Exam 1 Review:  Chapter 2 - Other Chemistry Terms

chemical reaction - The process in which one or more substances (elements, ions, or molecules), the "reactants," are changed into others, the "products;" there is no change in mass nor in the number of atoms of specific elements, but the arrangements of the atoms, controlled by chemical bonds, are changed; there are also always changes in the energy states of some or all of the participants and some chemical energy is lost to the environment as waste heat, i.e., the energy transformations are not 100% efficient.

examples:

dehydration synthesis - Any anabolic chemical reaction in which two of the atoms in the smaller reactant molecules ("building blocks," subunits, monomers) form new covalent bonds by the donation of a hydrogen atom (-H) from one reactant and a hydroxyl group (-OH) from another reactant to form a water molecule (H-O-H = H₂O) while the remainders of the two reactants form a single covalent bond where the -H and -OH were removed, thus producing a larger molecule or polymer; such reactions are endergonic, i.e., they require a considerable input of chemical energy.  [Note:  It is the reverse of a hydrolysis reaction.]

decomposition reaction - Any catabolic chemical reaction in which the reactant, a larger molecule, is separated into two or more smaller molecules or atoms, the products, which had been joined to each other by chemical bonds; such reactions are exergonic, i.e., they yield an output of chemical energy.   [Note:  It is the reverse of a synthesis reaction.]

synthesis reaction - Any anabolic chemical reaction in which the reactants, two or more smaller atoms or molecules, the reactants, are combined into a larger molecule, the product, the reactants have been joined to each other by chemical bonds; such reactions are endergonic, i.e., they require a significant input of chemical energy.   [Note:  It is the reverse of a decomposition reaction.]

hydrolysis - Any catabolic chemical reaction in which the single covalent bond between two of the atoms in a larger molecule or polymer is broken, while at the same time a water molecule (H-O-H = H₂O) is broken into its constituent hydrogen atom (-H) and hydroxyl group (-OH), and two new bonds are formed: (1) in which the hydroxyl group (-OH) is added, forming a new single covalent bond, to one of the smaller breakdown products (subunits, monomers)  while (2) the hydrogen atom (-H) is added, forming the second single covalent bond, to the other of the smaller breakdown products (subunits, monomers); such reactions are exergonic, i.e., they yield a modest output of chemical energy, primarily in the form of waste heat.  [Note:  It is the reverse of a dehydration reaction.]

oxidation - Any chemical reaction in which the atoms in an element lose electrons and the valence of the element is correspondingly increased; the products of such reactions tend to have less potential chemical energy; often, but not always, the loss of electrons is caused by the addition of an oxygen atom to the molecule; they always occur coupled to reduction reactions.

reduction - Any chemical reaction in which one or more hydrogens is combined with a compound or in which one or more oxygens is removed from a compound; is  such reactions, there is a decrease in the positive valence or an increase in negative valence by the gaining of electrons; the products of such reactions tend to have more potential chemical energy; they always occur coupled to oxidation reactions.

activation energy - The minimum input of energy which a system must acquire from some outside source before a chemical reaction will occur.

exergonic - The adjective used to describe those (usually catabolic) chemical reactions in which the potential chemical energy ("free energy") of the products is less than the potential chemical energy ("free energy") of the reactants and the rest of the energy has been released from the reaction as some form of kinetic energy, always including the release of some waste heat.

Reactant(s) ↔ Products(s) + energy + waste heat

endergonic  - The adjective used to describe those (anabolic) chemical reactions in which the potential chemical energy ("free energy") of the products is greater than the potential chemical energy ("free energy") of the reactants and, therefore, energy has to be provided to the reaction as some form of kinetic energy input in order for the reaction to occur.  [Note:  because all chemical reactions are less than 100% efficient, the reaction will also include the release of some waste heat.]

Reactant(s) + energy ↔ Products(s) + waste heat

acid - A substance which dissolves in water to release H⁺ ions, and some corresponding negative ion(s); a proton donor in chemical reactions.

acidic solution - A mixture, a solution, of water and various chemicals, some of which are able to release  hydrogen ions (H⁺⁾ into the mixture/solution, such that the pH of the solution is less than 7; such solutions have a great concentration of hydrogen ions (H⁺) than hydroxyl ions (OH^-).

base - A substance which dissolves in water to release OH^- ions, and some corresponding positive ion(s); a proton acceptor in chemical reactions.

