Bridge Work

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 does an atom consist of?

Answer 15

a nucleus containing protons and neutrons, surrounded by
electrons

Question 16

What are the relative masses of a proton,
neutron, and electron?

Answer 16

1, 1, and 1/1840 respectively

Question 17

What are the relative charges of a proton,
neutron, and electro

Answer 17

+1, 0, and -1 respectively

Question 18

How do the number of protons and electrons
differ in an atom

Answer 18

they are the same because atoms have neutral charge

Question 19

What force holds an atomic nucleus together?

Answer 19

strong nuclear force

Question 20

What is the atomic number of an element?

Answer 20

the number of protons in the nucleus of a single atom of an
element

Question 21

What is the mass number of an element?

Answer 21

number of protons + number of neutrons

Question 22

What is an isotope?

Answer 22

n atom with the same number of protons but different
number of neutrons

Question 23

What is an ion?

Answer 23

an atom, or group of atoms, with a charge

Question 24

What is the function of a mass spectrometer?

Answer 24

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

Question 25

What is a mass spectrum?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

How many electrons can the first three electron shells hold each?

Answer 27

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

Question 28

What are the first four electron sub-shells (orbitals) called?

Answer 28

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

Question 29

How many electrons can each orbital hold

Answer 29

a maximum of 2 electrons

Question 30

Define the term ionisation energy, and give its unit

Answer 30

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

Question 31

What is the equation for relative atomic mass (Ar)?

Answer 31

= average mass of 1atom Over 1 twelfth mass of 1 atom carbon 12

Question 32

What is the equation for relative molecular mass (Mr)?

Answer 32

Average mass of 1 molecule Over 1/12th mass of 1 atom 12C