CEM 141 EXAM 3 QUESTIONS & ANSWERS
Change of state from solid -> liquid -> gas ________ energy - Answer -requires
Energy needed to phase change from solid --> liquid --> gas comes from: - Answer -the
surroundings
When phases change from solid --> liquid --> gas, interactions are _______ between
molecules - Answer -overcome
Change of state from gas --> liquid --> solid ______ energy - Answer -releases
What happens to the energy from a phase change from gas --> liquid --> solid? -
Answer -released to surroundings
When phases change from gas --> liquid --> solid, interactions are _______ between
molecules - Answer -formed
What happens when a substance melts? - Answer -the interactions between the
particles have to be overcome -- so that they can remove relative to each other (that's
what allows a liquid to flow)
Melting and boiling points provide an estimate of: - Answer -the strength of the
attractive interactions between particles
Which is stronger?? Covalent bond/LDF - Answer -covalent bond
In a covalent bond, what is formed? - Answer -a new molecule
What is a LDF caused by? - Answer -fluctuating charge distribution
Covalent bonds are the sharing of: - Answer -valence electrons
LDF's increase with.... - Answer -the size of electron cloud
Covalent bonds are caused by: - Answer -attraction between electrons of one atom and
the nucleus of another
Ldfs are present where??? - Answer -between all molecular species
Is it hard or easy to predict covalent bond strength? - Answer -hard
When are covalent bonds present? - Answer -when atomic orbitals interact
constructively
, Covalent bonds are located: - Answer -between molecules/networks
Ldfs occur between: - Answer -separate molecules
Diamond has a high/low melting point??? - Answer -high
Graphite has a high/low melting point?? - Answer -high
Diamond is hard/soft? - Answer -hard
Graphite is hard/soft? - Answer -soft
Diamond's physical properties - Answer -brittle, translucent
Diamond does/does not conduct electricity?? - Answer -does not
Graphite's physical properties - Answer -slippery, shiny, grey
Graphite does/does not conduct electricity? - Answer -does
In diamond, each carbon forms how many bonds to how many carbons??? - Answer -4
bonds to 4 identical carbons
In diamond, the bonds between carbons arrange themselves towards: - Answer -the
corners of a 4-sided figure (tetrahedron)
What is the C-C-C bond angle in diamond? - Answer -109°
What model of bonding is used to explain the bonding in carbon? - Answer -Valence
Bond Theory
Valence Bond Theory - Answer -atomic orbitals overlap to form bonds
How are bonds often shown in the valence bond theory? - Answer -as "sticks"
In the Molecular Orbital Theory, atomic orbitals combine to form: - Answer -an equal #
of molecular orbitals
In MO Theory, each orbital can contain up to ____ electrons - Answer -2
In MO theory, electrons in bonding orbitals (stabilized/destabilized) the system?? -
Answer -stabilized
In MO theory, each bond is made up of how many electrons? - Answer -2 electrons
Change of state from solid -> liquid -> gas ________ energy - Answer -requires
Energy needed to phase change from solid --> liquid --> gas comes from: - Answer -the
surroundings
When phases change from solid --> liquid --> gas, interactions are _______ between
molecules - Answer -overcome
Change of state from gas --> liquid --> solid ______ energy - Answer -releases
What happens to the energy from a phase change from gas --> liquid --> solid? -
Answer -released to surroundings
When phases change from gas --> liquid --> solid, interactions are _______ between
molecules - Answer -formed
What happens when a substance melts? - Answer -the interactions between the
particles have to be overcome -- so that they can remove relative to each other (that's
what allows a liquid to flow)
Melting and boiling points provide an estimate of: - Answer -the strength of the
attractive interactions between particles
Which is stronger?? Covalent bond/LDF - Answer -covalent bond
In a covalent bond, what is formed? - Answer -a new molecule
What is a LDF caused by? - Answer -fluctuating charge distribution
Covalent bonds are the sharing of: - Answer -valence electrons
LDF's increase with.... - Answer -the size of electron cloud
Covalent bonds are caused by: - Answer -attraction between electrons of one atom and
the nucleus of another
Ldfs are present where??? - Answer -between all molecular species
Is it hard or easy to predict covalent bond strength? - Answer -hard
When are covalent bonds present? - Answer -when atomic orbitals interact
constructively
, Covalent bonds are located: - Answer -between molecules/networks
Ldfs occur between: - Answer -separate molecules
Diamond has a high/low melting point??? - Answer -high
Graphite has a high/low melting point?? - Answer -high
Diamond is hard/soft? - Answer -hard
Graphite is hard/soft? - Answer -soft
Diamond's physical properties - Answer -brittle, translucent
Diamond does/does not conduct electricity?? - Answer -does not
Graphite's physical properties - Answer -slippery, shiny, grey
Graphite does/does not conduct electricity? - Answer -does
In diamond, each carbon forms how many bonds to how many carbons??? - Answer -4
bonds to 4 identical carbons
In diamond, the bonds between carbons arrange themselves towards: - Answer -the
corners of a 4-sided figure (tetrahedron)
What is the C-C-C bond angle in diamond? - Answer -109°
What model of bonding is used to explain the bonding in carbon? - Answer -Valence
Bond Theory
Valence Bond Theory - Answer -atomic orbitals overlap to form bonds
How are bonds often shown in the valence bond theory? - Answer -as "sticks"
In the Molecular Orbital Theory, atomic orbitals combine to form: - Answer -an equal #
of molecular orbitals
In MO Theory, each orbital can contain up to ____ electrons - Answer -2
In MO theory, electrons in bonding orbitals (stabilized/destabilized) the system?? -
Answer -stabilized
In MO theory, each bond is made up of how many electrons? - Answer -2 electrons
