CEM 141 EXAM 1 REVIEW QUESTIONS
AND ANSWERS WITH SOLUTIONS 2024
Constructing a Scientific Explanation - ANSWER 1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
Scientific Theory - 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 - ANSWER Law: phenomenon; explains WHAT
Theory: tells WHY
How do we know atoms exist? - ANSWER We can see them using atomic force microscopy (AFM) and
scanning tunneling microscopy (STM)
Atomic Theory Development - 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? - ANSWER
Different # of protons and atomic symbol
What types of evidence might be used to conclude tat you had isolated a new element? - ANSWER
Would have new properties
What types of elements would be difficult to identify? - ANSWER Ones that aren't reactive (Ex. Noble
gases)
What is the difference between an atom and a molecule? - ANSWER Molecule: collection of atoms
chemically bonded
, What is the difference between an element and a compound? - ANSWER An element is one type of atom
vs a compound is several different atoms connected
Atom - ANSWER is the smallest unit of an element
Dalton's Atomic Theory - 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 - ANSWER The electron was discovered first (it was the easiest to
move and detect) by JJ Thompson
Discovery of Electron - 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 - ANSWER Plum Pudding Model
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 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
What is an alpha particle? - ANSWER Has 2 protons and 2 neutrons; the nucleus of a helium atom
AND ANSWERS WITH SOLUTIONS 2024
Constructing a Scientific Explanation - ANSWER 1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
Scientific Theory - 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 - ANSWER Law: phenomenon; explains WHAT
Theory: tells WHY
How do we know atoms exist? - ANSWER We can see them using atomic force microscopy (AFM) and
scanning tunneling microscopy (STM)
Atomic Theory Development - 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? - ANSWER
Different # of protons and atomic symbol
What types of evidence might be used to conclude tat you had isolated a new element? - ANSWER
Would have new properties
What types of elements would be difficult to identify? - ANSWER Ones that aren't reactive (Ex. Noble
gases)
What is the difference between an atom and a molecule? - ANSWER Molecule: collection of atoms
chemically bonded
, What is the difference between an element and a compound? - ANSWER An element is one type of atom
vs a compound is several different atoms connected
Atom - ANSWER is the smallest unit of an element
Dalton's Atomic Theory - 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 - ANSWER The electron was discovered first (it was the easiest to
move and detect) by JJ Thompson
Discovery of Electron - 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 - ANSWER Plum Pudding Model
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 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
What is an alpha particle? - ANSWER Has 2 protons and 2 neutrons; the nucleus of a helium atom
