Pract

Question 1

Things to take note while writing tables

Answer 1

1. Indicate +- for increase, decrease
2. Standardise d.p.

https://docs.google.com/document/d/1sG942E4hsSUUBupFIWxzIaSQnrfX67mZtqmS5qHr5Cg/edit?tab=t.0 Page 1

Question 2

For anything regarding reaction speed, temperature round off to wat? why?

Answer 2

nearest second
(reaction time est 0.3s, impossible read, nearest 0.1s)

nearest 1deg celc
smallest division, thermometer

Question 3

Draw line graph if got obvious outlier then

Answer 3

1. plot (if within axes)
2. circle
3. label as (outlier)

https://docs.google.com/document/d/1sG942E4hsSUUBupFIWxzIaSQnrfX67mZtqmS5qHr5Cg/edit?tab=t.0 page 2

Question 4

axes need units?

Answer 4

no.

Marking Scheme

Axis
Scale
Coordinates
Line

Question 5

bar chart
things 2 take note

Answer 5

1. centralise label w/ bar
2. spaces btwn bars
3. same bar width
4. MUST START 0,0

https://docs.google.com/document/d/1sG942E4hsSUUBupFIWxzIaSQnrfX67mZtqmS5qHr5Cg/edit?tab=t.0 page 3

Question 6

histogram what to take note

Answer 6

1. X coord no need start w/ 0, Y coord MUST START 0
2. distinct categories
3. no data, dont plot anything

https://docs.google.com/document/d/1sG942E4hsSUUBupFIWxzIaSQnrfX67mZtqmS5qHr5Cg/edit?tab=t.0 page 4

Question 7

Specimen Errors
g__ v__

Answer 7

genetic variability
1. when obtained from different env
2. may be genetically different (diff conc. catalase)
3. cause inaccuracies in measurement and results
4. inaccuracies in final observation

obtain specimen, single organism/genetic lineage

Use when involve living organisms

1. When (experiment name), (?) obtained from different (?), that may be genetically different, result different (?, e.g. conc. of sucrose), causing inaccuracies in (what ure measuring), inaccuracies (final observation)

Question 8

Specimen Errors
o__ g__ d__ e__

1. format
2. how2 fix

Answer 8

1. When obtained from different organism,
2. may have grown diff env, varying (water availability)
3. cause inaccuracies in measurement and results (water potential)
4. inaccuracies in final observation

obtain specimen, single organism growing similar env

Use when involve living organisms

Question 9

Specimen Errors
s__ n__ h__

format
how2 fix

Answer 9

Suspension not homogeneous
1. When investigating (),
2. describe how suspension is used in experiment
3. suspension may not uniform, different density/conc/? of suspension.
4. inaccuracies measurement inaccuracies, final observation

stir stock b4 using

Use when involve suspensions

Question 10

analyse type qns

Answer 10

1. quote data
2. explain data

Question 11

application qns

Answer 11

> 1 mark -> must have link 2 syllabus

Question 12

draw enzyme-temp graph
label optimum temp, show your thinking

Answer 12

https://docs.google.com/document/d/1sG942E4hsSUUBupFIWxzIaSQnrfX67mZtqmS5qHr5Cg/edit?tab=t.0 page 5

Question 13

subjectivity
d__ o__ e__ p___

example
how 2 fix
format

Answer 13

definition of end point
1. change instrument/add apparatus, improve def, end point
2. in investigating (), end point determined by (),
3. (change in indicator not obvious),

end pt cannot determine accurately

Use when involve indicator

Question 14

surroundings errors

Answer 14

1. confounding factors, env
2. variability, env factors

no 1: use when investigating external factors affect rate of ___
no 2: use when investigating external factors affect rate of __

Question 15

surroundings errors
confounding factors, env
example
how 2 fix
format

Answer 15

change instrument, add apparatus, remove confounding factor

1. in investigating (),
2. (what cause confounding factor)
3. cause (variability of other variable)
4. hence over/underestimation, inaccuracies in

i.e. place beaker, water in front of lamp, absorb heat from lamp, allow light pass thru

Question 16

surroundings errors
variability, env factors
example
how 2 fix

Answer 16

evaporation, gravity, heat

change instrument, add apparatus, stabilise env factors

Question 17

set-up error
example
how 2 fix
format

Answer 17

i.e. yeast gas bubbles not all collected

investigating (),
(what cause inaccuracies)
hence under/overestimation of ()

