CEM 141 EXAM 3 EXAM WITH
CORRECT QUESTIONS AND ANSWERS
2025
Why is nitrogen a gas at room temperature and carbon is a solid? - CORRECT-
ANSWERSthe nitrogen molecules interact with each other through LDFs caused by the
momentary fluctuating dipoles. Carbon atoms form localized, strong interactions
between the atoms (covalent bonds). It would take much more energy to break the
bonds between the carbon atoms than it would to overcome the LDFs between the
nitrogen molecules
Using the evidence provided in the table, explain the pattern that you identified in
question 3. - CORRECT-ANSWERSThe network solids have higher melting and boiling
points because both metallic bonds and covalent bonds are very strong interactions.
These strong interactions must be broken when the solid melts (or the liquid boils). It
would require a lot of energy (high temperature) to break these interactions.
, LDFs are relatively weak interactions. Less energy is required (lower temperatures) to
overcome these interactions. It is the LDFs (not the bonds within the molecules) that are
overcome when the solid melts.
What pattern do you see regarding the melting and boiling points of these elements
relative to the types of bonding and interactions overcome during a phase change? -
CORRECT-ANSWERSElemental forms with very high melting and boiling points are
extended network solids. The atoms are held together by metallic bonding or covalent
bonds.
Elemental forms with lower melting and boiling points are made of either discrete atoms
or small molecules with LDFs between them.
CORRECT QUESTIONS AND ANSWERS
2025
Why is nitrogen a gas at room temperature and carbon is a solid? - CORRECT-
ANSWERSthe nitrogen molecules interact with each other through LDFs caused by the
momentary fluctuating dipoles. Carbon atoms form localized, strong interactions
between the atoms (covalent bonds). It would take much more energy to break the
bonds between the carbon atoms than it would to overcome the LDFs between the
nitrogen molecules
Using the evidence provided in the table, explain the pattern that you identified in
question 3. - CORRECT-ANSWERSThe network solids have higher melting and boiling
points because both metallic bonds and covalent bonds are very strong interactions.
These strong interactions must be broken when the solid melts (or the liquid boils). It
would require a lot of energy (high temperature) to break these interactions.
, LDFs are relatively weak interactions. Less energy is required (lower temperatures) to
overcome these interactions. It is the LDFs (not the bonds within the molecules) that are
overcome when the solid melts.
What pattern do you see regarding the melting and boiling points of these elements
relative to the types of bonding and interactions overcome during a phase change? -
CORRECT-ANSWERSElemental forms with very high melting and boiling points are
extended network solids. The atoms are held together by metallic bonding or covalent
bonds.
Elemental forms with lower melting and boiling points are made of either discrete atoms
or small molecules with LDFs between them.
