Transcript Chapter 3 Chemistry of Life

Atom
• Basic unit of matter
Subatomic particles
• Protons - Positively charged (+)
• Neutrons - Not charged (neutral)
• Electrons - Negatively charged (-)
Electrons
Bind together
to form the
nucleus
Protons
Nucleus
Neutrons
Element
• A pure substance that consists
of just one type of atom
An elements atomic number = number of
protons
6
C
Carbon
12.011
Atomic number
Isotope
• Atoms of the same element
that differ in the number of
neutrons they contain
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
The Sum of protons and neutrons in the nucleus of an
atom is its mass number
6
C
Carbon
12.011
Mass number
Atomic Mass
• The weighted average of the
masses of an elements isotope is
called its atomic mass
Radioactive isotopes
• Can be dangerous
• Can be used
practically
–Radioactive dating
–Treat cancer
–Kill bacteria
Compounds
• A substance formed by the
chemical combination of two or
more elements in definite
proportions
• Ex) H2O, NaCl
Table Salt
Ionic Bonds
• Formed when one or more
electrons are transferred from
one atom to another
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
• If an atom loses an electron it
becomes positive
• Ex: All metals
• If an atom gains an electron it
becomes negative
• Ex:All nonmetals
Ions
• Positively and negatively
charged atoms
Covalent Bonds
• Forms when electrons are
shared between atoms
Molecule
• The structure that results when
atoms are joined together by a
covalent bond
• Both elements are nonmetals
• Smallest unit of most compounds
Van der Waals Forces
• A slight attraction that
develops between the
oppositely charged regions of
nearby molecules due to
unequal sharing of electrons
Homework
Questions and Answers
1. Describe the structure of an atom.
Atoms are made up of protons and
neutrons in a nucleus. Electrons are
in constant motion in the space
around the nucleus.
2. Why do all isotopes of an element
have the same chemical properties
They have the same number of
electrons
3. What is a covalent bond?
A bond formed when electrons are
shared between atoms
4. What is a compound? How are they
related to molecules
A compound is a substance formed
by the chemical combination of two or
more elements in definite proportions.
A molecule is the smallest unit of
most compounds
5. How do Van der Waals forces
hold molecules together?
When the sharing of electrons
are unequal, a molecule has
regions that are charged. An
attraction can occur between
oppositely charged regions of
nearby molecules
6. How are ionic bonds and Van
der Waals forces similar? How
are they different?
In both cases, particles are
held together by attractions
between opposite charges.
The difference is that ionic
charges are stronger
Section 2: Properties of
Water
Objectives
• Why are water molecules polar?
• What are acidic solutions? What
are basic solutions?
Basic information about water
•
Formula for water: H2O
•
Structure of a water molecule:
•
•
The solid lines between the O and the H
represent covalent bonds
In covalent bonds, electrons between
the atoms are shared.
• In some kinds of molecules, the
electrons
•
are shared equally between two
atoms.
6. We say that those are nonpolar
covalent bonds.
•
In water, though, oxygen and hydrogen
do NOT share their electrons equally with each
other so we say that there is a polar covalent
bond between them.
•
Because the oxygen atom is
pulling negative charges
toward itself, this makes
oxygen take on a partial
negative charge.
• 9. The hydrogen atom is having negative
•
•
•
electrons pulled away from it, so the
2 hydrogen atoms will take on a partial
positive charge.
•
When another water molecule comes in, the
partial negative oxygen of one water molecule will
hydrogen bond with the partial positive hydrogen
of another water molecule.
• 11. Hydrogen bonds are very weak, but
•
they are very important in molecules like DNA and
proteins.
• Hydrogen bonds are also responsible for
the many properties of water, such as:
A. Cohesion:
the attraction of molecules of the same kind
(water molecules to
other water molecules)
B. Adhesion: the attraction among
molecules of different substances
(water molecule to something else)
The Big Idea
• Much of our planet is covered in
water
• Water is necessary for life to exist
• If life exists on other planets,
there most likely is water present
• Water has many properties that
make life possible
Polarity
(-)
The oxygen atom has
a stronger attraction for
electrons
(+)
Hydrogen Bonds
• Because of waters partial
charges, they can attract each
other and create hydrogen bonds
• Not as strong as covalent or ionic
bonds
• Waters ability to create multiple
hydrogen bonds gives it many
special properties
Cohesion
• Attraction between molecules of
the same substance
Adhesion
• Attraction molecules of different
substances
Mixture
• Material composed of two or more
elements or compounds that are
physically mixed but not
chemically combined
• Ex.) salt & pepper, earths
atmosphere
Solutions
• Mixture of two or more
substances in which the
molecules are evenly distributed
• Ex.) salt water
• Settles out over time
Solutions
Cl-
Cl-
Na+
Na+
Water
Water
Solute
• Substance that is dissolved
• Ex.) salt
Solvent
• The substance that does the
dissolving
• Ex.) Water
Suspensions
• Mixture of water and nondissolved materials
• Separate into pieces so small,
they never settle out
• Ex: water and oil
Types of solutions
• A dilute solution is weak solution
• A concentrated solution is strong.
