Chapter 2

Objectives > Explain the relationship between matter,

atoms, and elements. > Distinguish between elements and

compounds. > Describe molecules, and explain how they

are formed. > Interpret and write some common

chemical formulas. > Categorize materials as pure substances

or mixtures.

Matter

Composed of mass Takes up space Everything is made of

matter Pie charts in book

A classification scheme for matter.

Classifying matter Pure substance

ElementsCompounds

MixturesHomogeneousHeterogeneous

Pure substances Definite chemical

composition- ratio does not change

Can not be seperated

Elements Makes up Matter Substances that cannot be

broken down into simpler substances

Atoms Smallest unit of an element

that has the properties of an element

Smallest particle of element

Atomos=no division

Molecule The joining of atoms to

form the smallest unit of a substance that has all the properties of that substance

Acts as a unit

Compound Atoms of 2 or more

elements that chemically combine to form new substances

Has different properties than the elements in it

Compound cont’d When elements combine or

come together to form a specific compound like H2O they always combine in the same proportions

2 Hydrogen's for 1 Oxygen

Diatomic elements Atoms of the same element

that combine to form a molecule because they are unable to stand alone

Ex. O, H, Cl, P

Chemical Formulas Represent compounds and

formulas in a short hand way. All chemicals have a symbol it

is 1 or 2 letters

Chem. form. Con’t

The first letter in a symbol is always capitalized and the second, if needed, is always in lowercase.

Formulas show how many atoms of each chemical is used

Chem. form. Cont’d

This number is called a subscript and is smaller and located to the right of the chemical symbol it goes with, ie H2O- the 2 is the subscript for 2 hydrogens.

Chemical formulasChemical formulas 1C16H10N2O2 One molecule of indigo

ink contain 16 carbon, 10 hydrogen, 2 nitrogen and 2 oxygen

Mixtures

Combination of pure substances that are not chemically combined

Mixtures There are 2 types of

mixturesHomogeneousHeterogeneous

Homogeneous Mixture is the same

throughout example- Ketchup

Solutions are homogeneous

Heterogeneous

Not mixed evenly example chocolate chip cookies

Homo and Hetero Video Clip

Miscibility- some liquids can dissolve in others like gasoline- they are miscible

Liquids that don’t dissolve are immiscible oil and water

Gases can dissolve in liquids example –soda and meringue

The meringue in this pie is amixture of air and liquid eggwhite that has been beatenand then heated to form asolid foam.