Notes 2.2

Chapter 2 The Chemical Basis of Life 

Matter – 

anything that contains mass and occupies space

Atoms – 

smallest functional units of matter that form all chemical substances and ultimately all organisms. 

Molecules –

 two or more atoms bonded together

Element – 

a pure substance of only one kind of atom

Atomic nucleus – 

the small dense “middle” of the atom where most of the atom mass is found.

*Dissuss the gold foil experiment pg.22-23

Orbitals – 

the region of space surrounding the nucleus in which there is a high probability of finding that electron

*remember cars on a road.

Energy shells – 

energy levels(The distinct areas that electrons of found as you move out from the nucleus.)

Energy – 

the capacity to do work or effect a change

Valence electrons – 

electrons in the outermost shell 

* These are the electrons involved in bond formation.

Atomic number – 

the number of protons in an atom

Atomic mass – 

scale indicates an atom’s mass relative to the mass of other atoms

Dalton (Da) – 

also known as an atomic mass unit (amu), equals 1/12 the mass of a carbon-12 atom, or about the mass of a proton or a hydrogen atom

Mole – 

contains the same number of particles as there are atoms in exactly 12 g of carbon

Avogadro’s number-(6.02 x 1023 atoms) The number of particles found in a mole.

*Read example pg.26

Isotopes-

Atoms of the same element with different number of neutrons.

Radioisotopes-

Unstable isotopes that lose energy by emitting subatomic particles and/or radiation.

• Typically oxygen, carbon, hydrogen, and nitrogen make up 95% of the mass of living organisms. 

Trace elements-

Elements that are only needed in small amounts, but are very essential for normal growth and function.

*Table 2.2 on page 27

Molecular formula- 

The number (s) and letter(s) that represent a molecule.

Compound- 

Molecule composed of two or more different elements.

Covalent Bonds-

 compounds in which valence electrons are shared.

Octet Rule- 

a fundamental principle that atoms are stable when they have eight electrons in their outer shell.

Double bond- 

Two shared pairs of electrons are involved in a bond.

Electronegativity-

 The measure of an atoms ability to attract electrons in a bond with another atom.

Polar Covalent Bonds- 

an uneven distribution of electrons around the nucleus causes a (polarity) difference in electric charge. 

Nonpolar covalent bonds- 

A relatively even distribution of electrons around the nucleus, because the atom on the bond have similar electronegativities. 

Polar molecules- 

molecules with many polar bonds.

Nonpolar molecules- 

Molecules with predominantly nonpolar bonds. 

Hydrogen bonds- 

A weak bond formed as the hydrogen atom in one molecule becomes electrically attracted to an electronegative atom in another molecule. Ex. H20

Enzymes-

proteins that serve as a catalyst

Van der Waals forces- 

a special class of bonds that exhibit a weak attraction(many H bonds)

Ions- 

charged particles

Cations –

positively charged particles

Anions- 

negatively charged particles

Ionic Bond- 

formed as a cation and anion are attracted to one another

Free radicals- 

a molecule containing an atom with a single unpaired electron in its outer shell

*These free radicals may steal electrons from other atoms

* These free radicals can be used to kill bacteria

* These also attack body cells

*Antioxidants (vitamin C and vitamin E) are found in fruits and vegetables

Chemical reaction – 

results when 1 or more substances are changed into other substances

Reactants- 

The beginning substances in a chemical reaction

Products- 

The ending substances in a chemical reaction

Chemical equilibrium-

The point at which the rate of forward movement in a reaction is equal to the backwards movement in the chemical reaction

Solutes- 

Substance being dissolved

Solvents- 

Substance doing the dissolving

Solution- 

the new substance formed as the solutes and solvents are mixed

Aqueous solutions- 

solutions made with water

Hydrophilic- 

substance that dissolve in water (ionic or polar covalent)

Hydrophobic- 

substances that do not dissolve in water (non-polar)

*Talk about cell membrane*

Amphipathic- 

Molecules with polar and nonpolar regions

Micelles-(p. 35)

spheres formed from long amphipathic molecules

*nonpolar inside and polar end outside*

Concentrations- 

amount of solute/unit volume

Molecular mass-

the sum of the atomic masses in the molecule

Molarity-

the number of moles of a solute in lL of solution

Molar-

the label for molarity

Heat of vaporization of water- 

the energy required to change one mole of liquid into a vapor at the substances boiling point

Heat of fusion- 

the energy released as one mole of a substances changes to liquid

Colligative properties- 

the qualities of a solution that depend strictly on the number of dissolved solutes

Lower the freezing point

Raises the boiling point

Lowers the vapor pressure

Hydrolysis- 

a process in which water is broken apart

Condensation reaction- 

a process in which two molecules combine to form a larger molecule and a smaller molecule

Dehydration reaction- 

a condensation reaction in which water is formed

Evaporation- 

the conversion of a liquid to a gas below the boiling point

Specific Heat- 

the amount of energy needed to raise 1 gram of a substance 1 degree C

Cohesion- 

the phenomenon of water molecules sticking to each other

Adhesion- 

the phenomenon of water molecules sticking to some other substance

Surface tension- 

a measure of the attraction between molecules at the surface of a liquid

Hydroxide ion- OH –ions

Hydronium ions – H+ ions

Acids- 

substances releasing H+ ions in a solution

Strong acids- 

acids completely or mostly ionized when dissolved in water

Weak acids- 

acids that barely ionize when dissolved in water

Bases- 

substances that absorb H+ when dissolved in a solution

pH- 

the H+ concentration expressed as the negative logarithm to the base 10

Acidic- 

a substance with a pH below 7

Alkaline(Basic)-

 a substance with a pH above 7

Group question – 

Buffer- 

a substance that resists the change of pH. (weak acid and its conjugate base)

*Look at p. 40*  cells 6.5-7.8

              Blood 7.35-7.45