2: Chemistry Comes Alive

Matter

It is anything that occupies space and has mass.

Solid

Has a definite shape and volume.

Liquid

Has a definite volume, but they conform to the shape of its container.

Gas

Has neither a definite shape nor a definite volume.

Energy

The capacity to do work, or to put matter into motion.

Kinetic energy

Energy in motion/action.

Potential energy

Stored energy, an inactive energy that has the capability to do work, but is not presently doing so.

Chemical energy

It is the form stored in the bonds of chemical substances.

Electrical energy

Energy that results from the movement of charged particles.

Mechanical energy

Energy directly involved in moving matter.

Radiant energy

Also called electromagnetic energy — Energy that travels in waves.

Elements

Unique substances that cannot be broken down into simpler substances by ordinary chemical methods.

Periodic Table

A table that provides a more complete listing of the known elements and helps to explain the properties of each element that make it react as it does with other elements.

Atoms

Building blocks or, more or less identical particles of which an element is composed of.

Physical properties of atoms

Those we can detect with our senses or measure.

Chemical properties of atoms

Pertain to the way atoms interact with other atoms (bonding behavior) and account for the facts that iron rusts, animals can digest their food, and so on.

central nucleus

An atom has a \____ containing protons and neutrons tightly bound together.

Proton

A subatomic particle that bears a positive electrical charge.

Neutron

A subatomic particle that is neutral.

Electrons

A subatomic particle that bears a negative charge equal in strength to the positive charge of the proton.

Planetary Model

A simplified model of atomic structure.

Orbitals

Regions around the nucleus in which a given electron or electron pair is likely to be found most of the time.

Orbital Model

A more modern model of atomic structure, which is more useful for predicting the chemical behavior of atoms.

atomic number

The \_______ of any atom is equal to the number of protons in its nucleus and is written as a subscript to the left of its atomic symbol.

mass number

sum of the masses of its protons and neutrons.

Isotopes

A structural variation that all known elements have — it has the same number of protons, but differ in the number of neutrons they contain.

Atomic weight

An average of the relative weights (mass numbers) of all the isotopes of an element, taking into account their relative abundance in nature.

Radioactivity

The process of atomic decay.

Radioisotopes

Isotopes that exhibit the behaviour of radioactivity.

Half-Life

The time required for a radioisotope to lose one-half of its activity.

Molecule

A combination of two or more atoms held together by chemical bonds.

Mixtures

These are substances composed of two or more components physically intermixed.

Solutions

These are homogeneous mixtures of components that may be gases, liquids, or solids.

Solvent

Substance present in greatest amounts.

Solute

Substance present in smaller amounts.

Water

The body’s chief solvent. An unparalleled solvent.

true solutions

Most solutions in the body are \_____ containing gases, liquids, or solids dissolved in water. These solutions are usually transparent.

percent

Solutions used in a college laboratory or a hospital are often described in terms of the \_______ of the solute in the total solution.

Avogadro’s number

One mole of any substance always contains exactly the same number of solute particles, that is, 6.02 x 10^23.

Colloid

Also called emulsion, — are heterogeneous mixtures, which means that their composition is dissimilar in different areas of the mixture.

Sol-gel transformation

A unique property of colloid that change reversibly from a fluid (sol) state to a more solid (gel) state.

Cytosol

The semifluid material in living cells, is also a colloid, largely because of its dispersed proteins.

Suspensions

These are heterogeneous mixtures with large, often visible solutes that tend to settle out.

electron shells

Electrons forming the electron cloud around the nucleus of an atom occupy regions of space called \_____ that consecutively surround the atomic nucleus.

Valence Shell

It indicates an atom’s outermost energy level or that portion of it containing the electrons that are chemically reactive.

octet rule

The key to chemical reactivity

Ionic Bond

A chemical bond between atoms formed by the transfer of one or more electrons from one atom to the other.

Ions

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Electron acceptor

The atom that gains one or more electrons.

Anion

A net negative charge.

Electron donor

The atom that loses electrons.

Cation

A net positive charge.

