Which surface change helps explain why nanoparticles can react differently from a large lump of the same substance?

• The fraction of atoms at the surface decreases.
• The fraction of atoms at the surface increases.
• The fraction of atoms at the surface is fixed.

Which range gives the full typical size band used to define nanoparticles?

• 1 to 100 nanometres
• 1 to 10 nanometres
• 1 to 1000 nanometres

Safety data for a bulk substance always gives enough information to judge every nanoparticle product made from it.

A 2 cm cube is cut into eight separate 1 cm cubes. Exposed area doubles from 24 to 48 cm². In a model where reaction rate per cm² stays constant, what happens to total reaction rate?

• It becomes half the original rate.
• It remains at the original rate.
• It becomes twice the original rate.

A 3 cm cube is cut into 27 separate 1 cm cubes. Total surface area rises from 54 cm² to 162 cm². Total volume remains 27 cm³. What is the new surface area to volume ratio, in per cm?

A cube has surface area 24 cm² and surface area to volume ratio 3 per cm. What is its volume, in cm³?

A maker changes a nanoparticle skin lotion into a spray that releases inhalable particles. The material and coating stay the same. Which safety plan best addresses the change?

• Use the lotion's skin tests to judge the spray's lung effects.
• Repeat the skin tests at the same dose to cover inhalation.
• Assess inhalation exposure as well as relevant existing data.

A sunscreen maker wants UV protection with less visible whitening. Why might titanium dioxide nanoparticles suit this use better than larger particles of the same material?

• They reduce UV exposure while scattering less visible light.
• They reduce UV exposure by scattering more visible light.
• They reduce visible light while letting more UV reach skin.