Matter

any substance that possesses weight and takes up space;

Solids

matter with three dimensions and a definite shape and volume and the most compact state;

Liquids

matter that flows freely and is less compact than solids and fills containers;

Gases or Vapors

the least compact state with no definite shape or volume and expands indefinitely;

Mass

the amount of matter in an object and always constant and measured with a balance;

Weight

the heaviness of an object and equals mass times gravitational pull and changes with gravity;

Element

the simplest form of matter that cannot be broken down by normal chemical or mechanical means;

Atom

the structural unit of an element;

Proton

a positively charged particle located in the nucleus;

Neutron

a particle with no charge located in the nucleus;

Electron

a negatively charged particle located in shells outside the nucleus;

Atomic number

the number of protons and also the number of electrons;

Atomic mass

the sum of protons and neutrons;

Isotope

atoms of the same element with different neutron numbers and different atomic mass;

First shell

holds up to two electrons;

Second shell

holds up to eight electrons;

Third shell

holds up to eight electrons;

Fourth shell

holds up to eight electrons;

Valence shell

the outermost shell that holds valence electrons and determines stability;

Ion

an atom with a charge formed by gaining or losing electrons;

Cation

a positively charged atom formed by losing electrons;

Anion

a negatively charged atom formed by gaining electrons;

Molecule

a group of atoms bonded together;

Compound

a molecule made of different atoms bonded together;

Organic compound

a compound that contains carbon oxygen and hydrogen;

Inorganic compound

a compound that lacks carbon or has carbon without hydrogen or oxygen;

Chemical formula

a shorthand notation showing the number of each atom type;

Structural formula

a diagram showing the arrangement of atoms;

Isomers

molecules with the same chemical formula but different structural formulas;

Ionic bond

a bond formed by the transfer of electrons between atoms and is weak;

Covalent bond

a bond formed by sharing electrons and is strong;

Single covalent bond

one pair of electrons shared;

Double covalent bond

two pairs of electrons shared;

Polar covalent bond

a covalent bond with unequal sharing of electrons creating positive and negative ends;

Hydrogen bond

a weak attraction between a positively charged hydrogen and a negatively charged oxygen nitrogen or fluorine on another molecule;

Water

the most important inorganic compound making up fifty to ninety percent of organisms and sixty percent of humans;

Temperature stability

the property of water requiring enormous energy to change temperature;

Polarity of water

water has a positive hydrogen end and a negative oxygen end;

Cohesion

the attraction of water molecules to each other due to hydrogen bonds;

Surface tension

the tight bonding of water molecules at the surface due to cohesion;

Adhesion

the attraction of water molecules to other substances;

Solvent

a fluid or gas that dissolves particles;

Solute

particles dissolved in a solvent;

Universal solvent

water dissolves most substances and dissolves only polar solutes;

Density of water

liquid water has a density of one gram per milliliter and ice has a density less than one so ice floats;

pH

a measure of hydrogen ion concentration;

Neutral pH

pH seven where hydrogen ions equal hydroxyl ions;

Acid

a substance with pH less than seven and more hydrogen ions than hydroxyl ions;

Base

a substance with pH greater than seven and fewer hydrogen ions than hydroxyl ions;

Buffer

a molecule that prevents large changes in pH and helps maintain homeostasis;