practical skills

Question 1

define the term ‘hypothesis’

Answer 1

a testable statement of what we think will happen

Question 2

what is the purpose of an experiment?

Answer 2

to test whether or not a hypothesis is correct

Question 3

define the term ‘accurate’

Answer 3

close to the true/acceptable value

Question 4

define the term ‘precise’

Answer 4

results that are close together

Question 5

define the term ‘repeatable’

Answer 5

when repetition under the same conditions gives similar results

Question 6

define the term ‘reproducible’

Answer 6

when similar results are produced by performing the same/similar experiment in different conditions

Question 7

define the term ‘valid’

Answer 7

a suitable method is being used to answer the question being asked

Question 8

how can you ensure that an experiment is valid?

Answer 8

by controlling and defining variables

Question 9

define the term ‘independent variable’

Answer 9

what you change

Question 10

define the term ‘dependent variable’

Answer 10

what you measure

Question 11

define the term ‘control variable’

Answer 11

what you keep the same

Question 12

define the term ‘control’
(in an experiment)

Answer 12

a condition in the experiment that should have a known outcome

Question 13

define the term ‘negative control’
(in an experiment)

Answer 13

a control expected to show a negative result

Question 14

why are negative controls used?
(in an experiment)

Answer 14

to show if only the independent variable is affecting the dependent variable

Question 15

what does a change whilst a negative control is being used indicate?
(in an experiment)

Answer 15

that there is another, unknown factor or variable affecting the experiment

Question 16

define the term ‘positive control’
(in an experiment)

Answer 16

a control expected to show what a positive result looks like, by using a material/condition known to produce a positive result

Question 17

why are positive controls used?
(in an experiment)

Answer 17

to ensure that the experimental method can produce results when the expected outcome is present

Question 18

define the term ‘control group’, and why they are used
(in an experiment)

Answer 18

a group not given a particular treatment, that can be compared to individuals that have been given a treatment

Question 19

how many repeats should be performed for each condition
(in an experiment)

Answer 19

at least three replicates

Question 20

why should measurement of conditions be repeated?
(in an experiment)

Answer 20

to allow anomalies to be identified, and to calculate a mean - reducing their effect
as well as to assess precision and repeatability

Question 21

why is it useful to have a large sample size?
(in an experiment)

Answer 21

having as many participants as possible reduces the likelihood that results are due to chance

Question 22

why is calculating percentages of results useful?
(in an experiment)

Answer 22

can help compare amounts from samples of different sizes

Question 23

how do you calculate percentages?
(in an experiment)

Answer 23

(part / whole) x 100

Question 24

percentage change = ( ? / ? ) x100

Answer 24

[(new quantity - original quantity) / (original quantity)] x 100

Question 25

how can percentage change be used? (in an experiment)

Answer 25

to compare change when samples are different sizes

Question 26

what type of data is displayed as a bar graph?

Answer 26

qualitative, non-numerical data

Question 27

what type of data is displayed as a pie chart?

Answer 27

qualitative, non-numerical data

Question 28

what type of data is displayed as a line graph?

Answer 28

quantitative, continuous data

Question 29

what type of data is displayed as a histogram?

Answer 29

frequency data when the variable being measured is continuous but then separated into groups

Question 30

what are scattergrams/scatter plots used for?

Answer 30

to display the relationship between numerical values

Question 31

gradient = ? / ?

Answer 31

change in y / change in x

Question 32

how can you use a line graph to calculate a rate for the reaction, when the line of best fit is straight?

Answer 32

calculating the gradient of the line by dividing the change in y by the change in x

Question 33

what is the equation for a straight line?

Answer 33

y = mx + c

Question 34

how can you use a line graph to calculate a rate for the reaction, when the line of best fit is curved?

Answer 34

draw a tangent at the point on the curve you need to find the rate for and then calculate the gradient of that straight line

Question 35

what is the acronym for remembering the steps of graph plotting, and what does each letter stand for?

Answer 35

S - size of graph P - plotting L - line of best fit A - axes right way round T - title A - axis labels

Question 36

what does evaluating data include?

Answer 36

identifying anomalies/limitations calculating uncertainty/percentage error using standard deviation/statistical tests

Question 37

'when you take a reading using a piece of equipment, there is always some uncertainty in the reading' is this true or false?

Answer 37

true

Question 38

how can we reduce uncertainty?

Answer 38

using equipment with higher resolution

Question 39

error (uncertainty) = (?/?) x 100

Answer 39

absolute uncertainty / quantity measured

Question 40

if you have a measured distance between two values, you ? the uncertainty

Answer 40

double

Question 41

what is a random error?

Answer 41

an error in a measurement due to small uncontrollable effects - one-off mistakes made by the experimenters

Question 42

how can you reduce the effect of random errors?

Answer 42

taking more measurements and calculating the mean

Question 43

what is a systematic error?

Answer 43

an error due to the measured value differing from the true value by the same amount each time

Question 44

how can you avoid introducing systematic errors?

Answer 44

using the same equipment each time calibrating equipment

Question 45

define the term 'limitations'

Answer 45

issues with the practical procedure that could be improved

Question 46

give 2 examples of limitations in experiments

Answer 46

using equipment with a lower resolution not including repeats

Question 47

what should you include when you evaluate a method?

Answer 47

what is good about the method what could be improved/changed comment on validity

Question 48

what are the 3 ways to improve confidence in your results?

Answer 48

large sample size/more repeats repeatability statistical tests

Question 49

how can sample size/number of repeats be adapted to improve confidence in our results?

Answer 49

more repeats/larger sample size = more data, so if similar/same we can be more sure our results are correct

Question 50

how can statistical tests be used to improve confidence in our results?

Answer 50

can be used to see any relationship we see in our results is statistically significant therefore we can be more confident that our results are correct