Bridge Work Flashcards
When is a measurement valid?
when it measures what it is supposed to be measuring
When is a result accurate
when it is close to the true value
What are precise results
when repeat measurements are consistent/agree closely with
each other
What is repeatability?
how precise repeated measurements are when they are taken
by the same person, using the same equipment, under the
same conditions
What is reproducibility?
how precise repeated measurements are when they are taken
by different people, using different equipment
What is the uncertainty of a measurement?
the interval within which the true value is expected to lie
Define measurement error
the difference between a measured value and the true value
What type of error is caused by results varying
around the true value in an unpredictable way?
Random error
What is a systematic error?
a consistent difference between the measured values and true
values
What does zero error mean?
a measuring instrument gives a false reading when the true
value should be zero
Which variable is changed or selected by the
investigator?
independent variable
What is a dependent variable?
a variable that is measured every time the independent
variable is changed
Define a fair test
a test in which only the independent variable is allowed to
affect the dependent variable
What are control variables?
variables that should be kept constant to avoid them affecting
the dependent variable
What does an atom consist of?
a nucleus containing protons and neutrons, surrounded by
electrons
What are the relative masses of a proton,
neutron, and electron?
1, 1, and 1/1840 respectively
What are the relative charges of a proton,
neutron, and electro
+1, 0, and -1 respectively
How do the number of protons and electrons
differ in an atom
they are the same because atoms have neutral charge
What force holds an atomic nucleus together?
strong nuclear force
What is the atomic number of an element?
the number of protons in the nucleus of a single atom of an
element
What is the mass number of an element?
number of protons + number of neutrons
What is an isotope?
n atom with the same number of protons but different
number of neutrons
What is an ion?
an atom, or group of atoms, with a charge
What is the function of a mass spectrometer?
it accurately determines the mass and abundance of separate
atoms or molecules, to help us identify them
What is a mass spectrum?
the output from a mass spectrometer that shows the different
isotopes that make up an element
What is the total number of electrons that each
electron shell (main energy level) can contain?
2n^2 electrons, where n is the number of the shell
How many electrons can the first three electron
shells hold each?
2 electrons (first shell), 8 electrons (second shell), 18
electrons (third shell)
What are the first four electron sub-shells
(orbitals) called?
s, p, d, and f (in order)
How many electrons can each orbital hold
a maximum of 2 electrons
Define the term ionisation energy, and give its
unit
the energy it takes to remove a mole of electrons from a mole
of atoms in the gaseous state, unit = kJ mol-1
What is the equation for relative atomic mass
(Ar)?
= average mass of 1atom
Over
1 twelfth mass of 1 atom carbon 12
What is the equation for relative molecular mass
(Mr)?
Average mass of 1 molecule
Over
1/12th mass of 1 atom 12C
