CEM 141 Exam 1 Review Questions with
Answers
Constructing a Scientific Explanation - -1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
- Scientific Theory - -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 - -Law: phenomenon; explains WHAT
Theory: tells WHY
- How do we know atoms exist? - -We can see them using atomic force
microscopy (AFM) and scanning tunneling microscopy (STM)
- Atomic Theory Development - -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? - -Different # of protons and atomic symbol
- What types of evidence might be used to conclude tat you had isolated a
new element? - -Would have new properties
- What types of elements would be difficult to identify? - -Ones that aren't
reactive (Ex. Noble gases)
- What is the difference between an atom and a molecule? - -Molecule:
collection of atoms chemically bonded
- What is the difference between an element and a compound? - -An
element is one type of atom vs a compound is several different atoms
connected
- Atom - -is the smallest unit of an element
- Dalton's Atomic Theory - -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 - -The electron was discovered first (it
was the easiest to move and detect) by JJ Thompson
- Discovery of Electron - -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 - -Plum Pudding Model
- Thompson's Experiment showed... - -"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? - -Has 2 protons and 2 neutrons; the nucleus of
a helium atom
- Rutherford's Experiment - -Shot alpha particles through gold foil; some
were deflected and some shot straight through
- In Rutherford's experiment, if the atom was like a plum pudding all the
alpha particles should go straight through... - -But a few of the particles did
not go through, most went straight through, and some went through but
were deflected. This shows of that the atom was mostly empty space with a
small dense nucleus in the center.
- Neutrons (1932) were harder to detect because - -they had no charge and
aren't manipulated with electric and magnetic fields, they reside in the
nucleus, and are slightly heavier than protons
Answers
Constructing a Scientific Explanation - -1. Claim (target of explanation)
2. Evidence (data used to support)
3. Reasoning (connection between claim and evidence)
- Scientific Theory - -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 - -Law: phenomenon; explains WHAT
Theory: tells WHY
- How do we know atoms exist? - -We can see them using atomic force
microscopy (AFM) and scanning tunneling microscopy (STM)
- Atomic Theory Development - -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? - -Different # of protons and atomic symbol
- What types of evidence might be used to conclude tat you had isolated a
new element? - -Would have new properties
- What types of elements would be difficult to identify? - -Ones that aren't
reactive (Ex. Noble gases)
- What is the difference between an atom and a molecule? - -Molecule:
collection of atoms chemically bonded
- What is the difference between an element and a compound? - -An
element is one type of atom vs a compound is several different atoms
connected
- Atom - -is the smallest unit of an element
- Dalton's Atomic Theory - -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 - -The electron was discovered first (it
was the easiest to move and detect) by JJ Thompson
- Discovery of Electron - -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 - -Plum Pudding Model
- Thompson's Experiment showed... - -"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? - -Has 2 protons and 2 neutrons; the nucleus of
a helium atom
- Rutherford's Experiment - -Shot alpha particles through gold foil; some
were deflected and some shot straight through
- In Rutherford's experiment, if the atom was like a plum pudding all the
alpha particles should go straight through... - -But a few of the particles did
not go through, most went straight through, and some went through but
were deflected. This shows of that the atom was mostly empty space with a
small dense nucleus in the center.
- Neutrons (1932) were harder to detect because - -they had no charge and
aren't manipulated with electric and magnetic fields, they reside in the
nucleus, and are slightly heavier than protons
