Devising Practicals and data

Question 1

What is the 5 point plan

Answer 1

5 point plan is
1-2 bullet points on how to change independent variable
1-2 bullet points on how to measure the dependent variable
DON’T STATE WHAT THEY ARE - must be quantitative
State 2-3 controlled variables
Why (if you didn’t what effect would it have on DV)
How (what piece of equipment and describe)
Describe suitable control e.g if using enzymes, use solution which has no enzyme to prove enzyme is having effect.
Repeat 5 times to calculate mean and appropriate statistical test

Question 2

What should you never say

Answer 2

Never say amount (say concentration/mass), always use at least 5 different concentrations and repeat 3x for each concentration.

Question 3

What should you do if controlled or independent variable is temp?

Answer 3

If controlled or independent variable is temp, use a water bath or an incubator

Question 4

What must you do with concentrations/temperature

Answer 4

With concentrations, you must repeat each concentration 3x and each temperature 3x

Question 5

What is a control

Answer 5

A control is used as a standard of comparison for checking results of an experiment. I.e check if it is really change in independent variable that is effect on dependent variable.
Version where you remove independent variable (sometimes you can’t e.g temperature - can’t remove temperature)

Question 6

How do control pH

Answer 6

Control pH with pH probe then add buffer to maintain pH

Question 7

How to analyse data

Answer 7

To analyse data,
Give overall trend (increase/decrease/remain same)
State if there is a linear or non linear
If non linear, go along x axis describing trend of each section
Quote figures from x axis independent (not y dependent)

Question 8

What do gradients of lines represent

Answer 8

Gradients of lines only represent rate of time is along x axis, so don’t refer to rapid or slow increase/decrease if there isn time. Instead say marked or slight increase/decrease

Question 9

What does “analyse graph to explain” mean

Answer 9

After each part of description (analysis of data) say “this is because”.
When answering a q with more than 1 table/graph/diagram, remember A and E, analyse (describe) and explain why
Refer to length and overlap of error bars
If a question says “explains relationship between”, still describe relationship

Question 10

How are repeats in studies using people achieved

Answer 10

Repeats in studies using people is achieved by having more people

Question 11

How to measure vitamin C content (in general)

Answer 11

Use pipette to Keep adding liquid to DCPIP (1% and 1cm^3), use titration to work out volume of liquid used, use vitamin C calibration curve to see how much vitamin C is in liquid