topic: classifying matter

Topic: Classifying Matter

Indicate whether the following changes are physical or chemical. • Burning wood• Tearing paper• Freezing Water• Dissolving NaCl in H2O• Mixing NaCl and SiO2

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

Atoms

Pure Substance

• 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

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 different types of

atoms chemically combined in a definite ratio

• Properties are different from those of elements formed from

• Only Broken into elements by chemical rxn

• Formulas have 2 or more uppercase letters

H

H HO

H

HCl

Cl

Cl

H HO

HCl

H2O

2Na + Cl2 2NaCl

Element or Compound?

Na = element

Cl2 = element

NaCl = compound

Particle DiagramsAtoms of a diatomic (2) compounds

Molecules: Can be elements or compounds – but must contain 2 or more total atoms (can be the

same type or different)

O O

H H

OS S S S

HCl

S S S S

O2

H2O

S8

HCl

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: NOT UNIFORM

throughout -individual components visible - scatters light (can’t shine light through)

GraniteOil in water Salad

dressing

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): UNIFORM composition throughout- individual components not visible

• Solutions in gas & liquid phases transmit light (can shine light

through)• 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?