CEM 141 Exam 1 Review UPDATED
ACTUAL QUESTIONS AND CORRECT
ANSWERS
Constructing a Scientific Explanation - CORRECT ANSWER 1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
Scientific Theory - CORRECT ANSWER explains how/why; best available explanation of
existing evidence; makes testable predictions; is falsifiable; may change over time with new evidence
Difference Between Law and Theory - CORRECT ANSWER Law: phenomenon; explains
WHAT
Theory: tells WHY
How do we know atoms exist? - CORRECT ANSWER We can see them using atomic force
microscopy (AFM) and scanning tunneling microscopy (STM)
Atomic Theory Development - CORRECT ANSWER The original idea came from the Greeks;
wasn't a scientific theory but philosophy (Ex. Elements=earth, fire, air, water and were thought to be
in constant motion based on watching the movement of specks of dust in sunlight and that there was
nothing between them AKA Brownian Motion)
What distinguishes one element from another? How do atoms of different elements differ? -
CORRECT ANSWER Different # of protons and atomic symbol
What types of evidence might be used to conclude tat you had isolated a new element? - CORRECT
ANSWER Would have new properties
What types of elements would be difficult to identify? - CORRECT ANSWER Ones that aren't
reactive (Ex. Noble gases)
, What is the difference between an atom and a molecule? - CORRECT ANSWER Molecule:
collection of atoms chemically bonded
What is the difference between an element and a compound? - CORRECT ANSWER An
element is one type of atom vs a compound is several different atoms connected
Atom - CORRECT ANSWER is the smallest unit of an element
Dalton's Atomic Theory - CORRECT ANSWER 1. Elements are composed of small
indivisible, indestructible particles called atoms (NOT TRUE)
2. All atoms of an element are identical and have the same mass and properties (NOT TRUE)
3. Atoms of a given element are different from atoms of other elements. (TRUE)
4. Compounds are formed by combinations of atoms of 2 or more elements (TRUE)
5. Chemical reactions are due to the rearrangement of atoms, atoms (matter) are neither created nor
destroyed during a reaction (TRUE)
Atoms have a subatomic structure - CORRECT ANSWER The electron was discovered first (it
was the easiest to move and detect) by JJ Thompson
Discovery of Electron - CORRECT ANSWER Cathode ray tube: glass tube consisting of 2
electrodes under very low pressure. When a high voltage is applied, cathode emits "particles" that
move toward anode. Particle rays bend toward positive plate. Therefore they're negatively charged
particles.
Thompson's Atomic Model - CORRECT ANSWER Plum Pudding Model
Thompson's Experiment showed... - CORRECT 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 negatively charged; the particles could also be deflected
by magnetic fields; the particles carried the electrical charge—that is if the ray was bent, for example
by a magnetic field, the charge went with it; the metal that the cathode was made of didn't affect the
behavior of the ray—so whatever the composition of the ray—it appeared to be independent of the
element that it came from
ACTUAL QUESTIONS AND CORRECT
ANSWERS
Constructing a Scientific Explanation - CORRECT ANSWER 1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
Scientific Theory - CORRECT ANSWER explains how/why; best available explanation of
existing evidence; makes testable predictions; is falsifiable; may change over time with new evidence
Difference Between Law and Theory - CORRECT ANSWER Law: phenomenon; explains
WHAT
Theory: tells WHY
How do we know atoms exist? - CORRECT ANSWER We can see them using atomic force
microscopy (AFM) and scanning tunneling microscopy (STM)
Atomic Theory Development - CORRECT ANSWER The original idea came from the Greeks;
wasn't a scientific theory but philosophy (Ex. Elements=earth, fire, air, water and were thought to be
in constant motion based on watching the movement of specks of dust in sunlight and that there was
nothing between them AKA Brownian Motion)
What distinguishes one element from another? How do atoms of different elements differ? -
CORRECT ANSWER Different # of protons and atomic symbol
What types of evidence might be used to conclude tat you had isolated a new element? - CORRECT
ANSWER Would have new properties
What types of elements would be difficult to identify? - CORRECT ANSWER Ones that aren't
reactive (Ex. Noble gases)
, What is the difference between an atom and a molecule? - CORRECT ANSWER Molecule:
collection of atoms chemically bonded
What is the difference between an element and a compound? - CORRECT ANSWER An
element is one type of atom vs a compound is several different atoms connected
Atom - CORRECT ANSWER is the smallest unit of an element
Dalton's Atomic Theory - CORRECT ANSWER 1. Elements are composed of small
indivisible, indestructible particles called atoms (NOT TRUE)
2. All atoms of an element are identical and have the same mass and properties (NOT TRUE)
3. Atoms of a given element are different from atoms of other elements. (TRUE)
4. Compounds are formed by combinations of atoms of 2 or more elements (TRUE)
5. Chemical reactions are due to the rearrangement of atoms, atoms (matter) are neither created nor
destroyed during a reaction (TRUE)
Atoms have a subatomic structure - CORRECT ANSWER The electron was discovered first (it
was the easiest to move and detect) by JJ Thompson
Discovery of Electron - CORRECT ANSWER Cathode ray tube: glass tube consisting of 2
electrodes under very low pressure. When a high voltage is applied, cathode emits "particles" that
move toward anode. Particle rays bend toward positive plate. Therefore they're negatively charged
particles.
Thompson's Atomic Model - CORRECT ANSWER Plum Pudding Model
Thompson's Experiment showed... - CORRECT 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 negatively charged; the particles could also be deflected
by magnetic fields; the particles carried the electrical charge—that is if the ray was bent, for example
by a magnetic field, the charge went with it; the metal that the cathode was made of didn't affect the
behavior of the ray—so whatever the composition of the ray—it appeared to be independent of the
element that it came from
