Chapter 2: The Chemistry of Life
Section 1: The Nature of Matter
CCS Biology
Mr. Bogusch
Atoms
Atoms – basic units of matter
Atoms are made of three parts
Proton – positively charged
subatomic particle
Neutron – subatomic particle with
no charge
Electron – negatively charged
subatomic particle
1/1840 mass of a proton
An atoms positive and negative
charges even each other out
which make the atom neutral
Atomic Models
Elements and Isotopes
Elements – pure substance that consist entirely of only
one type of atom
Atomic number – number of protons
More than 100 elements are known and organized on
the periodic table
Interactive Periodic Table of Elements
Elements and Isotopes
Isotope – atom of the same
element that have different
number of neutrons
Mass Number – total number
of protons and neutrons
Radioactive Isotope – nuclei are
unstable and break down at a
constant rate over time.
Uses
Radiometric dating
Detect and treat cancer
Chemical Compounds
Compound – substance
formed by the chemical
combination of two or
more elements in definite
proportions
Chemical Formula
Examples
NaCL, H2O
Chemical Compounds
The characteristics of compounds
are usually different form the
individual elements it is made of
For Example
H2O – Water – if you combine
hydrogen gas and oxygen gas it can be
explosive!
NaCl – Salt – sodium chloride – salt is
essential to all living things
Hydrogen and Oxygen Balloons
Sodium and Water
Na – Sodium – silver colored metal
soft enough to cut with a knife that
reacts explosively with water
Cl – Chlorine – poisonous gas
used in WWI – chemical warfare
Chemical Bonds
Ionic Bond – formed when 2 or more electrons are transferred from
one atom to another
Ions – atoms that gain or lose an electron
For example
Na+ + Cl --- → NaCl
Positively charged + negatively charged = neutral charge
Ionic Bonding - NaCl
Chemical Bonds
Covalent Bond – formed when atoms share electrons
Molecule – atoms joined together by covalent bonds
For example: H2O
Chemical Bonds
Van der Waals Forces – a weak chemical attraction
between oppositely charged regions of nearby molecules
For Example: H2O, Tokay gecko
Chapter 2: The Chemistry of Life
Section 2: Properties of Water
The Water Molecule
Found in liquid form over most
of the Earth’s surface
Like most molecules, Water is
neutral
H2O has 10 protons
(positive) and 10 electrons
(negative)
The protons and
electrons balance each
other out!
The Water Molecule
Polarity – a molecular with an uneven distribution of charge
Oxygen has 8 protons which attract electrons strongly, as a result
most of water electrons are found near the oxygen atom making
that side of the atom partially negative charged
The Water Molecule
Hydrogen Bonding - that attraction
between a hydrogen atom with a
partially positive charge with another
atom with a partial negative charge
Because of their partial positive
and negative charges, polar
molecules can attract each other.
Because water is a polar
molecule, it is able to form
multiple hydrogen bonds, which
account for many of water’s
special properties.
The Water Molecule
The Water Molecule
Cohesion –attraction between molecules of the same substance
Water can attract itself forming “beads” of water
Cohesion also produces surface tension
Water molecules hydrogen bonds have a certain amount of
strength
For example – spiders that can walk on water
Cohesion and Adhesion
The Water Molecule
Adhesion – the attraction between molecules of different substances
For example: water on glass
The Water Molecule
Heat Capacity
Since there are multiple hydrogen bonds between water
molecules it takes a large amount of energy to cause those
molecules to move fast, which raises the temperature.
For example: large lakes and oceans retain heat even though the
air will become colder. This protects against drastic change in
temperature
Solutions and Suspensions
Mixture – a material composed of two or more elements or
compounds that are physically mixed together but not chemically
combined.
Solutions and Suspensions
Two types of mixtures that re combined with water are solutions and
suspensions
Solutions- a substance that is evenly distributed in water
Solute – the substance that is dissolved
Solvent (water)– the substance in which the solute dissolves
Water’s polarity gives it the ability to dissolve both ionic and
other polar molecules
Suspension – mixtures of water and nondissolved material
Acids, Bases, and pH
Water molecules split to form ions
pH Scale – indicates the concentration of H+ ions in a solution
Range 0 – 14
Acids < pH of 7 (contain a high concentration of H+ ions)
Bases > pH of 7 ( contain a high concentration of OH- ions and
a low concentration of H+ ions)
Neutral = 7 (contain no H+ ions or OH- ions “theoretically”)
Acids, Bases, and pH