RETRIEVAL QUESTIONS

Question 1

When is a measurement valid?

Answer 1

when it measures what it is supposed to be measuring

Question 2

When is a result accurate?

Answer 2

when it is close to the true value

Question 3

What are precise results?

Answer 3

when repeat measurements are consistent/agree closely with each other

Question 4

What is repeatability?

Answer 4

how precise repeated measurements are when they are taken by the same person, using the same equipment, under the same conditions

Question 5

What is reproducibility?

Answer 5

how precise repeated measurements are when they are taken by different people, using different equipment

Question 6

What is the uncertainty of a measurement?

Answer 6

the interval within which the true value is expected to lie

Question 7

Define measurement error

Answer 7

the difference between a measured value and the true value

Question 8

What type of error is caused by results varying

around the true value in an unpredictable way?

Answer 8

random error

Question 9

What is a systematic error?

Answer 9

a consistent difference between the measured values and true values

Question 10

What does zero error mean?

Answer 10

a measuring instrument gives a false reading when the true value should be zero

Question 11

Which variable is changed or selected by the

investigator?

Answer 11

independent variable

Question 12

What is a dependent variable?

Answer 12

a variable that is measured every time the independent

variable is changed

Question 13

Define a fair test

Answer 13

a test in which only the independent variable is allowed to affect the dependent variable

Question 14

What are control variables?

Answer 14

variables that should be kept constant to avoid them affecting the dependent variable

Question 15

What are the relative masses of a proton,

neutron, and electron?

Answer 15

1, 1, and 1/1840 respectively

Question 16

What force holds an atomic nucleus together?

Answer 16

strong nuclear force

Question 17

Atomic number, Mass number, Ion and Isotope definitions

Answer 17

Ar - #Protons
Mr - #Protons + Electrons
Ion - An atom with a charge
Isotope - Atoms with the same number of protons but a different number of neutrons

Question 18

What is the function of a mass spectrometer?

Answer 18

it accurately determines the mass and abundance of separate atoms or molecules, to help us identify them

Question 19

What is a mass spectrum?

Answer 19

the output from a mass spectrometer that shows the different isotopes that make up an element

Question 20

What is the total number of electrons that each
electron shell (main energy level) can contain?

Answer 20

2n^2 electrons, where n is the number of the shell

Question 21

How many electrons can the first three electron

shells hold each?

Answer 21

2 electrons (first shell), 8 electrons (second shell), 18
electrons (third shell)

Question 22

What are the first four electron sub-shells

(orbitals) called?

Answer 22

s, p, d, and f (in order)

Question 23

How many electrons can each orbital hold?

Answer 23

a maximum of 2 electrons

Question 24

Define the term ionisation energy, and give its

unit

Answer 24

the energy it takes to remove a mole of electrons from a mole of atoms in the gaseous state, unit = kJ mol-1

Question 25

What is the equation for relative atomic mass

(Ar)?

Answer 25

relative atomic mass = average mass of 1 atom/

(1/12th mass of 1 atom of C12)