# 4.2.4.1

4.2.4.1 Sizes of particles and their properties

## Content

• Nanoscience refers to structures that are 1–100 nm in size, of the order of a few hundred atoms. Nanoparticles, are smaller than fine particles (PM2.5), which have diameters between 100 and 2500 nm (1 x 10-7 m and 2.5 x 10-6 m). Coarse particles (PM10) have diameters between 1 x 10-5 m and 2.5 x 10-6 m. Coarse particles are often referred to as dust.

As the side of cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10.

Nanoparticles may have properties different from those for the same materials in bulk because of their high surface area to volume ratio. It may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes.

Students should be able to compare ‘nano’ dimensions to typical dimensions of atoms and molecules.

WS 1.2 Use a variety of models such as representational, spatial, descriptive, computational and mathematical to solve problems, make predictions and to develop scientific explanations and understanding of familiar and unfamiliar facts.

WS 1.4 Explain everyday and technological applications of science; evaluate associated personal, social, economic and environmental implications; and make decisions based on the evaluation of evidence and arguments.

WS 4.1 Use scientific vocabulary, terminology and definitions.

WS 4.2Recognise the importance of scientific quantities and understand how they are determined.

WS 4.3 Use SI units (eg kg, g, mg; km, m, mm; kJ, J) and IUPAC chemical nomenclature unless inappropriate.

WS 4.4 Use prefixes and powers of ten for orders of magnitude (eg tera, giga, mega, kilo, centi, milli, micro and nano).

WS 4.5 Interconvert units.

MS 2h Make order of magnitude calculations

MS 5c Calculate areas of triangles and rectangles, surface areas and volumes of cubes

MS 1b - Recognise and use expressions in standard form

MS 1c Use ratios, fractions and percentages

MS 1d Make estimates of the results of simple calculations