Ace the IGCSE Chemistry Challenge 2025 – Ignite Your Science Success!

One mole of a substance represents a specific quantity defined as Avogadro's number, which is approximately \(6.02 \times 10^{23}\) entities, such as atoms, molecules, or ions. When referring to carbon-12, one mole corresponds to the number of atoms found in exactly 12 grams of carbon-12. This definition is pivotal in chemistry, as it allows scientists to relate the mass of a substance to the number of particles it contains, facilitating calculations in stoichiometry and enabling the use of the mole concept in various chemical equations and reactions.

The other options do not accurately represent the definition of a mole. For instance, while a specific volume of a gas can be determined at certain conditions (like standard temperature and pressure), this does not define what a mole is. Similarly, a percentage of a substance or the weight of a liquid do not correspond to the concept of a mole in terms of particle quantity. Thus, the answer regarding the number of atoms in 12 grams of carbon-12 is the correct interpretation of what one mole represents in the context of chemistry.