practicals Flashcards
Investigate how enzyme activity can be affected by changes in temperature
1) starch solution is heated to set temperature
2) amylase is added
3) iodine is added to each well after a minute
4) measure the time it takes until the iodine stops turning blue-black (this means that starch is not present as amylase has broken the starch down into glucose)
5) repeat the test with a different temperature
investigate diffusion in non-living systems
1) cut a 1cm3 cube of agar made of sodium hydroxide and phenolpthalein indicator
2) place cube in solution of hydrochloric acid
3) remove the cube and wash with water to stop futher reaction
4) cut the cube in half and measure the distance that the acid has caused the agar to become colorless from inside outwards
5) repeat the experiment two more times and calculate the mean
6) repeat with different concentrations of HCL
Investigate osmosis in potatoes
1) place different sucrose solutions including 0% for control, in different boiling tubes
2) dry potato strips on a paper towel and measure the masses
3) place each potato strip into each sucrose solution for 20 minutes and record how the mass changed
4) repeat tests at each solution several times with potato strips of similar masses
the evolution of oxygen
Take a bundle of shoots of a type of pondweed
Submerge them in a beaker of water underneath an 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
investigate the requirement for light in photosynthesis
De-starch the plant by placing it in a dark cupboard for 24 hours
This ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment
Following de-starching, partially cover a leaf of the plant with aluminium foil and place the plant in sunlight for a day
Remove the covered leaf and test for starch using the method below
Drop the leaf in boiling water
This kills the tissue and breaks down the cell walls
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so colour changes from iodine can be seen more clearly
Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol
Spread the leaf out on a white tile and cover it with iodine solution
investigate carbon dioxide and photosynthesis
De-starch the plant by placing it in a dark cupboard for 24 hours
This ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment
Following de-starching, enclose one leaf with a conical flask containing potassium hydroxide
The potassium hydroxide will absorb carbon dioxide from the surrounding air
Enclose another leaf with a conical flask containing no potassium hydroxide (control experiment)
Place the plant in bright light for several hours
Test both leaves for starch using iodine solution
Drop the leaf in boiling water
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
Rinse the leaf in cold water
Spread the leaf out on a white tile and cover it with iodine solution
investigate chlorophyll and photosynthesis
Drop the leaf in boiling water
This kills the tissue and breaks down the cell walls
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so colour changes from iodine can be seen more clearly
Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol
Spread the leaf out on a white tile and cover it with iodine solution
investigate the evolution of carbon dioxide from respiring seeds or other suitable living organisms
1) measure out 10 cm3 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/dead seeds 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
hydrogencarbonate indicator is red in atmospheric co2 levels:
- in high co2 levels the indicator reacts to co2 dissolving in water, which forms carbonic acid and changes the ph, causing it to become yellow
- in low co2 levels the lack of co2 makes the solution more alkaline, causing the color to shift to purple
investigate the evolution of heat from respiring seeds or other suitable living organisms
Flask A with the dead seeds
Flask B with the germinating seeds
Make sure the cotton wool is plugging the top of each flask
Hold the thermometer in place with the cotton wool
Invert the flask
Record the initial temperature
After 4 days, record the final temperature
