U3AOS1: scientific skills

Question 1

define aim

Answer 1

purpose/objective of an experiment
usually starts with ‘to determine’ or ‘to investigate’

Question 2

define independent variable

Answer 2

the variable that is deliberately manipulated or changed by the experimenter -> should be only one variable to increase validity of data collected

Question 3

define dependent variable

Answer 3

variable that is measured by experimenter to determine if change in IV had any effect

Question 4

define controlled variable

Answer 4

variables that remain constant throughout the experiment -> important b/c ensure they don’t impact the validity of the data collected in the experiment

Question 5

define hypothesis

Answer 5

a testable statement which predicts the outcome of an experiment/investigation

Question 6

hypothesis formula

Answer 6

if the dv…. [phrase outline r’ship between dv and iv] … then … [trend indicating effect on the dv] … when … [trend indicating action by the iv]

Question 7

define quantitative

Answer 7

analysis - identifies the amount of a substance present
data - provides a numerical value

Question 8

define qualitative

Answer 8

analysis - technique that determines the composition of the sample
data - descriptive data collected based on observations

Question 9

what is a systematic error

Answer 9

a consistent error which causes measured values to be skewed by a consistent amount every time -> affects accuracy eg. uncalibrated equip, parallax error

Question 10

how to manage systematic errors

Answer 10

-measuring apparatus used should be calibrated prior to experiment
-change the experiment eg. using a quality primary standard

Question 11

what is a random error

Answer 11

-unpredictable variations resulting in a spread of measurements
-differs in amount/proportion each time bc ‘one-off’ error
-affect precision
-eg. subjective judgements made/estimate measurement that falls between lines of burette

Question 12

how to manage random errors

Answer 12

effect minimised by repeating measurements multiple times -> increased reliability, and calculate average of the results obtained, omit outliers

Question 13

what is a personal error

Answer 13

results of mistakes made by the experimenter when misinterpret information eg. miscalculations, misreading scales

Question 14

how to manage personal errors

Answer 14

repeating the experiment in the correct manner -> they are avoidable errors

Question 15

define reliability + how to improve

Answer 15

refers to whether or not consistent results can be achieved when conducting the same experiment under varying conditions

improved by repeating experiment + averaging results

Question 16

define repeatability + how to improve

Answer 16

how close measured values are from repeated experiments conducted using the same method, under the same measuring conditions by the same experimenter

improved by the use of precise equipment and ^ no. of measurements taken

Question 17

define reproducibility + how to improve

Answer 17

describes the closeness of values measured from repeated experiments under different conditions eg. changes in equipment, environment, experimenter but ^ chance of random errors with more changes

improved by use of precise apparatus and increasing no. of measures

Question 18

define validity

Answer 18

the extent to which an experiment investigates what it aims or claims to. results can answer aim/hypothesis. this is affected by both experimental design (eg controlled variables) and how it is conducted (eg observer bias).

internal = experimenter did everything right
external = confounding factors?

Question 19

define accuracy

Answer 19

how close a measured value is to the true value of the quantity being measured

Question 20

define precision

Answer 20

how closely two or more measurement values are in agreement with each other

Question 21

define resolution

Answer 21

the smallest change in the quantity being measured that results in a perceptible change on the measuring instrument. eg. the resolution of a burette is 0.05 mL

Question 22

define outliers

Answer 22

data points or observations that differ significantly from other data points or observations -> caused by mistakes so should be omitted, but must be accounted for before omission as an ethical approach to dealing with data

Question 23

suggest why experiments are repeated

Answer 23

-to minimise impacts of random errors by taking on an average of the results obtained
-allows for experimenter to check that method is reliable/reproducible

Question 24

what should you always link reliability to?

Answer 24

repeating experiment

Question 25

safety concerns w cl2, NaOH, H2 gas

Answer 25

H2 = highly flammable and can result in explostion
Cl2 = toxic
NaOH = corrosive

Question 26

aspects that should be included in discussion part of poster relating to experiment

Answer 26

-limitation/errors
-whether the date supports or refutes the hypothesis
-relating experiment to earlier work / theory