Classification of Matter

Chapter 2

Objectives

LWBAT:

1.Describe the characteristics of physical and chemical properties.

2.Classify mixtures as homogenous or heterogeneous.

3.Describe the characteristics of physical and chemical changes.

What is matter?

Matter is anything that has mass and takes up space.

MaterialsSpecific types of matter

Described according to phases (solid, liquid, gas)

Pure SubstancesContain only one type of matterCannot be separated physicallyHas a fixed composition (structure)

Pure Substances

Elements - simplest pure substances made of only one type of atom (Periodic Table)Cannot be broken down into a simpler substances.

Pure Substances

Compounds - – two or more elements chemically combined (H2O, CuSO4)

Always in a fixed proportion (relationship)

MixturesPhysical combination of two or more substances

Can be separated physically

Heterogeneous MixturesPrefix “Hetero-” means differentSubstances can be easily distinguished and separated

Ex: sand and salt, trail mix, sand and gravel, salad

Homogeneous Mixtures

Prefix “Homo-” means same

Substances are well mixed and appear the same throughout

Ex: Solution

SolutionsSolute dissolves in solvent to form solution.

(solute + solvent = solution)Concentrated solution contains more solute than dilute solution.

Ex: Kool-Aid, iced tea, coffee

Physical Properties(appearance changes but materials

stays the same)

Describe substances undergoing physical changes

Ex: viscosity, conductivity, malleability, hardness, density, boiling point and melting point

ViscosityThe tendency of a liquid to keep from flowing—its resistance to flowing. Example:

Honey – high viscosity Vinegar – low viscosity

Conductivity

A material’s ability to allow heat to flow

High conductivity – metal spoon Low conductivity – wooden spoon

Malleability

Ability of a solid to be hammered without shattering

Hardness

One way to compare the hardness of two materials is to see which of the materials can scratch the other.

DensityCan be used to test the purity of a substanceFormula: mass/volume

Example: testing fuel in motorcycles

Melting and Boiling Points

Melting point – temperature at which a substance changes from a solid to a liquidBoiling point – temperature in which a substance boils (liquid to a gas)

Additional Physical Properties

Color Shape (structure)Texture (how the material feels)

Using Properties to Separate Mixtures

Filtration – a process that separates materials based on the size of the particles.Distillation – a process that separates the substances in a solution based on their boiling point.

Chemical Properties

Describe substances undergoing chemical changes

Ex: flammability, reactivity

Flammability

A material’s ability to burn in the presence of oxygen.

Reactivity

The property that describes how a substance combines chemically with other substances; forms a new substance

Iron + water = rust

Is it a chemical or physical change?

When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.

Law of Conservation of Matter

Matter is not created or destroyed during a physical or chemical change

Physical Change Chemical Change

Physical ChangesSame substance remains after changeUsed to separate mixtures

Ex: pounding, tearing, cutting, dissolving, evaporating, melting, boiling, pulling

Chemical ChangesResults in new substance with new propertiesAlso known as a chemical reaction

Ex: burning, digesting, fermenting, decomposing

Chemical Change Evidence1. Precipitate forms (solid)2. Gas evolves (bubbles)3. Color change (tarnishing)4. Energy change

•Exothermic = releases energy•Endothermic = absorbs energy

5. Odor produced (sometimes)