Practicals Flashcards
What does the practical investigating the effect of changing temperature on enzyme activity involve?
1) Heat a starch solution to a set temperature (eg 30C), using a bunsen burner/ water bath
2) Prepare a spotting tile, add a few drops of iodine solution to each well
3) Once starch solution is at desired temperature, add enzyme amylase, which will digest starch
4) Time it, after a minute add a sample of the starch solution into the first well of the tile
5) At 30C, the starch won’t have all been digested yet so there will be a colour change to blue/black
6) Every minute, add a small sample of the same starch solution to the next well, eventually, there will be a timer where all the starch has been digested and there is no longer a colour change
7) Repeat at different temperatures
How do you investigate osmosis using living systems?
Submerging potato cylinders in different concentrations of sugar/salt solutions and measuring change in mass.
1) Use a cork borer to cut 5 potato cylinders of same diameter
2) Use a scalpel and ruler to trim each cylinder so they are same length
3) Measure mass of each cylinder and record table of results
4) Measure equal volumes of salt/sugar solution into boiling tubes, put a cylinder in each and label each tube
5) After 1 hour, remove cylinders, blot dry and record final mass
How do you investigate osmosis using non-living systems?
1) Tie one end of a visking tube with a piece of string
2) Pour some solution into the visking tube
3) Insert a capillary tube into one end of the visking tube. Close the other end of the visking tube by tying with another piece of string
4) Mark initial water level in visking tube
5) Use a stand and clamp to fix position of capillary tube, immerse visking tube in a beaker of distilled water
6) leave for 15 minutes
7) Note difference in water level in capillary
How do you investigate diffusion using non-living systems?
1) Place a few potassium permanganate crystals in a beaker of water
2) Note the colour of the water after a period of time eg. 15 minutes
3) Note the colour of the water after a longer period of time eg. 1 hour
- Potassium permanganate molecules diffuse from a region of high concentration (crystal) to a
region of low concentration (surrounding water).
After a short period of time, the molecules are still diffusing throughout the surrounding water and
is not equally distributed so the colour is not uniform.
The molecules will diffuse throughout the water until it reaches equilibrium, hence, over time, the
colour of the water will be a uniform pale purple.
What does the practical investigating the need for light in photosynthesis involve?
1) De-starch the plant:
-place in a dark cupboard for 24 hours
-this ensures any starch already present is used up
-partially cover a leaf of the plant with aluminium foil and place the plant in sunlight for a day
2) Test leaf for starch
-drop leaf in boiling water
-transfer leaf into hot ethanol in a boiling tube for 5-10 minutes, this removes chlorophyll so colour changes from iodine can be seen more clearly
-rinse the leaf in cold water
-spread leaf out on white tile and cover it with iodine solution
3) Results
-In a green leaf, the entire leaf will turn blue-black as photosynthesis occurs in all areas of the leaf
-areas covered with aluminium foil will remain orange-brown as it did not receive sunlight so could not photosynthesise , while area exposed to sunlight will turn blue-black
What does the practical showing the evolution of oxygen from a water plant involve?
1) Take a bundle of shoots of a water plant
2) Submerge them in a beaker of water underneath an upturned funnel
3) Fill a boiling tube with water and place it over the end of the funnel
4) As oxygen is produced, the bubbles of gas will collect in the boiling tube and displace the water
5) Show that the gas collected is oxygen by relighting a glowing splint
What does the practical investigating the need for carbon dioxide in photosynthesis involve?
1) De-starch the plant by placing it in a dark cupboard for 24 hours, so present starch is used up
2) Then enclose one leaf with a conical flask containing potassium hydroxide, this will absorb CO2 from surrounding air
3) Enclose another leaf with a conical flask containing no potassium hydroxide (control)
4) Place the plant in bright light for several hours
5) Test both leaves for starch (boiling water, hot ethanol rinse with cold water, test using iodine solution)
-Leaf with potassium hydroxide will stay orange as no starch is produced, leaf without it will turn blue/black
What does the practical investigating the need for chlorophyll in photosynthesis?
