Chemistry Unit 5 Key Terms

Physical Properties

the characteristics of a substance that can be observed or measured without chemically changing the substance. Can be intensive or extensive.

Physical Change

A change in a substance that does not involve a change in the identity of the substance. No new substance is made. Includes making mixtures (dissolving in water) and phase changes.

Chemical Properties

Characteristics of a substance that determine how it will chemically react. I.e. flammability

Chemical change/ chemical reaction

A change in which the composition of the substance changes, thus a new substance is made. I.e. burning, cooking, ripening, rusting, forming a compound from elements

Phase change / state change

A change from one state of matter to another without a change in chemical composition.

Melting

The change in state from a solid to a liquid, absorbs energy, forces of attraction are weakened

Boiling/vaporization

Change in state from Liquid to gas (at boiling point), absorbs energy, forces of attraction are broken

Sublimation

A change directly from the solid to the gaseous state without becoming liquid, absorbs energy

Freezing

The change of state from a liquid to a solid, releases energy

Condensation

The change of state from a gas to a liquid, energy is released

Deposition

State change from gas to solid, releases energy

Intramolecular forces

Chemical bonds (especially covalent bonds within a molecule)

Intermolecular forces (IMFs)

Forces of attraction between molecules, weaker than actual bonds

Ionic bond/ion-ion attraction

The strong attraction between cations and anions in an ionic compound

Lattice

Large group of ions organized in a certain pattern

Covalent bond

A chemical bond that involves sharing electrons between nonmetal atoms in a molecule

Nonpolar molecule

A molecule that does not have an overall dipole moment. Passes both "tests"

Polar molecule

A molecule that has an overall dipole moment, fails at least one of the "tests"

Dipole-dipole attraction

The type of IMF between polar molecules

Hydrogen-bonds

The type of IMF between extremely polar molecules (containing "special" hydrogens). NOT ACTUALLY A BOND, just the strongest type of IMF

London dispersion forces (LDFs)

The weakest type of IMF, result from temporary attractions in nonpolar molecules

Melting Point

The temperature at which a substance melts if absorbing energy or freezes if losing energy

Boiling point

The temperature at which a substance vaporizes (boils) if absorbing energy or freezes if losing energy

Heat of fusion

The amount of energy (or time) required to melt a substance

Heat of vaporization

The amount of energy (or time) required to boil a substance

Specific heat capacity

The amount of energy (or time) required to increase the temperature of a substance

Kinetic energy

Energy related to motion (how fast the particles are moving) - measured by temperature

Potential energy

Energy that results from the position of objects relative to each other (the type of energy that's changing during a phase change)

Homogeneous Mixture - Solution

A mixture in which the composition is uniform throughout. Can still be physically separated.

Solute

The substance that there is less of in a solution (usually what's being dissolved)

Solvent

The substance that there is more of in a solution (usually water)

Solubility

Whether or not the substance CAN dissolve, or more specifically how MUCH can dissolve in a certain amount of water

Soluble

Able to dissolve in water. Will form attractions to water molecules. Includes polar molecules and most ionic compounds.

Insoluble

Unable to dissolve in water. Will not form attractions to water molecules. Includes nonpolar molecules and some ionic compounds.

Concentration

A measure of how much solute is currently dissolved in a certain amount of water.

Dilute

The solution contains only a small amount of solute (has a low concentration)

Concentrated

The solution contains a large amount of solute (has a high concentration)

Colloid

A type of heterogeneous mixture (may look homogeneous to the naked eye) in which particles exist in separate states of matter. Includes foam, gels, emulsions, suspensions, aerosols, etc.

Filtration

A method of separating a mixture that uses a difference in state of matter or particle size. I.e. trapping a solid while letting liquid pass through.

Distillation

A process that separates the substances in a solution based on their boiling points

Chromatography

A technique that is used to separate the components of a mixture based on differences in polarity and/or color

Aqueous (aq)

meaning dissolved in water, can be used as a state symbol

Dissociation

the separation of ions that occurs when an ionic compound dissolves in water

Electrolyte

A substance that is soluble AND dissociates into ions when dissolved in water, resulting in a solution that is highly conductive of electricity

Nonelectrolyte

A substance that is either insoluble or does not dissociate when dissolved in water

Unsaturated

The solution contains less than the maximum possible amount of solute

Saturated

The solution contains the maximum possible amount of solute (and may have excess solid that is undissolved)

Recrystallization

When a substance comes back out of a solution as a solid (is no longer dissolved in the water)