Chem 11

Indications of a chemical reaction

• Energy absorbed or released

• Color change

• Gas produced

• Precipitate- solid that separates from solution

• Not easily reversed

• ALWAYS THERE IS A NEW SUBSTANCE!

Pure substance:

• contains one type of particle.– Elements:– Compounds:

Mixture:

• contains two or more types of particles intermingling, no chemical bonding.– Homogeneous:– Heterogeneous:

• Composed of two or more different atoms

• Can be broken down by chemical methods and each part will have different properties

• Examples: water (H2O), 2 atoms of hydrogen, 1 atom of oxygen)salt (NaCl), 1 atom of sodium, 1 atom of chlorine

• An element is a substance made up of only one kind of atom

• The periodic table arranges elements according to their properties

One kind of matter-Molecule or atom

More than one kind of matter- different molecules or atoms

Made during a

chemical change Made through a

physical change

Definite and uniform composition

Variable in composition

Which is it?

ElementCompoundMixture

• has parts with different properties (composition is not uniform)

• Different kinds of particles stay together.

• Mechanical mixing• Ex: sand and salt,

blood, milk, pizza, sand, salad

• Looks the same throughout (uniform composition)

• Particles are intermingled• May be solutions

(something dissolved)• Ex: air, salt water, silver,

sugar, salt

• Homogeneous mixture with molecules mixed uniformly

• Solutions occur between any state of matter.Examples: Solid in liquid- Kool-aid

Liquid in liquid- antifreeze

Gas in a liquid – carbonated beverages

Gas in gas- air

Solid in solid - brass

Liquid in gas- water vapor

• Like all mixtures, the components keep their own properties.

• Components can be separated by physical means

They cannot be separated physically!!

…… but mixtures can!

• Examples of physical separation:

magnetic

boiling points-distillation

filtration

SEPARATION OF A HETEROGENEOUS MIXTURE

Separation based on physical method. Magnetic property of the iron.

MIXTURES

• MAY BE HOMOGENEOUS OR HETEROGENEOUS

• EACH COMPONENT KEEPS ITS IDENTITY

• CAN BE PHYSICALLY SEPARATED

• THE COMPONENTS CAN BE COMBINED IN MANY PROPORTIONS

Classification of Matter