1) Drop the leaf in boiling water to kill the tissue and break down cell wall
2) Transfer leaf to hot ethanol in a boiling tube for 5-10 minutes to remove chlorophyll
3) Rinse the leaf in cold water to soften the leaf tissue after being in ethanol
4) Spread leaf out on a white tile and cover with iodine solution
-The white areas of the leaf containing no chlorophyll stay orange-brown
How can you investigate the evolution of carbon dioxide from respiring seeds?
1) Measure out 10cm3 of hydrogencarbonate indicator into 3 boiling tubes
2) Put in a layer of cotton wool
3) Place 10 germinating seeds in tube A
4) Place 10 boiled seeds (dead) in tube B
5) Place 10 glass beads in tube C
6) Seal each tube with a rubber bung
7) After 3 hours, observe the colour of the indicator
-Tube A should turn yellow as respiring seeds produce carbon dioxide
-Tube B should turn orange as seeds won’t produce carbon dioxide as well as tube C
How can you investigate the evolution of heat from respiring seeds?
1) Set up 2 vacuum flasks, one with dead seeds (boiled), one with germinating seeds
2) Soak both sets of seeds in milton keans solution to kill bacteria
3) Make sure the cotton wool is plugging the top of each flask
4) Hold the thermometer in place with the cotton wool
5) Invert the flask
6) Record initial temperature
7) After 4 days, record the final temperature
How can you investigate the energy content of a food sample?
1) Add 25cm3 of water to a boiling tube
2) Measure the initial temperature of water and record it
3) Weigh the food sample and skewer it on the needle
4) Light a Bunsen burner away from the boiling tube and light the food sample in the flame
5) Place the burning food sample under the boiling tube. If it goes out, relight it and place it
back under the boiling tube until it will not relight
6) Record the final temperature of the water
7) Calculate the energy content of the food using the formula:
energy (J) = mass of water (g) x temperature change (°C) x 4.2 (J °C-1 g-1)
How can you investigate breathing in humans including the release of carbon dioxide?
1) Pour some limewater into a boiling tube
2) Using a straw, breathe air into the limewater
3) Note the change in the limewater. Lime water turning cloudy indicates the presence of
carbon dioxide
How can you investigate breathing in humans including the effect of exercise?
1) Measure and record the breathing rate (number of breaths per minute) of the participant at
rest
2) Carry out a specific exercise (eg. running/jumping) for a fixed period of time eg.1 minute
3) Measure the breathing rate of the participant again
How can you investigate the role of environmental factors in determining the
rate of transpiration from a leafy shoot?
1) Cut shoot underwater to prevent air from entering Xylem and place through hole to stopper provided with potometer
2) Fill potometer with water and fit the stopper holding the leafy shoot to apparatus
3) Use vaseline to seal apparatus to ensure equipment is airtight
4) Trap air bubble in capillary tube by dipping end of capillary tube into beaker of water, then close reservoir tap and remove beaker of water, then re-immerse capillary tube into beaker
5) Measure and record the starting distance of air bubble
6) Change environmental factor being investigated
7) Allow shoot to adapt to new environment for a fixed period of time
8) Measure and record the final distance of air bubble to calculate the total volume of Water absorbed by plant
9) Change intensity of environmental factor and repeat process
Hw can you investigate the conditions needed for seed germination?
1) Set up 4 different test tubes, each with cotton wool at bottom and 5 cress seeds:
-Test tube A: moist cotton wool and placed in warm environment
-Test tube B: dry cotton wool and placed in warm environment
-Test tube C: moist cotton wool and is placed in cold environment
-Test tube D: cotton wool soaked in boiled Water that is cooled off, and layered with oil on top
2) After all test tubes are set up, Cress Seeds in each respective test tube is allowed to adjust to new environment for a fixed number of days
3) After a fixed number of days has passed, results are compared via:
-Number of Cress Seeds germinated
-Height of Germinated Seed
