CEM 141 EXAM 1 QUESTIONS WITH
100% CORRECT ANSWERS
Contrast the energy change that occurs when two helium atoms or two hydrogen atoms
combine - Answer-The energy change will be smaller when two helium atoms are
attracted to each other because LDFs are weaker than covalent bonds, meaning that
more energy will be needed to break the covalent bonds.
Differentiate between LDFs and covalent bonding without providing an explanation -
Answer-LDFs: weaker covalent bonds: stronger
Draw a molecular level picture showing how atoms rearrange during a chemical
reaction - Answer-be able to draw balanced equations with different atoms/molecules
Develop a scientific question, a scientific explanation, and use evidence and data to
make an argument - Answer-be able to do this efficiently
Compare and contrast gravitational and electrostatic forces - Answer-Gravitational and
electrostatic forces require a field and two or more objects. Electromagnetic forces are
much stronger than gravity and are both attractive and repulsive. Gravitational forces
occur between objects that have mass and electrostatic forces occur between objects
with a charge.
Construct an atomic level explanation for why two isolated atoms would attract each
other, and why they would repel if they got too close together - Answer-Due to the
shifting electron clouds, some atoms are more positive on one side and more negative
on the other, also known as a partial charge. This causes another atom to have an
instantaneous dimple, which causes the two atoms to attract because of the attractive
electrostatic force. These atoms attract until the electron clouds overlap. This causes
two of the same charge to be too close together, causing them to repel each other.
Predict and explain the KE, PE, and TE as two isolated helium (or other noble gas)
atoms approach each other - Answer-TE stays the same because it is an isolated
system; PE decreases then increases because the atoms originally move with the force,
but then move against the force, causing an increase in PE. KE increases because
atoms are moving quickly together then decreases when the electron clouds overlap.
What are the diatomic molecules? - Answer-H2, N2, O2, F2, Cl2, Br2, I2
100% CORRECT ANSWERS
Contrast the energy change that occurs when two helium atoms or two hydrogen atoms
combine - Answer-The energy change will be smaller when two helium atoms are
attracted to each other because LDFs are weaker than covalent bonds, meaning that
more energy will be needed to break the covalent bonds.
Differentiate between LDFs and covalent bonding without providing an explanation -
Answer-LDFs: weaker covalent bonds: stronger
Draw a molecular level picture showing how atoms rearrange during a chemical
reaction - Answer-be able to draw balanced equations with different atoms/molecules
Develop a scientific question, a scientific explanation, and use evidence and data to
make an argument - Answer-be able to do this efficiently
Compare and contrast gravitational and electrostatic forces - Answer-Gravitational and
electrostatic forces require a field and two or more objects. Electromagnetic forces are
much stronger than gravity and are both attractive and repulsive. Gravitational forces
occur between objects that have mass and electrostatic forces occur between objects
with a charge.
Construct an atomic level explanation for why two isolated atoms would attract each
other, and why they would repel if they got too close together - Answer-Due to the
shifting electron clouds, some atoms are more positive on one side and more negative
on the other, also known as a partial charge. This causes another atom to have an
instantaneous dimple, which causes the two atoms to attract because of the attractive
electrostatic force. These atoms attract until the electron clouds overlap. This causes
two of the same charge to be too close together, causing them to repel each other.
Predict and explain the KE, PE, and TE as two isolated helium (or other noble gas)
atoms approach each other - Answer-TE stays the same because it is an isolated
system; PE decreases then increases because the atoms originally move with the force,
but then move against the force, causing an increase in PE. KE increases because
atoms are moving quickly together then decreases when the electron clouds overlap.
What are the diatomic molecules? - Answer-H2, N2, O2, F2, Cl2, Br2, I2
