CH. 2 Chemistry of life
Section 1 Nature of matter
Atoms
• Atom- is the smallest unit of
matter that cannot be broken
down by chemical means.
• Atoms consist of 3 kinds of
particles: electrons, protons and
neutrons.
CH. 2 Chemistry of life
Section 1 Nature of matter
Electron, protons, and Neutrons
• Electrons have a negative charge (-), and
are located outside the nucleus in the
electron cloud.
• Protons have a positive charge (+), and
are located in the nucleus or core of an
atom.
• Neutrons have no charge, located in the
nucleus or core of an atom.
CH. 2 Chemistry of life
Section 1 Nature of matter
Electrons, Protons, and Neutrons
• Because electrons have a negative chare
the electron cloud of an atom is always
negative
• Because protons are positive and
neutrons are neutral the nucleus of an
atom is always positive.
• Because electrons and protons are
oppositely charged they attract one
another.
CH. 2 Chemistry of life
Section 1 Nature of matter
Elements
• Element- a pure substance made of only
one kind of atom.
• There are more than 100 known
elements, and each is represented by a
one, two, or three letter symbol. Ex.
Hydrogen (H) Carbon (C).
• Elements differ in the number of
protons their atoms contain.
CH. 2 Chemistry of life
Section 1 Nature of matter
Chemical Bonding
• Atoms can join with other atoms to form
stable substances.
• A force that joins atoms is called a
chemical bond.
• compound-a substance made of the
joined atoms of two or more different
elements.
CH. 2 Chemistry of life
Section 1 Nature of matter
Covalent Bonds
• Molecule-smallest unit of a substance that
keeps all of the properties of that substance;
it can consist of one atom or two or more
atoms bonded together.
• Covalent bonds form when two or more
atoms share electrons to form a molecule.
• A molecule such as the water molecule
shown below, is a group of atoms held
together by covalent bonds.
CH. 2 Chemistry of life
Section 1 Nature of matter
Covalent Bonds
• The arrangement of their electrons
determines how atoms bond together.
• An atom becomes stable when its outer
electron level is full. If the outer electron
level is not full, an atom will react
readily with atoms that can provide
electrons to fill its outer level.
CH. 2 Chemistry of life
Section 1 Nature of matter
Ionic Bonds
• Sometimes atoms or molecules gain or lose
electrons.
• Ion-An atom or molecule that has gained or
lost one or more electrons.
• Ions have an electrical charge because they
contain an unequal number of electrons and
protons. Ions of opposite charge may
interact to form an ionic bond.
Ch. 2 Chemistry of life
Section 2 Water and
solutions
CH. 2 Chemistry of life
Section 2 Water and solutions
Water in living things
•70 % of your body is made
up of water.
•2/3 of molecules in your
body are water molecules.
CH. 2 Chemistry of life
Section 2 Water and solutions
Storage of Energy
• Many organisms release excess heat through
water evaporation.
• In organisms, this ability to control
temperature enables cells to maintain a
constant internal temperature when the
external temperature changes.
• In this way, water helps cells maintain
homeostasis.
CH. 2 Chemistry of life
Section 2 Water and solutions
Cohesion and Adhesion
• Cohesion-is an attraction between substances of
the same kind.
• Because of cohesion, water and other liquids form
thin films and drops.
• Molecules at the surface of water are linked
together by hydrogen bonds like a crowd of people
linked by holding hands. This attraction between
water molecules causes a condition known as
surface tension.
CH. 2 Chemistry of life
Section 2 Water and solutions
Cohesion and Adhesion
• Adhesion-is an attraction between different
substances.
Aqueous Solutions
• Solution-a mixture in which one or more substances
are evenly distributed in another substance.
• Substances can dissolve in water, they can more
easily move within and between cells.
CH. 2 Chemistry of life
Section 2 Water and solutions
Polarity
• The polarity of water enables many substances to
dissolve in water.
• When ionic compounds dissolve in water ions
become surrounded by polar water molecules.
• The resulting solution is a mixture of water
molecules and ions.
• Nonpolar molecules do not dissolve well in water.
CH. 2 Chemistry of life
Section 2 Water and solutions
Acids and Bases
• Acids-compounds that from hydrogen ions when
dissolved in water.
• When an acid is added to water, the concentration
of hydrogen ions in the solution is increased above
that of pure water.
• Bases-compounds that reduce the concentration of
hydrogen ions in a solution.
• The pH scale measures the concentration of
hydrogen ions in a solution.
Chapter 2 Chemistry
of life
Section 3 Chemistry of
cells
CH. 2 Chemistry of life
Section 3 Chemistry of cells
Carbon Compounds
• Four principal classes of organic compounds
are found in living things: Carbohydrates,
lipids, proteins, and nucleic acids.
• Without these compounds cells could not
function.
CH. 2 Chemistry of life
Section 3 Chemistry of cells
Carbohydrates