Wk 1-2 - Atoms, Molecules, Water, Solutions

Matter

It makes up the physical world.

Element

A pure substance of matter that has distinct physical and chemical properties.

Atom

Smallest unit of an element that retains the element's distinctive properties.

Nucleus

Dense core of atoms.

Protons

Positively charged particles.

Neutrons

Neutrally charged particles.

Electrons

Negatively charged particles orbiting the nucleus.

Ion

An atom that has an electrical charge (+ or -).

Atomic Number

The number of protons in an atom.

Atomic Mass Number

The total number of protons and neutrons contained in the nucleus.

Isotope

Atoms of an element that have the same number of protons, but different numbers of neutrons.

Atomic Mass Unit

A measurement of mass of subatomic particles.

Molecule

Atoms linked together.

Chemical Reaction

Process of linking atoms or molecules together or tearing them apart.

Chemical Bond

Attractive forces that hold atoms together.

Ionic Bond

A bond where atoms are held together by opposite electrical charges.

Covalent Bond

A strong bond where two atoms share electrons.

Nonpolar

No charge on any part of the molecule.

Polar

A bond where one atom exerts a stronger attraction on the electrons than does the other, forming slight partial charges.

Hydrogen Bond

An electrical attraction that occurs between two polar molecules.

Cohesion

The tendency of water molecules to stick together.

Surface Tension

Tendency of a water surface not to break.

Adhesion

The tendency of water molecules to cling to other substances.

Capillary Action

The movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension.

Solvent

A substance that completely surrounds and disperses (dissolves) the atoms or molecules of another substance.

Solute

Any substance that can be dissolved by a solvent.

Solution

A fluid where a solute is dissolved in a solvent.

Hydrophilic

Molecules (ions and polar molecules) that are attracted to and dissolved in water.

Hydrophobic

Larger non-polar molecules (fats, oils) that do not dissolve in water.

Specific Heat

Amount of energy needed to raise one gram of water 1 degree Celsius.

Heat of Vaporization

Amount of energy needed to cause a substance to evaporate.

Neutral pH

Pure water has equal concentrations of H+ and OH- ions (pH = 7).

Acid

The concentration of H+ ions exceeds that of the OH- ions (pH < 7).

Base

The concentration of OH- ions exceeds that of the H+ ions (pH > 7).

Buffer

A molecule that tends to maintain a solution at nearly constant pH.