Transcript Unit 4: General Chemistry

Matter and its properties
OBJ: Distinguish among atoms, elements, compounds,
and molecules
The Atom
 Basic unit of matter
 Made up of protons,
neutrons, electrons
Atom: Subatomic particles
 Nucleus: protons (+)
and neutrons (0) bind
together at the center
of the atom
 Electrons: negatively
charged particle;
constantly moving
around the nucleus
Elements
 Pure substance
 Consists of one type of atom
 Atomic Number
= Proton #,
electron #
 Atomic Mass =
protons +
neutrons
Main Elements in Living Things
 Carbon (C)
 Hydrogen (H)
 Oxygen (O)
 Nitrogen (N)
 We also need: phosphorus and sulfer
Isotopes
 When an element has different number of neutrons
 Example: Carbon normally has 6; a carbon isotope
would have 8 neutrons
 Isotopes have similar chemical properties because they
have the same # of electrons
Radioactive Isotopes
 Some isotopes are unstable – their nuclei break down
over a period of time
 Radioactive dating
 Can be used to determine ages of rocks and fossils
 Radiation from certain isotopes have help treat cancer
Compounds and Molecules
 Chemical combination of two or more elements
 Example: H2O, NaCl
 Elements that make up a compound can be very
different from the actual compound (ie: oxygen is a gas
at room temperature)
 Molecule= smallest unit of compounds
Practice using Periodic Table
Homework
 Pick 5 elements from the Periodic Table and identify
the following:
 Name
 Atomic Number
 Atomic Mass
 Number of protons, neutrons, electrons
OBJ: Describe the structure of an atom and the role of
electrons in bonding
Electrons
 Bond formation involves the
electrons that surround each
atomic nucleus
 Valence electrons =
electrons available to form
bonds
Chemical Bonds
Ionic Bonds
Covalent Bonds
 When one or more electrons
 When electrons are shared
are transferred from one atom
to another
between atoms
 Form Molecules
Chemical Bonds
Ionic Bonds
Covalent Bonds
 When one or more electrons
 When electrons are shared
are transferred from one atom
to another
between atoms
 Form Molecules
Chemical Bonds
Ionic Bonds
Covalent Bonds
 When one or more electrons
 When electrons are shared
are transferred from one atom
to another
between atoms
 Form Molecules
Chemical Equations
 http://youtu.be/dExpJAECSL8
Homework:
 Cayan Biology Flexbook
 Chemical Bonding Chapter
 Practice Questions 1-6
OBJ: DESCRIBE THE PROPERTIES OF WATER THAT
MAKE IT A UNIQUE SUBSTANCE NECESSARY FOR
LIFE.
The Water Molecule
 Oxygen end of molecule has a
slightly negative charge
 Hydrogen end of molecule has a
slightly positive charge
 Polar molecule: uneven
distribution of electrons between
the oxygen and hydrogen atoms
Poles of the Water Molecule
Hydrogen Bonds
 Not very strong
 Between two water
molecules
 Water molecules can
have multiple hydrogen
bonds
Cohesion
 Attraction between
molecules of the same
substance
 Water is cohesive due to
hydrogen bonding
 Responsible for surface
tension
Adhesion
 Attraction between molecules of
different substances
 Example: water molecules and
glass molecules cause water to
rise around the graduated
cylinders
Properties of Water
 Polarity
 Cohesion
 Adhesion
 Surface tension
 Hydrophobic
 Hydrophilic
OBJ: Define pH and test the pH of various substances
The pH Scale
 Indicates the concentrations of H+ ions in a solution
 Ranges from 0-14
 7 Neutral
 14 very basic
 0 very acidic
Acids
 Any compound that forms H+ ions in a solution
 Low numbers on the pH scale
 Examples: rain, tomato juice, lemon juice, stomach acid
Bases
 Compound that produces hydroxide ions
 High numbers on the pH scale
 Examples: Milk, Sea water, Soap, Bleach
Humans and pH
 Human fluids must
generally be kept at
6.5-7.5
 Controlling pH is
important for
maintaining
homeostasis
 Medical Example:
Heartburn