Starch is a common carbohydrate found in leaf litter. Scientists investigated the rate of starch breakdown by saprobiontic microorganisms in soil samples at two different pH treatments: pH 4.5\text{pH } 4.5pH 4.5 and pH 6.5\text{pH } 6.5pH 6.5.
They measured the concentration of starch in soil samples over 12 days. Each sample started with the same initial concentration of starch and had the exact same dry mass of soil. Their results are shown in the graph below:
Suggest why, in this investigation, the scientists expressed the concentration of starch in units of μg g−1\mu\text{g g}^{-1}μg g−1.
Calculate the difference in the rate of starch breakdown per day between day 0 and day 4 at pH 4.5\text{pH } 4.5pH 4.5 and pH 6.5\text{pH } 6.5pH 6.5. Show your working and state the units for your answer.
