Unit 1Classifying

Matter Notes

Flow chart

Pure Substances (elements and compounds)

1. EVERY SAMPLE of a given pure substance has EXACTLY THE SAME characteristic properties.

a. Boiling point

b. Freezing point

c. Melting point

d. Density

2. Can NOT BE SEPARATED by PHYSICAL means

 

Ex: water always has a boiling point of 100 C, melting point of 0 C, freezing point of 0 C and a density of l.00 g/ml. Other pure substances have their own individual characteristics (bp, mp, fp, density)

Elementcomposed of identical atoms

– EX: copper wire and aluminum foil

Examples of Pure Substances continued...

Compound– composed of 2 or more elements

in a fixed ratio

– properties differ from those of individual elements

– EX: table salt (NaCl)

Pure Substances

Law of Definite CompositionLaw of Definite Composition

– A given compound always contains the same, fixed ratio of elements.

Law of Multiple ProportionsLaw of Multiple Proportions

– Elements can combine in different ratios to form different compounds.

2 kinds of mixtures

Mixture –

1. Not the same as a compound. Usually composed of several substances.

2. CAN be separated by PHYSICAL means

• Variable composition

• Components retain their characteristic properties

• May be separated into pure substances by physical methods

• Mixtures of different compositions may have widely different properties

1.Homogeneous mixtures

– also called solutions

have the same

composition throughout.

Ex: salt water

Types of Mixtures

Solution– homogeneous

– very small particles

– no Tyndall effect Tyndall Effect

– particles don’t settle

– EX: rubbing alcohol

How Solutions are Made…

Colloids are solutions. They can be described as a substance trapped inside another substance. They can be identified by their ability to scatter light, Tyndall Effect.

For example: air trapped inside the fat molecules in whipped cream.

Types of Mixtures continued…

Colloid– heterogeneous– medium-sized particles– Tyndall effect– particles don’t settle– EX: milk

2. Heterogeneous mixtures – the composition is NOT the same throughout; Ex: blue cheese dressing, sand and water, trail mix

Types of Mixtures continued…

Variable combination of 2 or more pure substances.

Heterogeneous Homogeneous

Learning Check

Learning Check: Identify the following as pure substances (p) or mixtures (m):

___ Oxygen (O2) ___ Lemonade ___ Snickers bar___ Distilled water ___ Dry ice ___ Soil

P

M

M

P

P

M

Learning Check

Learning Check: Classify the following as Homogeneous (ho) or Heterogenous mixtures (he)

___ Pure Air ___ Salsa ___ Chocolate chunk ice cream ___ Ink ___ Blood ___ Chicken noodle soup

HoHe HeHoHoHe

Physical Separation:Separates MIXTURES

1.Distillation – based on differences in boiling point: separating a mixture of alcohol and water. Alcohol has a lower boiling point than

water so it will boil off sooner. Both

substances will be retained

2.Filtration – based on

differences in solubility

and particle size

-liquid is passed through

materials with very small

holes to strain out particles.

Physical Separation:Separates MIXTURES

3.Chromatography

– based on differences

in polarity

Example Video

Physical Separation:Separates MIXTURES

4.Magnetism – separating iron and sand

Physical Separation:Separates MIXTURES

Chemical Separation: Separates COMPOUNDS

Electrolysis – a method of separating compounds (pure substances). This is NOT a physical separation, but a chemical separation using electricity.

Waterhydrogen + oxygen

Learning Check

Which method would be appropriate for separating these mixtures?

 

_______________ Sawdust and water

_______________ Nails and dirt

_______________ Water and vinegar

Filtration

Magnetism

Distillation

Classification of Matter

Materials

HomogeneousHeterogeneous

Heterogeneousmixture

Homogeneousmixture

Substance

Element Compound Solution Mixture

Order / Disorder

Reviewing ConceptsClassifying Matter

• Why does every sample of a given substance have the same properties?

• Explain why the composition of an element is fixed.

• Describe the composition of a compound.

• Why can the properties of a mixture vary?

• On what basis can mixtures be classified as solutions, suspensions, or colloids?