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CEM 141 Final Questions with Answers
(100% Correct Answers)
Thomson's experiment allowed him to make the claim that all atoms have a
sub structure and contain smaller particles (electrons) embedded in the
structure of the atom. What evidence and reasoning allowed him to make this
claim? Answer: Evidence: i. Electrons were ejected from the cathode,
regardless of what metal the cathode was made of.
Reasoning: iii. Since the particles are emitted regardless of the nature of the
cathode, they must be part of the sub-structure of the atom.
Which of these statements are true:
i. All neutral atoms and molecules attract eachother.
ii. London Dispersion Forces increase as the size of the electron cloud
increases.
iii. It takes energy to overcome the attractions between particles.
iv. Energy is released to the surroundings when atoms form a stable interaction.
Answer: ALL ARE TRUE
The atomic theory of matter is an example of a scientific theory. What
distinguishes it from a scientific law such as the law of gravity? Answer: The
atomic theory explains the underlying cause of a range of phenomena.
Best set of claim, evidence, and reasoning that can be used to explain the results
of Rutherford's experiments. Answer: CLAIM: The atom is mostly empty
space with a very small dense nucleus.
EVIDENCE: Most alpha particles went straight through, only a few were
deflected.
,2
REASONING: The positively charged alpha particles were deflected by the
repulsive interaction with the positive nucleus; since only a few were deflected
the nucleus must take up a very small volume of the atom.
Which is smallest? An atom, a cell, a proton, or an electron. Answer: An
electron
The distance between the two helium atoms where the system would be the
most stable is... Answer: where the potential energy is at a minimum.
Two atoms approach and get close enough so that their electron clouds
overlap. Why does the potential energy increase? Answer: The electron clouds
repel eachother.
What is the cause of the attractive force between two He atoms? Answer: The
electron clouds of the He atoms may fluctuate randomly causing a transient
dipole that induces a dipole in other atoms which causes them to attract to each
other.
As two positively charged objects approach each other, what happens to the
potential energy of a system? Answer: INCREASES
Is this statement (one of Dalton's atomic theory tenets) true or false and why?
"Elements are composed of small indivisible, indestructible particles called
atoms." Answer: FALSE
Atoms have a sub-structure
If you put bromine liquid in a pan on the stove and heat it up the bromine will
boil. What is the mechanism (process) by which this happens? Answer: As
more bromine molecules get more energy, they can overcome the electrostatic
forces of attraction and the bromine molecules can escape into the gas phase.
In an isolated system, when two atoms collide, which is always true?
-The atom with more KE will transfer energy to the atom with less KE
, 3
-The atom with less KE will transfer energy to the atom with more KE
- The total energy of the system will not change
- The potential energy will decrease Answer: The total energy of the system will
not change
The boiling point of neon is -246 degrees C and the melting point of neon is -
249 degrees C. What state is neon at -260 degrees C? Answer: Solid
What is wrong with the following statement?
"As the ball falls its potential energy decreases" Answer: -A single object cannot
possess PE
-There is no mention of a field
Difference between covalent bonds and LDF's Answer: -Covalent bonds are
interactions within molecules
-LDFs are interactions between separate molecules
In Rutherford's gold foil experiment, the majority of the alpha particles went
straight through the gold. Why was this? Answer: The atom is mostly empty
space, so nothing manipulated the path of the alpha particles.
Thomson's cathode ray tube experiment showed that the beam of emitted
particles was deflected by charged plates. Thomson used this evidence to
support his claim that... Answer: Electrons carried the electrical charge
What is this statement (law or theory) and why?
"Opposite charges are attracted to each other in proportion to the product of
their charges and inversely proportional to the square of the distance between
them." Answer: Scientific Law - it describes the phenomenon
Consider the question: "Will adding fertilizer make my plant grow faster?"
CEM 141 Final Questions with Answers
(100% Correct Answers)
Thomson's experiment allowed him to make the claim that all atoms have a
sub structure and contain smaller particles (electrons) embedded in the
structure of the atom. What evidence and reasoning allowed him to make this
claim? Answer: Evidence: i. Electrons were ejected from the cathode,
regardless of what metal the cathode was made of.
Reasoning: iii. Since the particles are emitted regardless of the nature of the
cathode, they must be part of the sub-structure of the atom.
Which of these statements are true:
i. All neutral atoms and molecules attract eachother.
ii. London Dispersion Forces increase as the size of the electron cloud
increases.
iii. It takes energy to overcome the attractions between particles.
iv. Energy is released to the surroundings when atoms form a stable interaction.
Answer: ALL ARE TRUE
The atomic theory of matter is an example of a scientific theory. What
distinguishes it from a scientific law such as the law of gravity? Answer: The
atomic theory explains the underlying cause of a range of phenomena.
Best set of claim, evidence, and reasoning that can be used to explain the results
of Rutherford's experiments. Answer: CLAIM: The atom is mostly empty
space with a very small dense nucleus.
EVIDENCE: Most alpha particles went straight through, only a few were
deflected.
,2
REASONING: The positively charged alpha particles were deflected by the
repulsive interaction with the positive nucleus; since only a few were deflected
the nucleus must take up a very small volume of the atom.
Which is smallest? An atom, a cell, a proton, or an electron. Answer: An
electron
The distance between the two helium atoms where the system would be the
most stable is... Answer: where the potential energy is at a minimum.
Two atoms approach and get close enough so that their electron clouds
overlap. Why does the potential energy increase? Answer: The electron clouds
repel eachother.
What is the cause of the attractive force between two He atoms? Answer: The
electron clouds of the He atoms may fluctuate randomly causing a transient
dipole that induces a dipole in other atoms which causes them to attract to each
other.
As two positively charged objects approach each other, what happens to the
potential energy of a system? Answer: INCREASES
Is this statement (one of Dalton's atomic theory tenets) true or false and why?
"Elements are composed of small indivisible, indestructible particles called
atoms." Answer: FALSE
Atoms have a sub-structure
If you put bromine liquid in a pan on the stove and heat it up the bromine will
boil. What is the mechanism (process) by which this happens? Answer: As
more bromine molecules get more energy, they can overcome the electrostatic
forces of attraction and the bromine molecules can escape into the gas phase.
In an isolated system, when two atoms collide, which is always true?
-The atom with more KE will transfer energy to the atom with less KE
, 3
-The atom with less KE will transfer energy to the atom with more KE
- The total energy of the system will not change
- The potential energy will decrease Answer: The total energy of the system will
not change
The boiling point of neon is -246 degrees C and the melting point of neon is -
249 degrees C. What state is neon at -260 degrees C? Answer: Solid
What is wrong with the following statement?
"As the ball falls its potential energy decreases" Answer: -A single object cannot
possess PE
-There is no mention of a field
Difference between covalent bonds and LDF's Answer: -Covalent bonds are
interactions within molecules
-LDFs are interactions between separate molecules
In Rutherford's gold foil experiment, the majority of the alpha particles went
straight through the gold. Why was this? Answer: The atom is mostly empty
space, so nothing manipulated the path of the alpha particles.
Thomson's cathode ray tube experiment showed that the beam of emitted
particles was deflected by charged plates. Thomson used this evidence to
support his claim that... Answer: Electrons carried the electrical charge
What is this statement (law or theory) and why?
"Opposite charges are attracted to each other in proportion to the product of
their charges and inversely proportional to the square of the distance between
them." Answer: Scientific Law - it describes the phenomenon
Consider the question: "Will adding fertilizer make my plant grow faster?"
