Key Concepts in Chemistry and Chemical Reactions

pH Scale

Used to measure how acidic or basic a substance is and ranges from 0-14

Neutral Substance

pH 7, neither acidic nor alkaline

Acid

pH lower than 7

Base

pH higher than 7

Electrostatic

Stationary electrical charges that are different from electrical currents

Molarity

A measure of the concentration of solute per liter of solvent. M=mol/L

Reversible Reaction

A reaction in which the conversion of reactants to products and products to reactants occurs simultaneously.

Equilibrium

A condition in the course of a reversible reaction in which there is no net change in the amount of products and reactants

Acids

Substances that increase the concentration of H+/H₃O+ ions in solutions. Always start with an H atom because they donate H to their solutions

Bases

Substances that increase the amount of OH- (hydroxide) ions in solutions. Substances that accept H+ ions in solutions.

Bromthymol Blue

Method to test pH of a substance. Turns yellow when pH is below 6 and blue when pH is above 7.6

pH Strips

Method to test pH of a substance. Changes color based of pH of a substance, uses a key.

Dimensional analysis

A mathematical process that is used to convert between units using conversion factors

Conversion factors

A mathematical relationship between one unit of measurement and another

Limiting reactants

The reactant used up in a chemical reaction, which limits the amount of product that can form

Ratio

The quantitative relation between two amounts showing the number of times one value contains or is contained within the other.

Percent yield

The percent ratio of actual yield to the theoretical yield [(actual yield/theoretical yield)x100]

Theoretical yield

The amount of product we predict if everything is 100% used

Actual yield

The amount of product that is actually being produced

Stoichiometry

The quantitative relationship between a reactant and a product in a chemical reaction

Mole Ratios

In a balanced equation, the coefficients tell the ratio in moles between any two compounds involved in a chemical reaction

Mole

A unit of measurement

Grams

A metric unit of mass

Liters

A metric unit of capacity/volume

Particles

Atoms, molecules, formula units

Molar Mass

The mass in grams of 1 mole of a substance

Avogadro's Number

6.022x10²³

M

The unit used to represent molar mass

n

The unit used to represent the number of moles of a substance.

Coefficient

How many "copies" are present

Subscript

How many atoms of that element are in one molecule

Arrows/yields

Indicates in which direction the reaction occurs

Law of Conservation of Mass

No matter in the universe can be created or destroyed in chemical reactions

Molecule

A neutral group of 2 or more bonds

Chemical Bond

A force that holds atoms together in a molecule or compound.

Octet Rule

Atoms tendency toward having 8 electrons in their valence shell

Ionic Bond

A bond formed when atoms transfer from one atom to another

Oxidation Number

A number that indicates how many electrons have been lost or gained by that ion.

Covalent Bonds

A bond that forms when two atoms share electrons to achieve a full outer shell.

Electron Energy Levels

The specific energies that an electron can have

Orbitals

Regions within sublevels where electrons are likely to be found

Isotopes

A different form of an element that has a different mass than the one on the periodic table

Electronegativity

A measure of how 'hungry' an atom is for electrons

Valence Electrons

The outermost electrons

Pauling Scale

Measures electronegativity from 0-4.0

Lewis Dot Structure

The model that shows valence electrons around the symbol

Ion

An atom with gained or lost electron(s)

Anion

A negative ion

Cation

A positive ion

Atomic Size

The size of an element

Protons

Positively charged particles with a mass of 1 AMU

AMU

The unit used to measure atomic mass (Atomic Mass Unit)

Neutrons

Neutrally charged (no charge) particles with a mass of 1 AMU

Electrons

Negatively charged particles with a mass so small its negligible (thought of as 0AMU)

Atomic Number

The number of protons in the nucleus as well as the number of electrons in the electron cloud of a neutral isotope

Mass Number

The mass of the element

Evaporation

The process that changes a liquid to gas, removing the liquid of a substance

Magnetic Separation

Using a magnet to remove the magnetic substance of a mixture

Physical Separation

Physically picking apart a mixture

Filtration

Sifting or using filter paper to separate things

Sedimentation

The use of gravity or other chemical means to cause a substance to sink to the bottom

Distillation

Separation through boiling, capturing vapor, and recondensing a liquid without 'impurities'

Chromatography

The separation of compounds through capillary action

Capillary Action

The movement of a liquid through or along another material.

Heat

The speed of movement of particles

Sublimation

A solid becoming a gas with no liquid stage. Occurs when below triple point.

Triple Point

A very specific temperature and pressure where a substance moves freely between solid, gas, and liquid forms. Different for all substances.

Specific Heat

The amount of heat required to change the temperature of exactly 1g of a substance by 1ºC, represented in joules.

Chemical Property

A characteristic or behavior of a substance that can be observed or measured when that substance undergoes a chemical reaction.

Chemical Changes

A change in a substance that has undergone a chemical reaction

Mixtures

A combination of 2 or more pure substances in which each retains its individual properties

Solutions

Air, contact solution, detergent, slime, alloys

Solvent

Liquid; does the dissolving of the solute

Solute

What is dissolved in the liquid

Heat Capacity

The number of heat units needed to raise the temperature of a body by one degree.