RP4 Flashcards
(11 cards)
How do you calculate percentage uncertainty?
% error = error / measured value x 100
You were provided with beetroot discs that were washed thoroughly before the start of the investigation. Explain why it was important to wash the beetroot discs.
To wash off/ remove any excess pigment.
In part 2 of this investigation you used 5 concentrations of alcohol.
Describe a suitable control for your investigation.
Put beetroot discs in water filled test tube.
Explain why you instructed to shake the test tubes every minute.
• Tp prevent the beetroot discs from sticking together.
• Maintains a diffusion gradient for the pigment.
Explain why you were instructed to pour the alcohol immediately from the experimental test tube into a clean test tube.
• So no more pigment can diffuse out of the discs
• To limit variation in time that the discs are in the alcohol.
You were given discs taken from fresh beetroot on your investigation. Explain why your results would have been different if you used cooked beetroot.
• Heating/ cooking could damage the plasma membrane.
• Could denature the proteins.
• A lot of pigment is released during cooking so there would be less pigment present in the tissue.
You used a water bath in this investigation. Explain why a decrease in temperature would affect the results.
• By decreasing the temperature the kinetic energy of the particles would also be decreased.
• This means for a lower rate of diffusion.
2 students carried out the same investigation as you did. They worked in the same practical session and followed the same procedure. They worked accurately but found their results were different. Suggest one reason for this.
Variation in beetroot.
Should you start from the origin in your graph if you have not collected data for that?
No as curves drawn on graphs gould not extend beyond data collected.
How should you check if you think you have an anomaly on your graph?
• Repeat that specific part of the experiment.
• Check to see if results are concordant.
Why is it necessary to keep a suitable control in this experiment?
• To show alcohol in causing the leaking of the pigment.
• To compare with the effects of alcohol.