Crystals

Large arrays of cations and anions held together by ionic bonds.

Covalent Bond

Electron sharing produces molecules in which the shared electrons occupy a single orbital common to both atoms.

Nonpolar molecules

The molecules formed are electrically balanced. There has no separation of charge, so no positive or negative poles are formed.

Polar molecule

A molecule containing polar bonds where the sum of all the bond's dipole moments is not zero.

Electronegativity

The tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond.

Electropositivity

A measure of an element's ability to donate electrons, and therefore form positive ions; thus, it is antipode to electronegativity.

Dipole

Any molecule or radical that has delocalised positive and negative charges

Hydrogen bonds

It is formed when a hydrogen atom, already covalently linked to one electronegative atom (usually nitrogen or oxygen), is attracted by another electron-hungry atom, so that a “bridge” forms between them.

surface tension

water molecules to cling together and form films

intramolecular bonds

Although hydrogen bonds are too weak to bind atoms together to form molecules, they are important \___________, which hold different parts of a single large molecule in a specific three-dimensional shape.

Chemical Reaction

It occurs whenever chemical bonds are formed, rearranged, or broken.

subscript

A number written as a \____ indicates that the atoms are joined by chemical bonds.

prefix

a number written as a \______ denotes the number of unjoined atoms or molecules.

Synthesis Reaction

Also known as a Combination reaction, it occurs when atoms or molecules combine to form a larger, more complex molecule.

Decomposition Reaction

This occurs when a molecule is broken down into smaller molecules or its constituent atoms.

Exchange Reaction

Also known as the displacement reaction, it involve both synthesis and decomposition.

Oxidation-Reduction Reaction

Here, electrons are exchanged between the reactants. This reaction also occurs when the ionic compound is formed.

Electron donors

reactant losing the electrons; is said to be oxidised.

Electron acceptors

reactant taking up the transferred electrons; is said to be reduced.

Cellular Respiration

A series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body.

Exergonic reactions

Reactions that release energy.

Endergonic reactions

Reactions that absorb energy.

chemical equilibrium

When the arrows are of equal length, as in neither the forward reaction nor the reverse reaction is dominant

net change

Once chemical equilibrium is reached, there is no further \______ in the amounts of reactants and products unless more of either are added to the mix.

Catalysts

These are substances that increase the rate of chemical reactions without themselves becoming chemically changed or part of the product.

Enzymes

Biological catalysts.

Biochemistry

The study of the chemical composition and reactions of living matter.

Organic compounds

Substances that contain carbon.

Inorganic compounds

Any substance in which two or more chemical elements are combined.

Hydration layers

Layers of water molecules which water forms around large charged molecules.

Hydrolysis reactions

Involves adding water to one large molecule to break it into multiple smaller molecules.

Dehydration synthesis

A reaction when a water molecule is removed for every bond formed.

Salt

An ionic compound containing cations other than H+ and anions other than the hydroxyl ion (OH-)

Polyatomic ions

Groups of atoms that bear an overall charge.

Calcium phosphates

salts that make bones and teeth hard.

Acids

Substances that releases hydrogen ions (H+) in detectable amounts. Proton donors.

Bases

Substances that take up hydrogen ions in detectable amounts. Proton acceptors.

Bicarbonate ion

an important base in the body, is particularly abundant in blood.

Ammonia

a common waste product of protein breakdown in the body, is also a base.

pH units

Concentration units that measures relative concentration of hydrogen ions in various body fluids.

Sören Sörensen

He devised the pH scale in 1909.

Neutralization reaction

A reaction when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water.

Buffers

A solution that can resist pH change upon the addition of an acidic or basic components

Strong acids

Acids that dissociate completely and irreversibly in water.

Weak acids

Acids that do not dissociate completely.

Strong bases

Bases that dissociate easily in water and quickly tie up H+.

Weak bases

Bases that do not completely dissociate into their constituent ions when dissolved in solutions.

Polymers

Chainlike molecules made of many similar or repeating units which are joined together by dehydration synthesis.