A student investigated the effect of temperature on the decay of fresh milk by measuring its pH over a period of 5 days.
The student followed this method:
Table 1 shows the measurements at 18∘C18^\circ\text{C}18∘C:
\begin{array}{|c|c|c|c|c|c|c|} \hline \text{Time (days)} & 0 & 1 & 2 & 3 & 4 & 5 \\\ \hline \text{pH} & 6.8 & 6.8 & 6.5 & 5.6 & 4.8 & 4.5 \\\ \hline \end{array}Answer the following questions:
How could the student keep the milk at a constant temperature of 18∘C18^\circ\text{C}18∘C for 5 days?
Give one variable, other than temperature, that the student should keep constant.
In a graph of these results, with pH on the y-axis and Time on the x-axis, describe how the curve representing the milk at 24∘C24^\circ\text{C}24∘C would compare to the curve for 18∘C18^\circ\text{C}18∘C.
40 exam-style questions on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only). Each one has a worked solution and a mark scheme showing where the marks go.