Transition Work Flashcards
When is a measurement valid?
When it measures what it’s supposed to be measuring
When is a result accurate
When it’s close to the true value
What are precise results
When repeat measurements consistently agree with each other
What is repeatability
How precise measurements are when repeated by the same person, with the same equipment and under the same conditions
What is reproducibility?
How precise measurements are when taken by a 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 is a random error?
An error caused by results varying around the true value in an unpredictable way
What is a systematic error?
A consist difference between the measured values and true values
What does zero error mean?
A measuring instrument takes a false reading when the true value is supposed to be zero
Which variable is changed or selected by the investigator?
Independent variable
What is the dependent variable?
A variable 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 contains protons and neutrons surrounded by electrons on shells
What is the relative mass of protons
1
What is the relative mass of neutrons
1
What is the relative mass of electrons
1/1840 (very small)
What are the relative charges of protons, neutrons and electrons
+1 , 0 , -1
How do the number of protons and electrons differ in an atom
They’re the same as the atoms have a 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?
An atom with the same number of protons but different number of neutrons
What is an ion?
An atom with a charge
What is the function of a mass spectrometer?
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 can contain?
2n^2 (n is the number of the shell)
What are the first four electron sub-shells called?
s, p, d, f (in order)
How many electrons can each orbital hold
maximum of 2
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
What is the unit for ionisation energy
kJmol^-1
What is the equation for relative molecular mass
relative atomic mass = average mass of 1 molecule / (1/12 mass of 1 atom of carbon-12)
What is relative molecular mass
the average mass of one molecule of a substance when when compared with 1/12 of the mass of an atom of carbon-12
What is the equation for relative atomic mass?
Average mass of 1 atom / (1/12th mass of 1 atom of carbon-12)
