Cambridge IGCSE Chemistry · Syllabus 0620 · Chemical Reactions
Surface Area
What is Surface Area?
The total area of a solid that is exposed to the surrounding reactant. Breaking a fixed mass of solid into smaller pieces exposes surfaces that were previously buried inside, so the surface area rises while the mass stays the same, and the reaction rate rises with it.
This definition is part of the Chemical Reactions chapter in Cambridge IGCSE Chemistry.
Common mistakes with Surface Area
- 5. “Grinding the solid increases its concentration.” Core 6.2.1 Why temptingBoth changes make a reaction faster, so the words get swapped. RepairSolids do not have a concentration; concentration is defined for a solute in a solution. Grinding increases the surface area, exposing more particles. TransferState what is unchanged when a lump is ground to powder. The mass, the number of particles present and the final amount of product.
Examiner tips on Surface Area
- Say “surface area”, never “concentration”. A solid does not have a concentration; concentration is defined for a solute in a solution. “Grinding the solid increases its concentration” names the wrong quantity, so the sentence is wrong however sound the reasoning around it is. In the same way, a pressure change only affects the rate if at least one reactant is a gas — check for a \((\mathrm{g})\) state symbol before you write anything about pressure.