• Homogenous (uniform throughout)• Definite composition• Same characteristic properties regardless of

source which are pure substances

Element• Substance that:

• cannot be broken down or decomposed into simpler substance

• only 1 kind of atom• has definite properties

• Formulas have 1 uppercase letter

Cu

F F FF

Cu

Cu

Cu

F2

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

FF

FF

Particle Diagrams

Atoms of a monatomic (1) element

Molecules of a diatomic (2) element

I

N O F

Cl

Br

These seven elements are always diatomic HH2

N2 O2 F2

Cl2

Br2

I2

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

H

H HO

H

HCl

Cl

Cl

H HO

HCl

H2O

2Na + Cl2 2NaCl

Atoms or Molecules?

Element or Compound?

Na = atom, element

Cl2 = molecule, element

NaCl = molecule, compound

Particle Diagrams

Molecules of a triatomic (3) compound

Mixture: monatomic element, diatomic element, triatomic compound

Made of IonsNa+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)

GraniteOil in water Salad

dressing

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

toSols: 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

• 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)

CuSO4(aq)

Solution(homogenous) vs Suspension(heterogeneous)

K

O

H

KKK

K

O

O O

K

HO

H HO

H HO

H HO

H HO

H HO

H HO

H HO

HO

F- F

-

F-

F-

F-

F-

F-

F-

O O

O O

Homogenous Mixture:Compounds & elementsBoth in liquid phase

Heterogeneous Mixture:elements & elementsO2 in the gas phaseK in the solid phase

Heterogeneous?

Or

Homogeneous?

Compounds?

Or

Elements?

Solid?Liquid?

Gas?