TX PACT 4-8 CORE (790) Exam with complete solution
How many SFs in 0.010025600?
8
SFs: Addition and Subtraction Rules
answer has the same # decimal places as numeral w/the smallest # of decimal places.
EX: 1063.02 + 12.5 = 1075.5
SFs: Multiplication/Division Rules
answer has the same # of SFs as numeral with smallest # of SFs.
EX: 1063.02 x 12.5 = 13287.75 => 1.33 x 10^4
Define: Hypothesis, Theory, and Scientific Law
Hypothesis: testable prediction based on observations (educated guess)
Theory: proposed explanation, based on evidence, that may or may not be testable.
(educated explanation on why something happens)
Scientific Law: proven and documented description of observations surrounding
phenomena (states what will happen not why)
*theories do not become laws
independent variable
The experimental factor that is manipulated by the scientist; the variable whose effect is
being studied. (usually on x-axis)
dependent variable
The measurable factor; the variable that may change in response to (or depend on)
manipulations of the independent variable.
Precision
a measure of how close a series of measurements are to one another
Accuracy
how close a measurement is to the true value
Negative feedback
A type of regulation that responds to a change in conditions by initiating responses that
will counteract the change or correct the system back to original state. Maintains a
steady state (homeostasis).
EX: body temperature
Positive feedback
A type of regulation that responds to a change in conditions by initiating responses that
will amplify the change. Takes organism away from a steady state.
EX: Global warming or contractions
Matter
Anything that has mass and takes up space (made up of atoms)
Ground state of atoms
lowest energy, most stable electron configuration
Neutrons
neutral charge; mass # - atomic # (protons)
Quantum Model
current atomic model in which e- move in waves around nucleus (w/ uncertain positions
in an e- cloud)
,Molecules vs. Compounds
Molecules: Groups of two or more atoms held together by chemical bonds
Ex: O2 & consist of compounds too
Compounds: 2 or more DIFF. elements held by ionic or molecular bonds
Ex: H2O, NaCl, etc..
Isotopes
atoms w/ same # of protons, but diff. # of neutrons
Radioactivity
The spontaneous nuclear emission of radiation by an unstable atomic nucleus, which
changes # of protons (identity of element)
Alpha Decay
Radioactive decay in which an atom emits an alpha particle (w/ 2P and 2N). This
decreases the atomic # by 2 and the mass number by 4.
emission of helium-4 nucleus
Beta Decay
radioactive decay in which neutron changes into proton by emitting an e- and neutrino.
This increases atomic # by 1 and mass stays the same.
emission of an electron or a positron
Gamma Decay
radioactive decay by emission of a gamma ray; atomic # and mass # do not change.
carbon dating
uses half life to approximate age of fossils.
solute
the substance that is dissolved in solvent
"pUT the solUTe in the solvent"
density
mass/volume
Kinetic Molecular Theory of Matter
all matter is constantly in motion
- KE and speed increases as temp. increases
Wind turbine energy transformation
kinetic (wind moves motor) to mechanical (generator)
strongest to weakest bonds
covalent, ionic, hydrogen
types of bonds
- covalent: e- are shared b/t 2 atoms (usually NM)
- ionic: oppositely charged ion attraction - one atom loses e-, other accepts [one M (+),
one NM (-)]
, - metallic: 2 metal atoms
- hydrogen: weak bonds, easily breakable
states of matter
solid: rigid, fixed shape & volume
liquid: fixed volume
gas: compressible
during a phase change, temp. is constant until change is complete and matter is
conserved
Combination Rxn
A+B-->AB
Decomposition Rxn
AB --> A + B
Single Replacement Rxn
One element/molecule replaces another
A + BC --> B + AC
Double Replacement Rxn
AB + CD --> AD + CB
Combustion Rxn
C reacts with O2, burns, and produces CO2 and H2O in the process.
Redox Rxn
transfer of electrons that changes charge (oxidation #) of atom in the reaction
Oxidation
OIL = losing e-
0 --> 1+ b/c lost an e- to make + charge
Reduction
RIG = gaining e-
1+ --> 0 b/c gained an e- to make neutral charge
Energy
ability to create heat or do work; always conserved
Thermal Energy
The total internal energy of all of the particles motion in a substance -- transfers heat
Heat Energy
transfer of thermal energy - energy transferred from hot to cold
Laws of Thermodynamics
- Zeroth: 2 bodies are in thermal equil. w/ 3rd body, then they are all in thermal equil.
(have the same temp.)
- 1st: Internal Energy (U) = Heat (Q) - Work
Work done by system = +W
Work done on system = -W
How many SFs in 0.010025600?