Question 18

how improve accuracy vs improve reliability

Answer 18

accuracy
change apparatus/method
reliability
repeat expt. few times, obtain avg, omit any outliers from avg calculation

Question 19

movement of water molecules, visking tubing
things to take note

Answer 19

error
1. visking tubing, tied, prevent leakage, liquid
2. open end, visking tubing, above liquid lvl, beaker
3. osmosis occur, when outside visking tubing was washed, distilled water
4. gravity slows down mensicus

use of apparatus

3. partially permeable visking tubing, allow smaller molecules i.e. water pass thru, larger molecules i.e. sucrose cannot
4. distance moved, meniscus/mm per minute

Question 20

effect of conc., rate, osmosis on vegetable strip
things to take note

error
improvement

Answer 20

error
1. plant tissue, cut, identical dimension, keep sa:vol ratio constant
2. all plant tissue, submerge, liquid
3. petri dish cover, prevent evaporation
4. time each strip separately, avoid some strips submerged, slightly longer

improvement
1. different plants
2. diff env
3. varying water availability
4. cell sap, tissues, diff conc.
5. inaccuracies, rate, osmosis
6. change, diameter, strips

3. estimate, conc., plant cell sap
4. intersection of graph, no net movement of water

Question 21

caloric content of food sample (fire under food sample)
things take note

Answer 21

ensure
1. same vol, water used
2. same mass, food sample burnt
3. food sample, complete burnt
4. stopwatch, equal time, food sample allowed, burn

error
1. heat loss, surroundings -> not all heat energy released, increase temp, water, underestimation
2. distance between food sample, flame, always different

prevent source of error
1. cover test tube
2. weigh food sample

higher caloric content, burn larger flame, longer period time, more thermal energy released, increase temp, water, more

Question 22

how improve reliability

Answer 22

• repeat experiment 3x or more
• identify outliers, exclude, calculation, mean
• calculate mean

reduce effect outliers, increase reliability

Question 23

how improve accuracy

Answer 23

change instrument, measurement
mercury thermometer -> data logger w/ temp probe
measuring cylinder -> syringe

improve method, measurement
change, small time intervals instead longer time intervals

Question 24

enzymes expt. source of error

Answer 24

errors
1. pH buffer soln. 1cm^3, active enzymes, desired pH
2. surface of foam uneven, height different
3. potato slices, trap in froth
4. mass potato slices different, different amt o2 req float
5. temperature

improvement
1. potato tubers, diff plants
2. genetically different
3. different conc., catalase, potato discs

2h2o -(catalase)-> 2h2o + o2

catalase: many plant, animal tissues, break down hydrogen peroxide, simpler, less toxic substance

hydrogen peroxide: breakdown, produce o2, layer of froth, measure height, froth

Question 25

effect of (temp/pH/parameter) on rate of (enzyme) digestion expt. source of error

Answer 25

**iodine test error** 1. test carried out, __ minute intervals 2. could have been completely digested, any time btwn interval 3. overestimation, time taken 4. underestimation, rate, digestion **protein test error** never stir mixture **lipid test error** 1. change in colour, methyl orange indicator, gradual 2. end point not determined accurately 3. inaccuracies, measurement, time taken, digestion 4. use pH meter, indicate pH when indicator turn colourless, stop stopwatch when pH meter read exact pH **apparatus usage** **starch, iodine** extract 1 drop reacting mixture, mix w/ one drop iodine soln, time where iodine soln. no longer turn blue black, completely digested **pepsin/trypsin** protein insol. water, cloudy suspension reacting mixture clear, protein completely digested **lipase** fatty acids acidic, reduce pH methyl orange, orange -> red ## Footnote never stir mixture for test for sugar/starch e.g. involving leaf - leaves exposed to light, already photosynthesised before expt. begun

Question 26

plant immersed in sodium hydrogencarbonate soln. light intensity expt. error apparatus sodium hydrogencarbonate soln for what?

Answer 26

**error** - reduce distance lamp, - increase temp, - (**place beaker of water, absorb heat energy, heat shield**) - surrounding light affect results, overestimation ## Footnote **apparatus** sodium hydrogencarbonate: source of co2, adjust mass, sodium hydrogencarbonate powder dissolve, more hydrogen carbonate ions

Question 27

algal bead expt. what to count, rate of photosynthesis? what cause algal beat float? how light intensity limiting factor?

