Biology Unit 1 AOS3 Flashcards
Accuracy
How close is your result to the actual result?
Precision
Ability to get the same result multiple times
Validity
Does your experiment test what you have intended it to? Could results be affected by anything else?
Systematic Errors
Occur consistently and affect the accuracy of the data.
Eg of Systematic Error (3)
- faulty calibration of measuring instruments (and uncalibrated instruments) that consistently give the same inaccurate reading for the same value being measured
- poorly maintained instruments
faulty - reading of instruments by the user
(for example, ‘parallax error’).
Random Errors (2)
- Affect the precision of a measurement and are always present in measurements.
- These types of errors are unpredictable variations in the measurement process and result in a spread of readings or data points.
Eg Random Errors (3)
- Variations in estimating a quantity that lies between the graduations (lines) on a measuring instrument
- The inability to read an instrument because the reading fluctuates during the measurement
- Unpredictable changes to conditions such as temperature or weather during an experiment.
How to reduce random errors? (4)
- Take multiple measurements and calculate the average, use more precise instruments, and increase the sample size.
How to reduce systematic errors?
- Careful experimental design
- Instrument calibration, and standardised procedures
What is meant by a controlled experiment?
- A scientific test done under controlled conditions, meaning that just one (or a few) factors are changed at a time, while all others are kept constant.
What are the main steps in the scientific method?
- Formulate a question.
- Research the question.
- Form a hypothesis.
- Design a controlled experiment which identifies sources of experimental errors
- Analyse data.
- Draw Conclusions.
- Communicate results.
Qualitative
- information that describes qualities, characteristics, or attributes, rather than being numerical or measurable
Quantitative
- information expressed numerically, such as statistics, percentages, or measurements
Why must a control be included in an experiment?
provide a baseline for comparison of the dependent variable in the experiment.
How was absorbance used in our investigation to determine membrane permeability?
Absorbance was used to measure how much pigment leaked from the beetroot cells. The more pigment in the water, the more light was absorbed. At low temperatures, the cell membrane stayed strong, so little pigment leaked out. This meant low absorbance. At higher temperatures, the membrane broke down, letting more pigment escape. This led to higher absorbance.
How does a colorimeter work?
A colorimeter works by measuring how much light passes through a liquid sample. It shines light of a specific wavelength through the sample and detects how much light is absorbed by the solution.
What errors did you encounter in your investigation?
One major error was the large difference in absorbance values for the 60°C trial between the first (0.656) and second (2.317) readings. This was unusual because the highest temperature (80°C) had lower and more consistent absorbance values (0.689 and 0.795). Possible causes of this error include:
- The colorimeter may not have been properly calibrated
- The water bath may not have maintained a stable temperature, causing uneven pigment release.
How did you try to minimise the errors?
Calibrated the Colorimeter – Used distilled water to reset the colorimeter before each measurement.
Shook the Test Tubes – Mixed the solutions before measuring to ensure even distribution of pigment.
Standardized Beetroot Pieces – Tried to use beetroot pieces of the same size and shape.
Controlled Temperature – Ensured the water bath maintained a stable temperature.
How would you improve your method?
Take More Trials – Conduct at least three trials to get a more reliable average.
Better Temperature Control
