Practical Investigation Reference¶
This page brings together the practical patterns that recur across the course so common methods, measurements and evaluation points can be revised in one place.
Practical Focus¶
- Gather the practical investigations that are distributed across the course.
- Track common method choices, variables, controls, measurements, graphing habits and evaluation patterns.
- Show how practical skills recur across different topics instead of sitting in a separate unit.
Investigation Map¶
| Topic page | Specification practicals | Main investigation focus | Useful measurements or observations |
|---|---|---|---|
| 2c Biological Molecules | 2.9, 2.12, 2.14B |
food tests plus enzyme activity against temperature and pH | precipitate or colour change, time to end-point, and controlled hot water-bath or buffer conditions |
| 2d Movement of Substances into and out of Cells | 2.17 |
diffusion and osmosis in living and non-living systems | mass change, concentration, time, consistent blotting and sample size |
| 2e Nutrition | 2.23, 2.33B |
photosynthesis requirements and energy content of food | oxygen bubbles per minute or oxygen release, lamp distance or relative light intensity, starch test results, temperature rise and mass of food burnt |
| 2f Respiration | 2.39 |
respiring organisms releasing carbon dioxide and heat | indicator change, temperature change, bubble count or time under controlled conditions, and capillary-fluid movement in a sealed respirometer model |
| 2g Gas Exchange | 2.45B, 2.50 |
net gas exchange in plants and breathing in humans | indicator colour, breathing rate, carbon dioxide output and effect of exercise |
| 2h Transport | 2.58B |
environmental factors affecting transpiration | distance moved by bubble, time, and controlled humidity, wind, light or temperature; remember a standard potometer measures water uptake rather than transpiration directly |
| 3a Reproduction | 3.5 |
conditions needed for seed germination | germination success across controlled water, oxygen and temperature conditions |
| 4a The Organism in the Environment | 4.2, 4.4B |
population size, organism distribution and biodiversity using quadrats | counts, percentage cover, sample number and random or transect placement |
Recurring Method Patterns¶
- In the Elodea lamp-distance practical, move the lamp and measure the oxygen output per unit time, usually by counting bubbles for a set time. You can then compare the results against lamp distance or against a relative light-intensity value. Open the full interactive model.
- In a sealed respirometer model, capillary fluid rises only because carbon dioxide is being absorbed, so the remaining decrease in gas volume reflects oxygen uptake. Open the full interactive model.
- In a leaf starch test, boil the leaf in water, heat it in ethanol in a hot water bath to remove chlorophyll, rinse it, then add iodine on a white tile. A blue-black result shows starch is present, and ethanol must be kept away from naked flames because it is flammable.
- Keep one independent variable changing at a time and state the dependent variable clearly before collecting data.
- Standardise sample size, starting mass, volume, time and temperature whenever those factors could change the outcome.
- Use repeats and averages to improve reliability, especially in ecology sampling and rate-based practicals.
- Distinguish qualitative observations such as colour change from quantitative measurements such as mass, bubble count or temperature rise.
- When evaluating a method, look first for uncontrolled variables, inconsistent measurements and weak repeat structure before suggesting improvements.