CEM 141
CEM 141 Exam 1 Review with Correct
Answers Graded A+ 2026
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)
CEM 141
, CEM 141
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
CEM 141
CEM 141 Exam 1 Review with Correct
Answers Graded A+ 2026
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)
CEM 141
, CEM 141
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
CEM 141
