Practicals

Question 1

Describe an investigation to determine how temperature affects the activity of amylase. (6 marks)

Answer 1

*Add 5cm^3 of starch solution
*heat (water bath) until 20C
*Add iodine solution into separate wells of a spotting tile.
*use syringe and add amylase to the starch solution
*start timer
*at regular intervals (every 10 secs.) add amylase - starch to the iodine on the well of the tile
*Repeat this (every 10 seconds) until no more colour change
*Record the time taken for the reaction to be completed
*repeat twice at same temp.
*repeat investigation for diff temps.

Question 2

Model 5 marker - discuss the results of the enzyme activity investigation using his results. (5)

Answer 2

*At optimum temp. (data)
*the iodine stopped turning blue-black in the least amount of time (give data)
* enzyme is working at fastest rate and digested all starch in the solution
*At cold temp. (data)
* the iodine took a longer time to stop turning blue-black (data)
*As particles have less KE, less e.s.c
*At hot temp. (data)
*All tiles were blue-black (Data)
*As amylase denatured

Question 3

How do we edit the practical to investigate temperature on enzymes to PH. (1)

Answer 3

*Add 1cm^3 of PH buffer and don’t heat it.

Question 4

Describe a practical to investigate SA:V on diffusion. (5)

Answer 4

*pour phenolphthalein on agar cubes
*cut up pink cubes of agar to different dimensions (5cm)
*calculate the SA:V of each cube
*Pour of dilute hydrochloric acid into a beaker
*place the 0.5cm agar into the beaker
*start timer
*stop timer until cube turns colourless
*Repeat twice with same cube
*repeat investigation with different SA:V

Question 5

Describe how we can improve accuracy when investigating SA:V on agar. (2)

Answer 5

*use a ruler to cut cube
*as accurately as possible

Question 6

Describe practical for investigating osmosis in living organisms. (5)

Answer 6

*Use a cork borer to cut up 5 potato cylinders
*cut to about same length
*record mass of each cylinder
*measure 10cm^3 of 1.0M sugar solution and pour in test tube, label
*repeat step for different sugar solution conc. + distilled water
*add 1 potato cylinder to each test tube
*leave for 15 mins
*remove potato from tube and dry with towel
*measure new mass
*plot graph

Question 7

Describe practical for investigating osmosis in non -living organisms. (5)

Answer 7

*Tie one end of visking with string
*pour solution in tube
*insert one glass tube at one end
*mark the original water level in visking tube
*place tube in beaker of distilled water
*leave for 15 minutes
*note change in water level

Question 8

Suggest how a student can investigate the effect of light on net gas exchange in a leaf using hydrogen - carbonate indicator (H.C.I). (5)

Answer 8

*Set up beaker with water plant, water and H.C.I
*set lamp certain distance away
*leave plants for few minutes
*record colour of indicator
*repeat with different distances

Question 9

Describe a method the student could use to measure the effect of light intensity on rate of transpiration. (6)

Answer 9

*Set up a potometer underwater to remove air bubble in xylem
*place a lamp set distance from plant
*measure start distance of bubble
*after 10-15 minutes
*record distance moved by air bubble in capillary tube
*repeat for same light intensity
*repeat for different light intensities.
*keep control same.

Question 10

Design a practical a teacher can conduct to investigate starch production of a leaf. (5)

Answer 10

*cover half of small leaf with foil
*leave leaf on a windowsill for 2 days
*place leaf into boiling water to kill and preserve it
*place leaf into boiling ethanol to remove chlorophyll
*place leaf back into boiling water to soften it
*place leaf in a tile and cover with iodine solution
*covered part of leaf will remain orange - brown
*non - covered part will be blue - black.

Question 11

Design a practical to investigate the requirement of light in a plant. (5)

Answer 11

*place pondweed in water
*set up a desk lamp a set distance from the plant using a ruler
*leave for 5 minutes to allow plant to adapt
*count number of bubbles given off in 1 min and record
*repeat for different distances

Question 12

Design a practical to investigate the requirement of carbon dioxide in a plant, using sodium hydrogen carbonate indicator. (5)

Answer 12

*place pondweed in water
*add certain conc. of sodium hydrogen carbonate indicator
*leave for 5 minutes to allow plant to adapt
*count number of bubbles given off in 1 min and record
*repeat for different concentrations of sodium carbonate…

Question 13

Design a practical to investigate the requirement of chlorophyll in a plant. (5)

Answer 13

*use a variagated
*place leaf in boiling water to kill the leaf
*add leaf into hot ethanol to remove the chlorophyll
*rinse the leaf in cold water
*place leaf on a tile and add iodine solution
*white part of leaf will be orange - brown
*green part will be blue - black

Question 14

Design a practical to investigate the evolution of oxygen in a plant. (5)

Answer 14

*take bundle of shoot of a pondweed
*submerge them in beaker of water underneath upturned funnel
*Fill a boiling tube with water and place it over the end of the funnel
*As oxygen is produced, the bubbles of gas will collect in the boiling tube and displace the water
*test the gas with a glowing splint

Question 15

Describe an experiment the teacher can run to investigate the energy content in a food sample. (5)

Answer 15

*pour cold water into a boiling tube
*record starting temp. of water with a thermometer
*record mass of food sample on a scale
*heat food on Bunsen burner
*hold under boiling tube with water
*until it has completely burned
*record final temperature of water
*repeat with different food samples
*use formula Q=mc🔼T

Question 16

Describe a practical for investigating carbon dioxide from germinating seeds. (4)

Answer 16

*pour limewater into three boiling tubes
*then place a damp cotton wool in the bottom of another three tubes
*add 10 germinating seeds into one of them, 10 boiled seeds, nothing in the last one (control)
*connect each tube to different lime water tube
*leave overnight
*observe any colour change

Question 17

Give the colour of hydrogen carbonate indicator at high, normal and low CO2 concentrations. (3)

Answer 17

*high –> yellow
*normal –> orange/red
*low –> purple

Question 18

Describe a practical for investigating light intensity on gas exchange. (5)

Answer 18

*pour hydrogen carbonate indicator into 4 different boiling tubes
*place cotton wool above the indicator in each tube
*label each tube A-D
*in A place no leaf
*in B place leaf in bright light
*in C place leaf wrapped in aluminium
*place leaf in cotton cloth
*put bung on each tube
*leave all for 5-6 hrs
*record colour changes

Question 19

Investigate the conditions needed for germination. (5)

Answer 19

*set up 4 test tubes with 10 cress seeds on cotton wool
*Tube A - keep cotton wool dry, keep at 20C
*Tube B - moist the cotton wool, keep at 20C
*Tube C - add cooled boiled water and layer of oil, keep at 20C
*Tube D - moist cotton wool, keep at 4C (fridge)

only tube B will germinate

Question 20

Describe a practicle to investigate how temperature affects the rate of anaerobic respiration in yeast. (5 marks)

Answer 20

*Mix yeast with sugar solution in a boiling tube
*add a layer of vegetable oil to the top
*Using a capillary tube, connect this tube to a boiling tube with limewater
*Place these this apparatus in a water bath with a set temperature
*Count the number of bubbles produced in a fixed time
*Repeat with various temperature