This document provides an overview of chemistry concepts including: - Matter is anything that occupies space and has mass. Atoms are the smallest particle of an element and consist of protons, neutrons, and electrons. - Elements combine in fixed proportions to form compounds. Chemical reactions involve breaking and forming bonds to create new substances. - Living things require energy, obtained through exergonic reactions like cellular respiration. Catalysts like enzymes lower reaction activation energies. - Solutions are uniform mixtures where particles of solute are distributed within a solvent. Aqueous solutions in living things are important for biochemical reactions. Acids and bases are defined by hydronium and hydroxide ion concentrations measured on the pH scale.

1. CHEMISTRY

2. Composition of Matter
 Matter - Everything in
universe is composed of
matter
 Matter is anything that
occupies space or has
mass
Mass – quantity of
matter an object has
Weight – pull of
gravity on an object

3. Elements
 Pure substances that cannot be broken
down chemically into simpler kinds of
matter
 More than 100 elements (92 naturally
occurring)

4.  90% of the mass of an
organism is composed of 4
elements (oxygen, carbon,
hydrogen and nitrogen)
 Each element unique
chemical symbol
 Consists of 1-2 letters
 First letter is always
capitalized

5. Atoms
 The simplest particle of
an element that retains
all the properties of that
element
 Properties of atoms
determine the structure
and properties of the
matter they compose
 Our understanding of the
structure of atoms based
on scientific models, not
observation

6. The Nucleus
 Central core
 Consists of positive
charged protons
and neutral
neutrons
 Positively charged
 Contains most of
the mass of the
atom

7. The Protons
 All atoms of a given element have the
same number of protons
 Number of protons called the atomic
number
 Number of protons balanced by an equal
number of negatively charged electrons

8. The Neutrons
 The number varies slightly among atoms
of the same element
 Different number of neutrons produces
isotopes of the same element

9. Atomic Mass
 Protons & neutrons are found in the
nucleus of an atom
 Protons and neutrons each have a
mass of 1 amu (atomic mass unit)
 The atomic mass of an atom is found
by adding the number of protons &
neutrons in an atom

10. The Electrons
 Negatively charged high energy particles
with little or no mass
 Travel at very high speeds at various
distances (energy levels) from the
nucleus

11.  Electrons in the same energy level
are approximately the same distance
from the nucleus
 Outer energy levels have more
energy than inner levels
 Each level holds only a certain
number of electrons

12. Energy Levels
 Atoms have 7 energy levels
 The levels are K (closest to the
nucleus), L, M, N, O, P, Q
(furthest from the nucleus)
 The K level can only hold 2
electrons
 Levels L – Q can hold 8 electrons
(octet rule)

13. Periodic Table
 Elements are arranged by their
atomic number on the Periodic Table
 The horizontal rows are called
Periods & tell the number of
energy levels
 Vertical groups are called Families &
tell the outermost number of
electrons

15. Compounds
 Most
elements do
not exist by
themselves
 Readily
combine with
other
elements in
a
predictable
fashion

16.  A compound is a pure
substance made up of
atoms of two or more
elements
 The proportion of
atoms are always
fixed
 Chemical formula shows
the kind and proportion
of atoms of each
element that occurs in a
particular compound

17.  Molecules are the
simplest part of
a substance that
retains all of the
properties of the
substance and
exists in a free
state
 Some molecules
are large and
complex

18. Chemical Formulas
 Subscript after a symbol tell the
number of atoms of each element
 H20 has 2 atoms of hydrogen & 1
atom of oxygen
 Coefficients before a formula tell
the number of molecules
 3O2 represents 3 molecules of oxygen
or (3x2) or 6 atoms of oxygen

19.  The physical
and chemical
properties of
a compound
differ from
the physical
and chemical
properties of
the individual
elements that
compose it

20.  The tendency of
elements to combine
and form compounds
depends on the number
and arrangement of
electrons in their
outermost energy level
 Atoms are most stable
when their outer most
energy level is filled

21.  Most atoms are not stable
in their natural state
 Tend to react (combine)
with other atoms in order
to become more stable
(undergo chemical
reactions)
 In chemical reactions
bonds are broken; atoms
rearranged and new
chemical bonds are
formed that store energy

22. Covalent Bonds
 Formed when two atoms share one or
more pairs of electrons

23. Ionic Bonds
 Some atoms become stable by losing or
gaining electrons
 Atoms that lose electrons are called
positive ions

24.  Atoms that gain electrons are called
negative ions
 Because positive and negative electrical
charges attract each other ionic bonds
form

