O File C:/Users/mxham/Downloads/OCR_ExamB... A student used cubes of agar jelly containing universal indicator, which changes colour at different pH. • Five different sizes of cubes were cut from a...

Extracted text: O File C:/Users/mxham/Downloads/OCR_ExamB... A student used cubes of agar jelly containing universal indicator, which changes colour at different pH. • Five different sizes of cubes were cut from a larger block using a scalpel. • Cubes were placed in a beaker containing hydrochloric acid (enough to cover the cubes) and a stopwatch was started. • After 2 minutes the cubes were removed, rinsed with distilled water and blotted dry. • Acid absorbed at the outside continued diffusing towards the centre of the blocks. • The time taken for the blocks to turn entirely red was recorded. The results are shown in Table 22.1 on the insert. Length of one side of Surface Time taken to turn red (min) area to Cube agar cube (mm) volume Test 1 Test 2 Test 3 Mean ratio 1.20 6.4 2.9 5.4 4.9 B 10 0.60 14.8 15.5 14.6 15.0 20 0.30 30.6 28.3 27.4 28.8 30 0.20 44.1 42.2 43.0 43.1 E 40 0.15 58.7 60.1 57.4 58.7 Table 22.1 Whal was llie role ul the universal indicalur m this experiment? -------------------


Extracted text: A student used cubes of agar jelly containing universal indicator, which changes colour at different pH. • Five different sizes of cubes were cut from a larger block using a scalpel. • Cubes were placed in a beaker containing hydrochloric acid (enough to cover the cubes) and a stopwatch was started, • After 2 minutes the cubes were removed, rinsed with distilled water and blotted dry. • Acid absorbed at the outside continued diffusing towards the centre of the blocks. • The time taken for the blocks to turn entirely red was recorded. The results are shown in Table 22.1 on the insert Length of one side of Surface Time taken to turn red (min) Cube area to agar cube (mm) volume Test 1 Test 2 Test 3 Mean ratio 1.20 6.4 2.9 5.4 4.9 B 10 0.60 14.8 15.5 14.6 15.0 20 0.30 30.6 28.3 27.4 28.8 D 30 0.20 44.1 42.2 43.0 43.1 40 0.15 58.7 60.1 57.4 58.7 Tablo 111