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.