• An unsaturated solution contains less
dissolved solute than it can hold at a given
temp.
• A saturated solution contains all of the
solute it can hold at a given temp.
• A Super saturated solution containing more
solute than it can normally hold at a given
temp.
( Crystals are often seen in this type of
solution).
What is the pH scale?
• measure of the concentration of
hydrogen ions in a solution
• Always shows reading between 0-14
• pH between 0-7 is an acid
• pH between 7-14 is a base
• pH 7 is neutral.
• neutral: neither acidic nor basic
What is an acid?
*Tastes sour
*Conducts electricity
*Corrosive to skin
*Can eat through metal
*Formulas starts with “H”
*Always releases hydrogen ions (H+)
when dissolved in water
*pH is between 0-7
What is a base?
*Tastes
Bitter
*Conducts electricity
*Corrosive to skin
*Feel slippery
*Formulas ends with “OH”
*Always releases hydroxide ions
(OH¯) when dissolved in water
*Red litmus paper into Blue
(indicator)
*pH between 7-14
What are indicators?
• substance that changes color in an
acid or a base
What is neutralization?
• reaction between an acid and a base to
produce a salt and water
What is an electrolyte?
• electrolyte : substance that conducts an
electric current when it is dissolved in
water
• ionization : formation of ions
• Nonelectrolyte: substance that will not
conduct an electric current when it is
dissolved in water .
Acid
Neutral
Base
Buffers
• Weak acids or bases that can
react with strong acids or bases
to prevent sharp, sudden pH
changes
Homework
Questions and Answers
1. Use the structure of a water
molecule to explain why its polar
Oxygen atom has greater
attraction for electrons, therefore
the oxygen atom is negative and
the hydrogen end is positive
2. Compare acidic and basic
solutions in terms of their H+ ion
and OH- ion concentrations
Acid have more H+ ions than OHions, and bases have more OHions than H+ ions
3. What is the difference between a
solution and a suspension?
In a solution, all components are
evenly distributed. In a
suspension, un-dissolved
particles are suspended
4. What does pH measure?
The concentration of H+ ions in a
solution
5. The strong acid hydrogen floride
(HF) can be dissolved in pure
water. Will the pH of the solution
be greater or less than 7?
less than 7
Section 3: Carbon Compounds
Objective
• What are the functions of each
group of organic compounds?
Interest Grabber
Section 2-3
Life’s backbone
• Most of the compounds that make up living
things contain carbon. In fact, carbon makes
up the basic structure, or “backbone,” of these
compounds. Each atom of carbon has four
electrons in its outer energy level, which
makes it possible for each carbon atom to
form four bonds with other atoms.
• As a result, carbon atoms can form long
chains. A huge number of different carbon
compounds exist. Each compound has a
different structure. For example, carbon chains
can be straight or branching. Also, other kinds
of atoms can be attached to the carbon chain.
Methane
Acetylene
Butadiene
Benzene
Isooctane
Macromolecules “giant molecules”
• Formed by a process called
polymerization
Monomers
• Smaller units
Polymers
• Linked up monomers
Carbohydrates
• Compounds made up of carbon,
hydrogen, and oxygen atoms
usually in a ratio of 1:2:1
• Main source of energy
• The monomers of starch are
sugars
• Single sugar molecules are called
monosaccharides
• The large macromolecules
formed from monosaccharides
are known as polysaccharides
Starch
Glucose
Lipids
• Made mostly from carbon and
hydrogen atoms
• Used to store energy
Lipid
Fatty Acids
Glycerol
Proteins
• Macromolecules that contain
nitrogen as well as carbon,
hydrogen, and oxygen
• Proteins are polymers of
molecules called amino acids
Amino Acids
Carboxyl group
General structure
Alanine
Serine
• More than 20 different amino
acids, can join to any other amino
acid
• The instructions for arranging
amino acids into many different
proteins are stored in DNA
• Each protein has a specific role
• The shape of proteins can be very
important
Proteins
Amino
Acids
Nucleic Acids
• Macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and
phosphorus
Double
Helix
Nucleotides
• Consists of 3 parts: 5-carbon sugar,
phosphate group and nitrogen base
Nitrogen Base
Phosphate
group
5-Carbon Sugar
2 kinds of nucleic acids
• RNA (ribonucleic acids) –
contains sugar ribose
• DNA (deoxyribonucleic acid) –
contains sugar deoxyribose
Homework
Questions and Answers
1. Name four groups of organic compounds
found in living things
carbohydrate, lipid, protein, nucleic acids
2. Describe at least one function of each
group of organic compounds
carbohydrates – energy
lipids – store energy
proteins – form tissue
nucleic acids – transmit hereditary
information
3. Compare the structures and
functions of lipids and starches
Lipids are made from carbon and
hydrogen. Starches are made of
carbon, hydrogen and oxygen.
They both can be used to store
energy