8
SFs: Addition and Subtraction Rules
answer has the same # decimal places as numeral w/the smallest # of decimal places.
EX: 1063.02 + 12.5 = 1075.5
SFs: Multiplication/Division Rules
answer has the same # of SFs as numeral with smallest # of SFs.
EX: 1063.02 x 12.5 = 13287.75 => 1.33 x 10^4
Define: Hypothesis, Theory, and Scientific Law
Hypothesis: testable prediction based on observations (educated guess)
Theory: proposed explanation, based on evidence, that may or may not be testable.
(educated explanation on why something happens)
Scientific Law: proven and documented description of observations surrounding
phenomena (states what will happen not why)
*theories do not become laws
independent variable
The experimental factor that is manipulated by the scientist; the variable whose effect is
being studied. (usually on x-axis)
dependent variable
The measurable factor; the variable that may change in response to (or depend on)
manipulations of the independent variable.
Precision
a measure of how close a series of measurements are to one another
Accuracy
how close a measurement is to the true value
Negative feedback
A type of regulation that responds to a change in conditions by initiating responses that
will counteract the change or correct the system back to original state. Maintains a
steady state (homeostasis).
EX: body temperature
Positive feedback
A type of regulation that responds to a change in conditions by initiating responses that
will amplify the change. Takes organism away from a steady state.
EX: Global warming or contractions
Matter
Anything that has mass and takes up space (made up of atoms)
Ground state of atoms
lowest energy, most stable electron configuration
Neutrons
neutral charge; mass # - atomic # (protons)
Quantum Model
current atomic model in which e- move in waves around nucleus (w/ uncertain positions
in an e- cloud)
,Molecules vs. Compounds
Molecules: Groups of two or more atoms held together by chemical bonds
Ex: O2 & consist of compounds too
Compounds: 2 or more DIFF. elements held by ionic or molecular bonds
Ex: H2O, NaCl, etc..
Isotopes
atoms w/ same # of protons, but diff. # of neutrons
Radioactivity
The spontaneous nuclear emission of radiation by an unstable atomic nucleus, which
changes # of protons (identity of element)
Alpha Decay
Radioactive decay in which an atom emits an alpha particle (w/ 2P and 2N). This
decreases the atomic # by 2 and the mass number by 4.
emission of helium-4 nucleus
Beta Decay
radioactive decay in which neutron changes into proton by emitting an e- and neutrino.
This increases atomic # by 1 and mass stays the same.
emission of an electron or a positron
Gamma Decay
radioactive decay by emission of a gamma ray; atomic # and mass # do not change.
carbon dating
uses half life to approximate age of fossils.
solute
the substance that is dissolved in solvent
"pUT the solUTe in the solvent"
density
mass/volume
Kinetic Molecular Theory of Matter
all matter is constantly in motion
- KE and speed increases as temp. increases
Wind turbine energy transformation
kinetic (wind moves motor) to mechanical (generator)
strongest to weakest bonds
covalent, ionic, hydrogen
types of bonds
- covalent: e- are shared b/t 2 atoms (usually NM)
- ionic: oppositely charged ion attraction - one atom loses e-, other accepts [one M (+),
one NM (-)]
, - metallic: 2 metal atoms
- hydrogen: weak bonds, easily breakable
states of matter
solid: rigid, fixed shape & volume
liquid: fixed volume
gas: compressible
during a phase change, temp. is constant until change is complete and matter is
conserved
Combination Rxn
A+B-->AB
Decomposition Rxn
AB --> A + B
Single Replacement Rxn
One element/molecule replaces another
A + BC --> B + AC
Double Replacement Rxn
AB + CD --> AD + CB
Combustion Rxn
C reacts with O2, burns, and produces CO2 and H2O in the process.
Redox Rxn
transfer of electrons that changes charge (oxidation #) of atom in the reaction
Oxidation
OIL = losing e-
0 --> 1+ b/c lost an e- to make + charge
Reduction
RIG = gaining e-
1+ --> 0 b/c gained an e- to make neutral charge
Energy
ability to create heat or do work; always conserved
Thermal Energy
The total internal energy of all of the particles motion in a substance -- transfers heat
Heat Energy
transfer of thermal energy - energy transferred from hot to cold
Laws of Thermodynamics
- Zeroth: 2 bodies are in thermal equil. w/ 3rd body, then they are all in thermal equil.
(have the same temp.)
- 1st: Internal Energy (U) = Heat (Q) - Work
Work done by system = +W
Work done on system = -W
