Revision notes · Bonding, structure, and the properties of matter
Bulk and surface properties of matter including nanoparticles
Sizes of particles and their properties4.2.4.1
Definition: A nanoparticle is a particle with a diameter between 1 and 100 nanometres, consisting of a few hundred atoms.
Nanoparticles are extremely tiny particles that behave differently from bulk materials because of their very high surface area to volume ratio.
| Type | Diameter |
|---|---|
| Nanoparticles | 1–100 nm (1 × 10⁻⁹ m to 1 × 10⁻⁷ m) |
| Fine particles | 100–2,500 nm |
| Coarse particles (dust) | 2,500–10,000 nm |
- •As the side length of a cube decreases by a factor of 10, its surface area to volume ratio increases by a factor of 10.
- •Their huge surface area to volume ratio means much smaller quantities of nanoparticles are needed to achieve the same effect as bulk materials.
⚠️ Common mistake: Thinking nanoparticles are individual atoms or molecules, rather than structures made of a few hundred atoms.
🧠 Remember: Shrink the side length by 10, and the surface area to volume ratio jumps by 10.
Uses of nanoparticles4.2.4.2
Definition: Nanoscience is the study and application of structures that are between 1 and 100 nanometres in size.
The unique properties of nanoparticles give them many practical applications in medicine, consumer products, and industrial catalysts.
| Use | How |
|---|---|
| Catalysts | Massive surface area provides many active sites for reactions |
| Sunscreens | Titanium dioxide nanoparticles give UV protection without a visible white residue |
| Antibacterial products | Silver nanoparticles in deodorants, wound dressings, clothing |
| Medicine | Cage-like nanoparticles deliver drugs directly to target cells (e.g. tumours) |
- •The risks of nanoparticles are not fully understood, as they could enter human body cells or cause long-term environmental damage.
⚠️ Common mistake: Assuming nanoparticles are completely safe because they are used in everyday products; their long-term health and environmental effects are still unknown.
🧠 Remember: Think MEDIC: Medicine, Electronics, Deodorants, Industrial catalysts, Cosmetics/sunscreens.
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