CEM 141 Exam Latest Updated Questions with 100%
Complete Solutions
Why are alpha particles deflected by the nucleus of the atom?
Because both the alpha particle and the nucleus are positively charged and so the alpha particle is
repelled.
True/False: All atoms of an element are identical and have the same mass and properties.
False
Reasoning for the statement "All atoms of an element are identical and have the same mass
and properties." being true/false.
False; Atoms of the same element can have different numbers of neutrons.
What is the evidence that electrons are subatomic particles?
The nature of the electron is independent of the material form which it emerges.
Which is a theory?
The properties of matter can be explained by understanding that matter is composed of atoms
that interact and move in various predictable ways.
Why is the boiling point of iodine higher than that of bromine?
Because iodine has a larger more polarizable electron cloud.
Reasoning for iodine having a higher boiling point than bromine?
The electrostatic attraction between the iodine molecules requires more energy to overcome.
, This picture is a representation of solid bromine, Br2 (s), which exists as diatomic
molecules. When Br(s) is heated it melts (at 266K) and then becomes a gas (at 332K). What
is happening?
When the bromine melts, attractive forces between molecules are overcome; when the bromine
forms a gas, attractive forces between molecules are overcome.
When liquid oxygen (O2) is cooled down, eventually it freezes. Which of these best explains
the forces and energy changes that take place during this process?
New LDFs are formed, Energy is released to the surroundings, and energy is transferred via
collisions.
For a pencil sitting on a desk, what forces are acting on the pencil?
Both gravitational and electrostatic.
At very low temperatures, at which point in this curve would a system composed of two
helium atoms be most stable?
The well, because the attractive and repulsive forces on the system are equal.
The graph shows the change in potential energy as two particles approach. Which particles
are most likely to produce this change in energy?
Two protons.
How do atoms know that the temperature is increasing?
Thermal energy is transferred upon collision with other atoms.
Complete Solutions
Why are alpha particles deflected by the nucleus of the atom?
Because both the alpha particle and the nucleus are positively charged and so the alpha particle is
repelled.
True/False: All atoms of an element are identical and have the same mass and properties.
False
Reasoning for the statement "All atoms of an element are identical and have the same mass
and properties." being true/false.
False; Atoms of the same element can have different numbers of neutrons.
What is the evidence that electrons are subatomic particles?
The nature of the electron is independent of the material form which it emerges.
Which is a theory?
The properties of matter can be explained by understanding that matter is composed of atoms
that interact and move in various predictable ways.
Why is the boiling point of iodine higher than that of bromine?
Because iodine has a larger more polarizable electron cloud.
Reasoning for iodine having a higher boiling point than bromine?
The electrostatic attraction between the iodine molecules requires more energy to overcome.
, This picture is a representation of solid bromine, Br2 (s), which exists as diatomic
molecules. When Br(s) is heated it melts (at 266K) and then becomes a gas (at 332K). What
is happening?
When the bromine melts, attractive forces between molecules are overcome; when the bromine
forms a gas, attractive forces between molecules are overcome.
When liquid oxygen (O2) is cooled down, eventually it freezes. Which of these best explains
the forces and energy changes that take place during this process?
New LDFs are formed, Energy is released to the surroundings, and energy is transferred via
collisions.
For a pencil sitting on a desk, what forces are acting on the pencil?
Both gravitational and electrostatic.
At very low temperatures, at which point in this curve would a system composed of two
helium atoms be most stable?
The well, because the attractive and repulsive forces on the system are equal.
The graph shows the change in potential energy as two particles approach. Which particles
are most likely to produce this change in energy?
Two protons.
How do atoms know that the temperature is increasing?
Thermal energy is transferred upon collision with other atoms.
