Chapter 2 Flashcards
Matter
Matter is anything that takes up space and has mass. Organisms are composed of matter.
Element
A substance that cannot be broken down to other substances by chemical reactions. Matter is made up of elements.
Compound
A substance consisting of two or more elements in a fixed ratio.
Essential Elements
Those needed by an organism to live a healthy life and reproduce.
Trace Elements
Required only in minute quantities.
Atom
The smallest unit of matter that still retains the properties of an element.
Subatomic Particles
Smaller particles that compose atoms.
Atomic Nucleus
The center mass of an atom. Composed of protons and neutrons.
3 Subatomic Particles
Neutrons, Protons, Electrons
Mass Number
The sum of protons and neutrons in the nucleus of an element.
Atomic mass
The total mass of an atom, can be approximated by the mass number.
Isotope
Different atomic forms of an element that differ in the number of neutrons. Radioactive isotopes decay spontaneously, giving off particles and energy.
Energy
The capacity to cause change.
Potential energy
The energy matter has because of its location or structure.
Electron shells
Characteristic average distances from the nucleus inhabited by electrons.
Properties of the electron shell
Energy level increases with distance from the nucleus. Electrons can move to higher or lower shells by absorbing or releasing energy respectively.
Valence Shell
Outermost shell of an atom. Chemical behavior of an atom mostly depends on the number of electrons in the valence shell.
Valence Electrons
Electrons that occupy the valence shell.
Chemical Bonds
Attractions between atoms with incomplete valence shells caused by the sharing of valence electrons.
Covalent Bond
The sharing of a pair of valence electrons by two atoms. The shared electrons count as a part of each atom’s valence shell.
Molecule
Two or more atoms held together by covalent bonds.
Single Bond/Double Bond
The sharing of one or two pairs of electrons.
Valence
The bonding capacity of an atom, the number of bonds that the atom can form. Usually corresponds to the number of electrons required to complete the atom.
Pure Elements
Composed of molecules of one type of atom. Such as H2 and O2.
Compounds
Molecules composed of two or more types of atoms.
Electronegativity
An atom’s attraction for the electrons of a covalent bond. The more electronegative an atom, the more strongly it pulls shared electrons toward itself.
Nonpolar Covalent Bond
Atoms share the electrons equally.
Polar Covalent Bond
One atom is more electronegative and the atoms do not share the electrons equally. Causes a partial positive or negative charge for each atom or molecule.
Ions
Two oppositely charged atoms (or molecules) resulting from one atom stripping electrons from its less electronegative bonding partner.
Cation
Positively charged ion.
Anion
Negatively charged ion.
Ionic Bond
An attraction between an anion and a cation.
Ionic Compounds/Salts
Compounds formed by ionic bonds.
Weak Chemical Bonds
Ionic bonds, Hydrogen bonds, Van Der Waals interactions
Hydrogen Bond
Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom nearby.
Van der Waals Interactions
When electrons are distributed asymmetrically in molecules or atoms resulting in regions of negative or positive charge enabling all atoms and molecules to stick to one another.
Chemical Reactions
The making and breaking of chemical bonds.
Reactants
The starting molecules of a chemical reaction.
Products
The final molecules of a chemical reaction.
Chemical Equilibrium
When the forward and reverse reaction rates are equal.
Emergent Properties of water which contribute to earth’s suitability for life
Cohesive behavior, Ability to moderate temperature, Expansion upon freezing, Versatility as a solvent
Polar Molecule
Molecule whose charge is unevenly distributed (water).
Cohesion
When molecules stay close together.
Adhesion
The clinging of one substance to another.
Surface tension
A measure of how hard it is to break the surface of a liquid.
Kinetic energy
The energy of motion.
Thermal energy
A measure of the total kinetic energy due to molecular motion.
Temperature
The average kinetic energy of molecules.
Heat
Thermal energy in transfer from one body of matter to another.
Calorie
The amount of energy needed to raise the temperature of 1g of water by 1 degree celsius.
Kilocalories (kcal)
1 kcal = 1000 cal.
Joule (J)
1 J = 0.239 cal or 1 cal = 4.184 J.
Specific Heat
The amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1 degree Celsius.
Heat of evaporation
The heat a liquid must absorb for 1 g to be converted to a gas.
Evaporative cooling
The process by which as liquid evaporates, its remaining surface remains cool.
Solution
A liquid that is a homogeneous mixture of other substances.
Solvent
A dissolving agent of a solution.
Solute
The substance that is dissolved.
Aqueous Solution
One in which water is the solvent.
Hydration Shell
A sphere of water molecules that surround each ion when an ionic compound is dissolved in water.
Hydrophilic/Hydrophobic substances
Substances which have an affinity for water or do not respectively.
Molecular Mass
The sum of all masses of all atoms in a molecule.
Hydroxide ion
Left behind when a hydrogen ion is transferred from one water molecule to another.
Hydronium ion
The water molecule which receives the extra proton.
Acids
Increase the concentration of hydronium ions in water. pH < 7
Bases
Reduces the concentration of hydronium ions in water. pH > 7
pH
The negative logarithm of hydronium ion concentration.
Buffers
Substances that minimize changes in concentrations of H+ and OH- in a solution.
Ocean Acidification
When CO2 dissolved in seawater forms carbonic acid.