25. Energy and Matter
 Energy
 The ability to do work or cause
change
 Occurs in various forms
 Can be converted to another form
 Forms important to biological
systems are chemical, thermal,
electrical and mechanical energy
 Free energy is the energy in a
system that is available for work

26. States of Matter
 Atoms are in constant motion
 The rate at which atoms or molecules in
a substance move determines its state

27.  Solid
Molecules tightly linked together in
a definite shape
Vibrate in place
Fixed volume and shape

28.  Liquids
Molecules not as tightly linked
as a solid
Maintain fixed volume
Able to flow and conform to
shape of container

29. Gas
 Molecules have little
or no attraction to each
other
 Fill the volume of the
occupied container
 Move most rapidly
 To cause a substance to
change state, thermal energy
(heat) must be added to or
removed from a substance

30. Energy and Chemical Reactions
 Living things
undergo
thousands of
chemical
reactions as part
of the life
process

31.  Many are very complex
involving multistep
sequences called
biochemical pathways
 Chemical equations
represent chemical
reactions
 Reactants are shown on the
left side of the equation
 Products are shown on the
right side

32.  The number of
each kind of atom
must be the same
on either side of
the arrow
(equation must be
balanced)
 Bonds may be
broken or made
forming new
compounds

33. Energy Transfer
 Much of the energy
organisms need is
provided by sugar (food)
 Undergoes a series of
chemical reactions in
which energy is released
(cell respiration)
 The net release of free
energy is called an
exergonic (exothermic)
reaction

34.  Reactions that involve
a net absorption of
free energy are called
endergonic
(endothermic)
reactions
 Photosynthesis is an
example
 Most reactions in living
organisms are
endergonic; therefore
living organisms
require a constant
source of energy

35.  Most chemical reactions require energy
to begin
 The amount of energy needed to start
the reaction is called activation energy

36.  Certain
chemical
substances
(catalysts)
reduce the
amount of
activation
energy
required
 Biological
catalysts are
called enzymes

37.  Enzymes are an important class of
catalysts in living organisms
 Mostly protein
 Thousands of different kinds
 Each specific for a different
chemical reaction

38. Enzyme Structure
 Enzymes work on
substances called
substrates
 Substrates must fit
into a place on an
enzyme called the
active site
 Enzymes are reusable!

39. Reduction-Oxidation Reactions
 Many of the chemical reactions that
help transfer energy in living organisms
involve the transfer of electrons
(reduction-oxidation = redox reactions)

40.  Oxidation reaction – reactant loses
electron(s) becoming more positive

41.  Reduction reaction – reactant gains
electron(s) becoming more negative

42. Solutions

43. Solutions
 A solution is a
mixture in
which 2 or
more
substances are
uniformly
distributed in
another
substance

44.  Solute is the
substance
dissolved in the
solution
 Particles may
be ions, atoms,
or molecules
 Solvent is the
substance in which
the solute is
dissolved
 Water is the
universal solvent

45.  Solutions can be composed
of varying proportions of a
given solute in a given
solvent --- vary in
concentration (measurement
of the amount of solute)
 A saturated solution is one
in which no more solute can
be dissolved
 Aqueous solution (water) are
universally important to
living things

46.  Dissociation of water
 Breaking apart of the
water molecule into two
ions of opposite charge
(due to strong
attraction of oxygen
atom of one molecule
for H atom of another
water molecule)
 H2O  H+ (hydrogen
ion) + OH- (hydroxide
ion)
 H+ + H2O  H3O
(hydronium ion)

47. Acids and Bases
 One of the most important aspects of a
living system is the degree of acidity or
alkalinity

48. Acids
 Number of hydronium ions in solutions is
greater than the number of hydroxide
ions
HCl  H+ + Cl-

49. Bases
 Number of hydroxide ions in solution is
greater than the number of hydronium
ions
NaOH  Na+ + OH-

50. pH Scale
 logarithmic
scale for
comparing the
relative
concentrations
of hydronium
ions and
hydroxide ions
in a solution
 ranges from 0
to 14
 Each pH is 10X
stronger than next
 e.g. ph 1 is 10 times
stronger than ph 2

51.  the lower the pH the stronger the acid
 the higher the pH the stronger the base
 pH 7.0 is neutral

52. Buffers
 Control of pH is very
important
 Most enzymes function
only within a very
narrow pH
 Control is accomplished
with buffers made by
the body
 Buffers keep a neutral
pH (pH 7)

53.  Buffers neutralize
small amounts of
either an acid or
base added to a
solution
 Complex buffering
systems maintain
the pH values of
your body’s many
fluids at normal and
safe levels