CEM 141 MODULE 1 EXAM QUESTIONS
AND ANSWERS
How would you explain the PE of a pencil? - Answer-PE is associated w the system of
the pencil and the earth interacting with the gravitational field.
Here is Katie again, the ball is falling down. As the ball moves towards the ground what
happens to the potential energy of the system (ball + Earth)? - Answer-Decrease
Here is Katie again. The ball is falling down. What causes the potential energy to
decrease? WHY? - Answer-The change in position between the ball and earth in the
gravitational field
What distinguishes one element from another? - Answer-their protons in the nucleus
What types of evidence might be used to conclude that you had isolated a new
element? - Answer-an element composed of atoms w a new number of protons, diff #
protons, unique set of properties
What types of elements would be difficult to identify? - Answer-something nonreactive,
bc they are identifiable based on properties
What is the difference between an element and a compound? - Answer-compounds are
2 or more types of elements which are chemically bonded
elements are a collection of atoms
Dalton's Atomic Theory - Answer-1) Elements are composed of small indivisible,
indestructible particles called atoms.
2) All atoms of an element are identical and have the same mass and properties.
3) Atoms of a given element are different from atoms of other elements.
4) Compounds are formed by combinations of atoms of two or more elements.
5) Chemical reactions are due to the rearrangements of atoms; atoms (matter) are
neither created nor destroyed during a reaction.
How did Dalton Come up w his theory? - Answer-based on reacting different elements
together to form compounds
, How did dalton and the greeks differ? - Answer-greeks believed shape determined
properties
dalton believed composition determined properties
What is still true from Dalton's Atomic Theory? - Answer-Atoms of a given element are
different from atoms of other elements. Y
Compounds are formed by combinations of atoms of two or more elements. Y
Chemical reactions are due to the rearrangements of atoms; atoms (matter) are neither
created nor destroyed during a reaction.Y
JJ Thompson - Answer-discovered the electron
Cathode Ray Tube Experiment - Answer-*glass tube consisted of 2 electrodes under
very low pressure.
*High voltage is applied and the cathode emits particles that move toward anode
*Particle rays bend toward + platte
*mass of particles was about 2000 times lighter than H atom (1st evidence of particle
smaller than an atom)
*type of metal that the cathode was made of did not affect the behavior of the ray, it did
not affect the type of particles (always had same madd to charge ratio
*provided evidence for atoms and substructure of atoms
Thompson's experiment showed - Answer-*Particles emerged from one disc (the
cathode) and moved to the other (the anode)
*these particles could be deflected by electrical fields in a direction that would indicate
they were neg charged
*they carried the electric charge
*the metal that the cathode was made of did not affect the behavior of the ray
*all atoms contain electrons
What is the evidence from Thomson's experiment that all atoms contain electrons?
a)The particles were attracted to the + electrode.
b)The particles were deflected by magnetic fields.
c)The particles were deflected by electrical fields.
d)The particles were identical regardless of the metal used for the cathode (where they
were emitted from). - Answer-d
What was Thomson's model and what does it look like? - Answer-Plum pudding
Atoms contain electrons "embedded" in a positively charged blob. positively charged
body w electrons embedded in it.
What is an alpha particle? - Answer-An alpha particle has 2 protons and 2 neutrons.
It is the nucleus of a helium atom. overall charge 2+
AND ANSWERS
How would you explain the PE of a pencil? - Answer-PE is associated w the system of
the pencil and the earth interacting with the gravitational field.
Here is Katie again, the ball is falling down. As the ball moves towards the ground what
happens to the potential energy of the system (ball + Earth)? - Answer-Decrease
Here is Katie again. The ball is falling down. What causes the potential energy to
decrease? WHY? - Answer-The change in position between the ball and earth in the
gravitational field
What distinguishes one element from another? - Answer-their protons in the nucleus
What types of evidence might be used to conclude that you had isolated a new
element? - Answer-an element composed of atoms w a new number of protons, diff #
protons, unique set of properties
What types of elements would be difficult to identify? - Answer-something nonreactive,
bc they are identifiable based on properties
What is the difference between an element and a compound? - Answer-compounds are
2 or more types of elements which are chemically bonded
elements are a collection of atoms
Dalton's Atomic Theory - Answer-1) Elements are composed of small indivisible,
indestructible particles called atoms.
2) All atoms of an element are identical and have the same mass and properties.
3) Atoms of a given element are different from atoms of other elements.
4) Compounds are formed by combinations of atoms of two or more elements.
5) Chemical reactions are due to the rearrangements of atoms; atoms (matter) are
neither created nor destroyed during a reaction.
How did Dalton Come up w his theory? - Answer-based on reacting different elements
together to form compounds
, How did dalton and the greeks differ? - Answer-greeks believed shape determined
properties
dalton believed composition determined properties
What is still true from Dalton's Atomic Theory? - Answer-Atoms of a given element are
different from atoms of other elements. Y
Compounds are formed by combinations of atoms of two or more elements. Y
Chemical reactions are due to the rearrangements of atoms; atoms (matter) are neither
created nor destroyed during a reaction.Y
JJ Thompson - Answer-discovered the electron
Cathode Ray Tube Experiment - Answer-*glass tube consisted of 2 electrodes under
very low pressure.
*High voltage is applied and the cathode emits particles that move toward anode
*Particle rays bend toward + platte
*mass of particles was about 2000 times lighter than H atom (1st evidence of particle
smaller than an atom)
*type of metal that the cathode was made of did not affect the behavior of the ray, it did
not affect the type of particles (always had same madd to charge ratio
*provided evidence for atoms and substructure of atoms
Thompson's experiment showed - Answer-*Particles emerged from one disc (the
cathode) and moved to the other (the anode)
*these particles could be deflected by electrical fields in a direction that would indicate
they were neg charged
*they carried the electric charge
*the metal that the cathode was made of did not affect the behavior of the ray
*all atoms contain electrons
What is the evidence from Thomson's experiment that all atoms contain electrons?
a)The particles were attracted to the + electrode.
b)The particles were deflected by magnetic fields.
c)The particles were deflected by electrical fields.
d)The particles were identical regardless of the metal used for the cathode (where they
were emitted from). - Answer-d
What was Thomson's model and what does it look like? - Answer-Plum pudding
Atoms contain electrons "embedded" in a positively charged blob. positively charged
body w electrons embedded in it.
What is an alpha particle? - Answer-An alpha particle has 2 protons and 2 neutrons.
It is the nucleus of a helium atom. overall charge 2+