basic = alkaline solution - A mixture, a solution, of water and various chemicals, some of which are able to release hydroxyl ions (OH^-) into the mixture/solution, such that the pH of the solution is greater than 7; such solutions have a great concentration of hydroxyl ions (OH^-) than hydrogen ions (H⁺).

pH - pH is a mathematical expression indicating how acidic or alkaline a water-based solution is. The pH scale extends from 0 (most acid) to 14 (most basic = alkaline). The pH of a solution is the negative log of the hydrogen ion concentration.

buffer - - A chemical or mixture of chemicals, usually a weak acid or base and its corresponding salt, which minimizes change in the acidity of a solution, the pH, when an acid or base is added to the solution.

salt - The product of any reaction in which an acid and a base combine to yield water and various ions or electrolytes; these compounds usually crystallize when dry.

solution - Any homogeneous mixture of two or more substances in which the various solutes are dissolved in the solvent in such a way that each individual atom or molecule of the solute is independently dissolved in the solvent substance; such a mixture may be in any physical phase, solid, liquid, or gas.

solvent - Any substance in which other substance may be dissolved, forming a solution, a colloid, or a suspension; generally, the proportion of the solvent exceeds the proportion(s) of the solute(s); two broad classes are recognized, those, such as water, which have polar covalent bonds and readily dissolve other substances which are charged or partially charged, and those, such as oils, which have nonpolar covalent bonds and readily dissolve other uncharged substances; such a substance may be in any physical phase, solid, liquid, or gas, but typically they are liquids.

solute - Any substance dissolved in another substance, usually the component(s) of a solution present in the lesser amount(s); the dissolved substance(s) in a solution; the component of a solution may change its state, e.g., the gas, oxygen or the solid, sodium chloride, enter the liquid state formed by the solvent when dissolved in water.  [Note:  the degree to which a solvent dissolves a given solute is termed the solubility of that solute in that solvent.]

polar solvent - Any compound, e.g., water (H₂O) or liquid ammonia (NH₃), which contains some (or all) polar covalent bonds, such that the molecule contains two or more regions which carry partial electrical charges, and, as a result, is capable of dissolving other charged or partially charged ("polar") materials such as other molecules with polar covalent bonds or charged ions.  [Note:  polar solvents are attracted to their solute particles by hydrogen bonds.]

For some interesting animations about the chemistry of water, visit John Kyrk's web site.

nonpolar solvent - Any compound, e.g., gasoline or benzene, which contains primarily non-polar covalent bonds, such that the molecule is neutral or uncharged (contains no regions which carry partial electrical charges), and, as a result, is capable of dissolving other uncharged ("nonpolar") materials such as other molecules with nonpolar covalent bonds, e.g., lipids.  [Note:  nonpolar solvents are attracted to their solute particles by hydrophobic bonds = van der Wals attractions.]

suspension -  A system (a mixture of chemicals) in which microscopically visible bouyant particles are dispersed (as opposed to dissolved as individual molecules) throughout a less dense liquid or gas from which they are easily filtered but not easily settled out of solution by gravity because of system viscocity or molecular interactions.  [Note:  examples include milk and blood plasma.]

colloid = colloidal suspension - -  A system (a mixture of chemicals) in which microscopically/macroscopically visible particles (which are approximately 10 to 10,000 angstroms in size) are dispersed (as opposed to dissolved as individual molecules) throughout a less dense liquid or gas; such particles may be filtered (with the appropriate small pore size filter) and can be settled out of solution by gravity if left undisturbed for a sufficient period of time.  [Note:  examples include whole blood and smoke.]

heat capacity - The amount of heat required to raise the temperature of one mole or one gram of a substance by one degree Celsius without a change of phase.  aka - thermal capacity and specific heat

List:

 3. the components of an acid, a base, and a salt.

 

Acid	Base	Salt
One or more negative ions (anions) other than the hydroxyl ion (OH-) and one or more hydrogen ions (H+)	One or more positive ions (cations) other than the hydrogen ion (H+) and one or more hydroxyl ions (OH-)	One or more negative ions (anions) other than the hydroxyl ion (OH-) and one or more positive ions (cations) other than the hydrogen ion (H+); usually formed from the combination of an acid and a base

Describe:

1. the relationship between H⁺ and OH^- in a solution at pH 6.

Any solution with a pH less than 7 has more H⁺ ions and fewer OH^- ions.  Because the pH scale is logarithmic, a solution with a pH = 6 has 10 times more H⁺ ions than a neutral solution (pH = 7) and 10 times fewer OH^- ions than a neutral solution (pH = 7).