TX PACT 4-8 CORE (790) QUESTIONS
AND ANSWERS ALREADY PASSED
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.
AND ANSWERS ALREADY PASSED
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.
