The three states of matter: recognise that atoms themselves do not have the bulk properties of materials

The idea

Bulk properties are the large-scale behaviours we observe, such as melting point, boiling point, density, conductivity and solubility. They emerge from how enormous numbers of atoms or molecules are arranged and how they interact, not from a single atom. One isolated atom has no melting point, no boiling point and no fixed density because these ideas only make sense for a collection of particles. For example, a single copper atom cannot conduct electricity through a wire, yet a copper wire does because delocalised electrons move through the whole lattice. Similarly, one water molecule does not boil at 100 °C; boiling describes molecules escaping from a bulk liquid. When you explain a material's properties, refer to the particles, their arrangement, and the forces or bonds between them, rather than saying the atoms themselves are hard, shiny or dense.

What earns the marks

• State that bulk properties belong to a material made of many atoms, not to one atom on its own.
• Give a named bulk property such as melting point, boiling point, density, conductivity or solubility.
• Explain that the property depends on the arrangement of particles and the forces or bonds between them.
• Use a specific example, such as copper conducting because of delocalised electrons throughout the lattice, or water boiling because many molecules escape together.
• Avoid describing an individual atom as having a property such as shiny, hard, dense or a fixed melting point.

Common mistakes and how to put them right

• Saying a single atom is hard or shiny.

  Put it right by explaining that hardness and shininess are bulk properties arising from many atoms and their bonding.

• Claiming one atom has a melting point.

  Put it right by stating that melting point describes a bulk sample changing state, not an isolated particle.

• Confusing the properties of an element with the properties of one atom.

  Put it right by linking the material's behaviour to the particle arrangement and intermolecular or metallic bonding.

Exam tips

• Read the question carefully: if it asks about a material or a sample, answer in terms of many particles, not one atom.
• When asked to explain a property, name the property, then link it to particle arrangement and the forces or bonds present.
• Use a quick contrast in your answer, such as 'one copper atom cannot conduct, but a copper wire can because delocalised electrons move through the lattice'.