A student group designed four different scientific experiments but realized that each procedure contained a critical confounding variable or source of error that could compromise the validity of the results.
Match each experimental procedure on the left with its primary confounding variable or source of error on the right.
- To measure amylase activity at different pH levels, a student mixes amylase dissolved in pH buffers with a starch substrate dissolved in unbuffered distilled water.Dilution of the buffer system by the unbuffered substrate solution, shifting the reaction mixture's actual pH away from the targeted buffer levels.
- To determine the specific heat capacity of a metal alloy, a heated sample is transferred from a boiling water bath at to a calorimeter containing water at using metal tongs kept at .An uncontrolled thermal gradient where the transfer tool acts as a heat sink, lowering the initial temperature of the sample before calorimetric measurement begins.
- To compare photosynthetic rates at different light intensities, glass chambers containing plants are placed at varying distances from a high-intensity incandescent light source without temperature regulation.Confounding of the independent variable with thermal energy, as changing the distance to the light source simultaneously alters both light intensity and chamber temperature.
- To measure diurnal ground-level ozone concentrations, a UV absorption sensor detecting attenuation of light is placed next to a busy highway intersection with fluctuating traffic.Fluctuations in light-scattering particulates and co-pollutants that absorb the same wavelength, leading to an overestimation of the target gas concentration during peak traffic hours.
Answer
Amylase activity matches with buffer dilution; Specific heat capacity matches with thermal gradient transfer tool; Photosynthesis rate matches with thermal energy from the light source; Ozone concentration matches with UV-absorbing particulate and gas interference.
The correct pairings successfully match each experimental flaw to its specific confounding factor or error source. Mixing unbuffered substrate with buffered enzyme shifts the target pH. Using room-temperature tongs transfers heat away from the hot metal alloy. Incandescent light sources introduce heat along with light, altering temperatures at different distances. Highway traffic introduces particulate matter and gases that absorb UV light, interfering with ozone detection.
Step-by-Step Solution
Key Concept
Identifying confounding variables and uncontrolled factors in experimental procedures
Estimated Time:3m 0s