practical skills

Question 1

what is the purpose of controlled factors? give an example

Answer 1

factors must be kept the same to ensure that results are only affected by the independent variable
e.g temp, pH, conc. of enzyme and substrate etc

Question 2

what is a control experiment?

Answer 2

everything is kept the same except swap the independent variable with an inactive substitute

Question 3

what is the purpose of a control experiment? give an example

Answer 3

shows that the independent variable causes the dependent variable to change
e.g use a placebo in drug trials/ boil the enzyme in enzyme experiments

Question 4

what is the purpose of repeats? give an example

Answer 4

allows a more reliable mean to be calculated and allows anomalies to be identified
e.g take 20 quadrant sites in ecology, using 5 reactions at each temp in an enzyme practical

Question 5

what is the ‘accuracy of data? give an example

Answer 5

how many decimal places you are able to measure to
e.g volume markings on a syringe, decimal places on a mass balance

Question 6

what affects the accuracy of a line of best fit? give an example

Answer 6

data points/ more data points allow greater accuracy of where you draw the line
e.g more temperature experiment for enzyme prac./. more concentrations of sucrose for osmosis practical.

Question 7

how can you regulate temperature and pH in a practical? give an example

Answer 7

use a thermometer or pH meter to check regularly and say what action to take if needed
e.g check thermometer every 2 minutes and add hot water if the temp. is too low

Question 8

what is the difference between raw and processed data? give an example

Answer 8

raw data is the results you measure as the dependent variable, processed data is the data that you then calculate from these
e.g time taken for a reaction to occur vs the rate of reaction you calculate as 1/time