All practicals iGCSE Flashcards
practical: investigate food samples for the presence of glucose
- Add a few drops of Benedict’s solution into test tube of test solution
- Heat test tube placed in a water bath set at 60 - 70 °C for 5 minutes
- Remove test tube from water bath and observe colour change
- If Glucose is present, solution will turn brick red
- If Glucose is not present, solution will stay blue
practical: investigate food samples for the presence of starch
- Use pipette to transfer sample solution into wells on tile
- Add a few drops of Iodine solution and observe colour change
- If Starch is present, solution will turn blue-black
- If Starch is not present, solution will stay brown
practical: investigate food samples for the presence of fat
- Test tube of sample solution is mixed with 2cm3 of Ethanol and 2cm3 of distilled water
- Observe colour change
- If Fat is present, a milky - white emulsion will form
- If Fat is not present, solution will remain colourless
practical: investigate food samples for the presence of protein
- Add a few drops of Biuret solution into test tube of sample solution
- Observe colour change
- If Protein is present, solution will turn violet
- If Protein is not present, solution will stay blue
practical: investigate how enzyme activity can be affected by changes in temperature
The experiment consisted in iodine and adding amylase solution to each circle of iodine every 30 seconds. We must have seen that the higher temperature (60-90) didn’t work because enzymes were denatured and the lower temperature (0-20) didn’t work because the enzymes didn’t have much kinetic energy and didn’t collide fast enough with the active site
practical: investigate diffusion using living and non-living systems
Put different sizes of agar cubes (10mm, 8mm, 6mm, 4mm and 2mm) into hydrochloric acid and time it until the agar cube has compleatly turned transparent. The results are that the smaller cubes turned transparent quicker than the bigger.
practical: investigate osmosis using living and non-living systems
Put different potato masses cylinders in sucrose solutions with different concentrations. The more concentrated solution will loose mass as the water moves from high to low concentration. In the more dilutes solution the other way around, it will increase in mass as the water moves from a high to low concentration of water.
practical: investigate photosynthesis, showing the evolution of oxygen from a water
plant, the production of starch and the requirements of light, carbon dioxide and
chlorophyll
Pondweed is placed in water, as photosynthesis is carried out oxygen is made and we can see it through bubbles. Factors that affect rate of photosynthesis: Light intensity, carbon dioxide concentration, chlorophyll in leaves and temperature. As the lamp is moved closer there is more oxygen being made (bubbles).
2.39 practical: investigate the evolution of carbon dioxide and heat from respiring seeds or
other suitable living organisms
- Measure out 10 cm3 of hydrogencarbonate indicator into 3 boiling tubes
- Put in a layer of cotton wool
- Place 10 germinating seeds in tube A
- Place 10 boiled/dead seeds in tube B
- Place 10 glass beads in tube C
- Seal each tube with a rubber bung
- After 3 hours, observe the colour of the indicator
-Hydrogencarbonate indicator is orange in atmospheric CO2 levels
-In high CO2 levels the indicator absorbs the CO2 and becomes yellow
-In low CO2 levels it loses CO2 and becomes purple
practical: investigate breathing in humans, including the release of carbon dioxide
and the effect of exercise
- Measure a fixed volume of Limewater into a boiling tube
- Use a straw and blow into the solution of Limewater
- Limewater turns cloudy when Carbon Dioxide is present
- Hence, as respiration produces Carbon Dioxide as a waste product, blowing into a solution of Limewater will form a cloudy solution, therefore showing the production of Carbon Dioxide via respiration
- Stationary breathing rate of participants is recorded
- Specific exercise will be performed by participants at the same intensity for a fixed period of time
- Breathing rate after exercise is recorded
- Results are compared
practical: investigate the conditions needed for seed germination
- Cotton wool is placed at the bottom of four boiling tubes, each containing five Cress Seeds
- Each test tube is then individually set up:
- Test Tube A: moist cotton wool and placed in warm environment (hot water bath set at appropriate temperature)
- Test Tube B: dry cotton wool and placed in warm environment (hot water bath set at appropriate temperature)
- Test Tube C: moist cotton wool and is placed in cold environment (bucket of ice)
- Test Tube D: cotton wool soaked in boiled Water that is cooled off, and layered with Oil on top
- 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
- After a fixed number of days has passed, results are compared via:
- Number of Cress Seeds germinated
- Height of Germinated Seed
practical: investigate the population size of an organism in two different areas using
quadrats
- Place quadrat randomly within sampling area
- Count the number of members of the same specieswithin the quadrat
- Repeat this numerous times within sampling area using the same size quadrat
- Repeat the process in another area to compare results
Population size = (total area/ sampled area) * numer of organisms
practical: investigate the role of anaerobic respiration by yeast in different conditions
- Mix boiling tube of Sugar solution with Yeast, covering it with a layer of Oil to prevent the entry of Oxygen; hence, ensuring aerobic respiration
- Boiling tube is connected to a test tube of Limewater via capillary tube that is kept airtight by a bung
- Boiling tube of Sugar solution with Yeast is placed in a Water bath of set temperature
- Rate of Carbon Dioxide production is measured by number of bubbles produced in a fixed time in test tube of Limewater
- Compare results obtained at different temperatures
- As temperature increases towards optimum, the rate of Carbon Dioxide production will increase
- This is because the increase in temperature towards optimum will allow optimum enzyme activity for Yeast enzymes, hence increasing the rate of Anaerobic respiration to produce Carbon Dioxide (and Ethanol)
- However, as temperature increases above optimum, enzymes involved in Anaerobic respiration will denature, therefore causing the rate of Carbon Dioxide production to decrease
