Biology 0610 · IGCSE · Diffusion

Diffusion — practice question

A student explored how surface area influenced the rate of diffusion. The student began with four agar cubes, each with a volume of $1\text{ cm}^3$. The agar cubes were stained with a red indicator. When the red indicator was exposed to acid, it changed to yellow. To raise the surface area, the student cut the cubes into different numbers of blocks. As shown in Fig. 3.1, the blocks were then put into acid. For each test-tube, the student measured how long it took for every agar block to turn yellow. The investigation was carried out twice more, and a mean was then calculated.
(a(i))[2]

Calculate the mean time taken for all the blocks in test-tube C to turn yellow. Give your answer to the nearest whole number.

(a(ii))[1]

Using the results in Table 3.1, describe the effect of surface area on diffusion.

(a(iii))[1]

State one factor, apart from surface area, that could influence diffusion in this investigation.

(a(iv))[3]

Complete the sentences to describe how the acid particles diffuse to cause the colour change. The acid particles move from the acid solution into the [BLANK], down a [BLANK] gradient. The energy for this process comes from the [BLANK] energy of random movement of the acid particles.

(b)[1]

Describe one way that osmosis differs from other types of diffusion.

(c(i))[2]

Circle the two substances needed for aerobic respiration in humans. carbon dioxide glucose glycogen oxygen protein urea water

(c(ii))[1]

State the site in cells where aerobic respiration occurs.

(c(iii))[1]

State the name of the structure through which substances pass to enter any cell.

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