Topic #1 Basics of Chemistry & Matter

Elements

Fundamental building blocks of matter

Matter

• Has mass & takes up space

• Can be understood in terms of arrangements & rearrangements of atoms

Atoms retain their identity in chemical reactions

Except when a substance is radioactive (unstable nucleus)

Elements

Can be diatomic or monoatomic

Compounds

Can be binary or ternary

Substance

• A form of matter that has a definite composition and distinct properties

• Composed of atoms

• Compounds form in definite proportion

ex. water

Chemistry

The study of changes in matter and the energy needed to make these changes.

States of Matter

Changes of state involving altering IMFs not altering actual chemical bonds.

Liquid —> Gas

Boiling, vaporizing, evaporating

Gas —> Liquid

Condensing, liquefying

Entropy

A measure of disorder or randomness in a system, or how spread out energy is.

• Solid have the least entropy: Particles are in a tightly packed, highly ordered, fixed arrangement.

• Gas has the most entropy: Particles are far apart, highly disordered, and have the most freedom to move.

Mixtures

• No energy changes

• Variable composition

• Components retain their characteristic properties

• Mixtures of different compositions may have widely different properties

• Can be physically separated

Mixture → Pure substance

May be separated into pure substances by physical methods.

Pure substances

• Fixed composition

• Cannot be separated into simpler substances by physical methods

• Can only be changed in identity and properties by chemical methods

• Properties do not vary

Mixtures can be?

Can be evenly distributed or not uniform

Homogeneous mixture (evenly distributed)

• Have same composition throughout

• Components are visibly indistinguishable

• Solutions ~ gaseous & aqueous! Solute in solvent

Heterogeneous mixture

• Do not have the same composition throughout

• Components are visibly distinguishable

• Filter insoluble residue

Pure substance can be?

Decomposed or can’t be decomposed

Pure substances that can be decomposed are compounds

Can be decomposed into simpler substances by chemical changes. Always in a definite ratio.

Pure substances that can’t be decomposed are elements

Cannot be decomposed into simpler substances by chemical changes.

Diatomic Elements

Br, I, N, Cl, H, O, F

Allotropes

Different forms of the same element. Different structure & properties.

ex. diamond and graphite

Evaporation (A method to physically separate a mixture)

• Separating a mixture (solution) of a soluble solute and a solvent (salt in water).

• Heating the solution until the solvent evaporates leaving behind the solid residue.

Fractional Distillation (A method to physically separate a mixture)

Used to separate a solution of 2 or more miscible (soluble) liquids by varying boiling points.

Chromatography

• Based on solubility.

• The solvent and paper both have an attraction for the components in a mixture. If a material is placed on one spot on the paper and is soluble in the liquid solvent, the material will be dissolved when the solvent moves over it.

• When we get to solutions ~ Like dissolves like.

Compounds

A pure substance composed of atoms of two or more elements chemically combined in fixed proportion.

Binary compound

2 types of elements

Ternary compound

3 types of elements. May have a polyatomic ion.

Compounds can only be separated into their pure compounds (elements) by…

Chemical changes.

Ionic compound

• Form one crystalline lattice structure

• Metal (cation) + Nonmetal (anion)

• Transfer of electrons

Molecular compounds

• Soft substances, poor conductors

• Molecules held together by covalent bonds and intermolecular forces.

• London Dispersion (VDW) ~ nonpolar

• Dipole-Dipole ~ polar

• H-Bonds ~ H with F, O, N

Extensive Property

Depends upon how much matter is being considered.

ex. mass, length, volume

Intensive Property

Does not depend on how much matter is being considered.

ex. density, temperature, color

Intermolecular forces

An attraction between two molecules.

Intramolecular force

A bond within a molecule that holds the atoms together.

London Dispersion Forces

• The weakest attractive forces between molecules or atoms are caused by shifts in the distribution of electrons, which creates temporary uneven charges (temporary dipoles).

• Stronger in larger atoms and molecules

• Present in all substances

Dipole-Dipole Forces

Attraction between molecules with permanent partial charges (polar molecules).

Hydrogen Bonding

A stronger type of dipole-dipole force which occurs in molecules with bonds of H with F, O, and N.

Ion-Dipole

Attractions that occur between a charged ion and a polar molecule.

Mole

A unit used by chemists to express the amount of a compound or element.

Avogadro’s number

6.02 x10^(23), the number of particles (molecules, ions, atoms) in a mole of any substance.

Molecular implies what?

Covalent bonding

Empirical Formula

The most reduced form of a chemical formula. The ratio necessary for all ionic substances.

The Law of Constant Composition

States that any sample of a pure compound always consists of the same elements combined in the same proportions by mass.

Synthesis

Atoms of elements combine to form a compound.

ex. 4Fe + 3O₂ —> 2Fe₂O₃

Decomposition

Compound is broken down into its component elements or simpler compounds.

ex. 2H₂O —> 2H₂ + O₂

Single Replacement

A single element reacts with a compound to take the place of an element of similar character. This results in the formation of a new compound and a new free element.

ex. Cu + 2 AgNO₃ —> Cu(NO₃)₂ + Ag

Double Replacement

Two compounds react to produce two new compounds (elements switch places).

ex. AgCl + KNO₃ —> AgNO₃ + KCl

Combustion

CH and/or O + O₂ —> CO₂ (g) + H₂O (g)

The Law of Conservation of Matter

Matter can be neither created nor destroyed.

Coulombs Law

Quantifies the amount of force between two objects.

• Magnitude of the electrostatic force of attraction or repulsion between two points is directly proportional to the product of the magnitude of the charges.

• Attraction is inversely proportional to the distance between them.

Stoichiometry

The study of quantities of materials consumed and produced in balanced chemical reactions.

• Math done to change a substance to another substance

All carbonates break down to?

The metal oxide and carbon dioxide gas.

Na₂CO₃ —> Na₂O + CO₂

All chlorates break down to?

The metal chloride and oxygen gas.

Ba(ClO₃)₂ —> BaCl₂ + 3 O₂

Metal hydroxides break down to?

Metal Oxide + Water

Cu(OH)₂ —> CuO + H₂O

Oxy acids break down to?

Non-metal oxide (with the nonmetal having the same valence) + Water

2H₃PO₄ —> P₂O₅ + 3 H₂O

Any time H₂CO₃ is formed it results in…

—> CO₂ + H₂O

Metal oxide + Carbon dioxide forms what?
ex. K₂O + CO₂ —> ?

Metal carbonate

K₂O + CO₂ —> K₂CO₃

Metal chloride + Oxygen forms what?

ex. BeCl₂ + 3 O₂ —> ?

Metal chlorate

BeCl₂ + 3 O₂ —> Be(ClO₃)₂