Answer 27

**what to count to determine rate of photosynthesis?** water plant: gas bubbles formed per unit time algal bead/leaf disc: time taken, half no., algal bead/leaf disc float **what cause algal bead float?** o2 gas released, photosynthesis, increase buoyancy **how light intensity limiting factor?** - light intensity low, light intensity limiting factor, rate of photosynthesis, - light intensity increases, rate photosynthesis increases - light intensity high, photosynthesis nvr further increase, light intensity no longer limiting factor ## Footnote limiting factor may be... **if use (aq) KMno4, can say color change subjective

Question 28

algal bead source of error

Answer 28

- not all beads formed may be equal size - no stirring, suspension, not homogenous

Question 29

destarch a plant

Answer 29

keep plant, dark cabinet, 48h

Question 30

decolourise leaf, test 4 starch

Answer 30

- heat leaf, boiling water 5min (denature enzymes) - warm leaf, ethanol, 10min, leaf turn colourless (dissolve lipids, cell surface membrane, chloroplasts diffuse, see iodine test results clearer) - transfer leaf, warm water (soften leaf, disrupt cuticle, cell wall, easier spread out, white tile) - transfer **white tile**, iodine soln.

Question 31

transport of dyed water, xylem expt. what dyed water used for? how water move up?

Answer 31

**dyed water** allow visualisation, position of xylem vessels, movement of water thru it **move up** capillary movement

Question 32

production of co2 during respiration (germinating seeds) expt control set-up?

Answer 32

**control** - small pebbles, prove change in pH not due to atmospheric co2 dissolve, pH indicator - boiled seeds, prove co2 not produced, seeds dead/enzymes denatured

Question 33

yeast respiration expt. (plunger submerged in water bath) source of error how does yeast respire? optimum temp?

Answer 33

**error** - nozzle syringe sealed, prevent gases, yeast leak out - yeast, glucose mixture submerged, water bath - no stirring, not homogenous soln - no stirring, not aerated, not enough o2, rate of aerobic respiration lower, expected **respire** anaerobically and aerobically **optimum temp** 40 deg celc like mammals

Question 34

test urine sample for nutrients expt. healthy individual? what if glucose, proteins found?

Answer 34

healthy individuals: negligible glucose/protein glucose: diabetes mellitus protein: kidney disease, kidney cortex damaged, basement membrane lost integrity

Question 35

thermometer, hot water and wrapping tissue paper around can rate of heat loss expt. source of error

Answer 35

**source of error** - volume water, initial temp, both cans same - no heat source near ## Footnote draw tangent to curve to find gradient

Question 36

nervous system expt. pins which part most sensitive to touch?

Answer 36

palm most sensitive, highest density, touch receptors, elbow least sensitive

Question 37

blind spot expt. why dot disappear when one eye open? why dot wont disappear when both eye open?

Answer 37

1. image fell, blind spot, __ eye no photoreceptors 2. both eyes open,dot wont disappear, two blind spots do not coincide, image, one blind spot, fall on photoreceptors, other eye

Question 38

magnification to wat dp

Answer 38

1dp

Question 39

cont, discont variation, use bar graph or histogram represent?

Answer 39

cont: histogram discont: bar chart

Question 40

how to calculate rate of reaction

Answer 40

**check time** - if time 2 digit - 100/t - if time 3 digit - 1000/t

Question 41

planning

Answer 41

1. independant variable, how adjust (range of 5) 2. dependant variable, how measure 3. 2 variables constant, how keep constant 4. repeat 3x, **calculate avg, dependant variable** 5. plot graph of __ against __ (**units**) 6. If... then... (**interpret result**) 7. bonus: shake well to mix (**suspensions,need shaking**) 8. bonus: in the dark, make sure clamp nvr cover plant (**photosynthesis**) ## Footnote **ALWAYS ADD CONSTANT VARIA**

Question 42

planning when involve temp

Answer 42

put into water bath of (deg), wait for 5min ## Footnote need time for set-up to cool/heat to desired temp

Question 43

how to improve counting bubble

Answer 43

connect to calibrated gas syringe ## Footnote DONT USE: DISPLACEMENT OF WATER - must explain if uw use

Question 44

when use syringe when use cylinder

Answer 44

syringe: precise volumes, small volumes MC: water bath

Question 45

sodium hydrogencarbonate + hydrilla and syringe expt. why mensicus move

Answer 45

- oxygen produced, photosynthesis, increase volume air, syringe - decrease pressure, liquid, capillary tube, result in movement

Question 46

sodium hydroxide absorb co2?

