The difference in the rates of reaction of large lumps and of small lumps of a solid reactant, such as magnesium, depends on the surface area to volume ratio of the lumps.
Figure 1 shows a small cube of magnesium reactant.
a.[3]
Calculate the surface area to volume ratio of the cube in Figure 1. Give your answer as the simplest whole number ratio in the form surface area:volume\text{surface area} : \text{volume}surface area:volume.
b.[2]
A larger cube of magnesium has side lengths of 1.2 cm1.2\text{ cm}1.2 cm.
Describe how the surface area to volume ratio of this larger cube differs from that of the cube shown in Figure 1.