practical

Question 1

independent variable

Answer 1

I change

Question 2

Dependent variable

Answer 2

Data

Question 3

Controlled variable

Answer 3

not IV/DV

Question 4

why not “amount”?

Answer 4

vague! use spec (time/volume/mass/weight etc)

Question 5

why food solution > actual food sample used?

Answer 5

1. allow nutrients to dissolve
2. colour of food when in solution will not interfere with observations for results

Question 6

why not use dropper? what to replace it with?

Answer 6

not precise bc it’s graduated! use syringe!

Question 7

IMPT TO LIGHT BUNSEN BURNER

Answer 7

CLOSE airhole!!

Question 8

is parallax error a source of error? why/why not?

Answer 8

no!
it’s a human error which can be avoided with carefulness so it’s a precaution instead

Question 9

what does “decant” mean?

Answer 9

leave sediments behind, only liquids to transfer

Question 10

(for bio drawings) what should the lines look like? what about shading?

Answer 10

clear, continuous. NO shading

Question 11

(for bio drawings) need labels? how not to draw?

Answer 11

depends if asked for, NO cutting across most of drawing

Question 12

(for bio drawings) magnification calculation?

Answer 12

x (drawing size cm/life size cm)

Question 13

(for bio drawings) how to ensure accuracy?

Answer 13

visible details

Question 14

(for bio drawings) how to ensure proportions?

Answer 14

features drawn to relative size

Question 15

(tables) how not to draw lines?

Answer 15

no 出头, no blank cells

Question 16

(tables) when to draw them?

Answer 16

before experiment!

Question 17

(tables) stationery for lines & data?

Answer 17

lines - pencil
data - pen

Question 18

(tables) heading rules?

Answer 18

1. SI units so body doesn’t have units
2. leftmost column to right:
   a. IV (food sample)
   b. test name
   c. raw data (observations bc qualitative data)
   d. processed data (conclusions drawn from raw data)

Question 19

(tables) cells rules?

Answer 19

1. use + & - for changes in readings
2. no units

Question 20

can write “no change observed”?

Answer 20

no! use “solution REMAINED (original state/colour)”

Question 21

experimental errors don’t include human errors like? key gist?

Answer 21

1. reading/using instruments wrongly (zero error & parallax error)
2. not following instructions
3. carelessness
4. humanness (reaction time delay)
   BIOLOGISTS ARE SUPERHUMAN

Question 22

experimental errors mean?

Answer 22

inherent in process, cannot be eliminated simply by repeating carefully, but only minimised

Question 23

experimental errors answering structure?

Answer 23

1. source of error
2. impact on experiment (results inaccurate)
3. improve to minimize/avoid error

Question 24

subjectivity causes inaccurate results?

Answer 24

determine colour intensity achieved

Question 25

improve to determine colour intensity achieved?

Answer 25

compare test sample result against colour chart OR use colorimeter to quantitatively measure colour intensity of sample

Question 26

inaccurate comparisons on nutrient content btwn food samples?

Answer 26

starting mass of food samples used not kept constant OR using dropper to measure out 2cm^3 of food solution being imprecise OR volume of water added to dissolve food samples not kept constant

Question 27

improve to starting mass of food samples used not kept constant?

Answer 27

crush food sample and weight out fixed mass for testing

Question 28

improve to using dropper to measure out 2cm^3 of food solution being imprecise?

Answer 28

replace dropper with syringe which gives out more precise measurements

Question 29

improve to volume of water added to dissolve food samples not kept constant?

Answer 29

use measuring cylinder to measure out exactly same volume of water for both samples

Question 30

(DEPENDS) inaccurate results?

Answer 30

degree of swirling/mixing with glass rod not consistent so different extents of nutrients dissolving into solutions

Question 31

(DEPENDS) improve to degree of swirling/mixing with glass rod not consistent so different extents of nutrients dissolving into solutions?

Answer 31

swirl/stir for exactly 10 times OR place mortar on mechanical shaker for fixed duration for equal mixing