Answer 46

yes react w/ co2

Question 47

submerge leaf in warm water observation

Answer 47

bubbles appear, both surface, leaf more bubbles appeared on (what) surface of leaf

Question 48

best fit line

Answer 48

https://docs.google.com/document/d/1LQacTU0A416kWYxp3Du0-mVf9HBosNswJ_jQ2zTk5X0/edit?tab=t.0 page 39

Question 49

graph paper

Answer 49

- each small square 1mm - draw margin of () - count squares making up, area, which occuoy more than () of squares ## Footnote measure if can

Question 50

when to quote highest, lowest data points when to quote highest/lowest difference relative to other differences? when to quote outlier?

Answer 50

**highest/lowest data** - curves **highest/lowest difference** - line - describe data - must talk relative to other points - 0.6 million increase in year 1 (**largest**), but all other years 0.4million increase **outlier** - when very very off

Question 51

cont. variation discont. variation e.gs

Answer 51

cont: diameter, fruit, mass, seedling discont: colour, flower

Question 52

how prepare microscope slide

Answer 52

- cut thin slice - drop, iodine soln - stain sample, make it easier to see () - use cover slip, cover the slide - remove air bubbles - clean excess stain - focus lens, microscope

Question 53

how tell something is cell wall/CSM

Answer 53

cell wall: double line, perimeter CSM: single line, perimeter

Question 54

why put everything in water bath for 5 min before expt.

Answer 54

reach equilibrium of temp. **incubate in separate test tube

Question 55

variables kept constant

Answer 55

- temperature - conc. (of soln., of indicator) - volume (no of drops, indicator) - mass - time - same (living sample, includes people) - pH - level of agitation/activity level (living)

Question 56

variation expt. source of error

Answer 56

sample size small - results not representative, whole population - increase sample size

Question 57

accuracy for burette measuring cylinder electronic balance ruler syringe

Answer 57

0.05cm^3 0.5cm^3 1dp OR 2dp 1dp 1dp

Question 58

density rate units

Answer 58

g/cm^3 /s

Question 59

describe 2 ways, how you use syringe, ensure dilutions made accurately

Answer 59

- remove bubbles, syringe, invert syringe, tap it - use syringe, slightly larger volume

Question 60

proper handling of apparatus

Answer 60

- dont cross contaminate - wash all apparatus, distilled water

Question 61

why calculate percentage, length

Answer 61

- different __, different initial lengths - %tage change, accurately reflect, how much ____, shrunk, increase in size, compare how they were like, beginning

Question 62

table first column is always

Answer 62

independant variable subsequent columns, dependant ## Footnote i.e. investigating how conc. of sucrose affect length of potato conc. of sucrose soln occupies first column

Question 63

hydrogencarbonate indicator usage

Answer 63

usage: indicate level of co2 conc. in soln.

Question 64

safety hazards

Answer 64

- ethanol: flammable - hydrogen peroxide: corrosive - acids, alkalis, indicator: irritant - hot water bath: danger of scalding - scalpel: cut

Question 65

how improve accuracy when involving soln.

Answer 65

conduct expt. w/ soln. that have closer conc. to each other ## Footnote - intervals are too large - carry out expt with () conc. of (nearer intervals)

Question 66

how to minimise safety hazard

Answer 66

- point test tube away when heating - use lab coat - wear goggles - wash off any split chemical - use forceps, test tube holder (**prevent indicator/chemical/hot water e.g.**) - use scalpel, stable surface, white tile - handle sample w/ forceps, avoid contact w/ scalpel ## Footnote no direct heating

Question 67

why leave expt. at (condition except for temperature) for 5min?

Answer 67

Allow () to get used to (condition) ## Footnote i.e. allow hydrilla to get used to new light intensity

Question 68

prepare solution must do...

Answer 68

shake mixture

Question 69

planning involving live object

Answer 69

use the **SAME** ()

Question 70

when use magnifying glass

Answer 70

closer look, specimens (but not cellular level)

Question 71

how turgidity -> flexibility

Answer 71

more turgid, more turgor pressure, limit movement, contents decrease flexible

Question 72

how improve expt. that has very close results to each other

Answer 72

use more time, more obv difference