The paper clip is more dense than water but can rest on the surface of the water because of the water's surface tension. Evidence of water's surface tension can be seen where the water strider's legs ...

The formula for the volume and surface area of a sphere will be given to you in the exam, so you will not need to memorise these. \(\text{The volume of a sphere} ~=~ \frac {4}{3} \times \pi \times ...

Make sure you answer questions in terms of surface area to volume ratio, rather than just surface area. This is because the surface area also depends on the mass of solid reactant used.