2.4.1Atoms, Elements and Compounds
Nanoparticles — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 5 parts Lesson 8 of 26 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Size and Classification
Particles are classified by diameter, and nanoparticles sit at the smallest end of the scale.
Nanoscience
- Nanoscience Structures between 1 and 100 nm in size are studied in nanoscience, and nanoparticles usually contain only a few hundred atoms.
Nanoparticles
- Nanoparticles Nanoparticles have diameters between 1 and 100 nm, much smaller than fine particles.
Fine particles
- Fine particles Particles with diameters between 100 and 2500 nm are classed as fine particles.
Coarse particles
- Coarse particles Larger particles, such as dust, are classed as coarse particles, also called particulate matter.
Section 2 of 5Surface Area to Volume Ratio
The key idea is that shrinking a particle increases its surface area compared with its volume.
1
Reducing the side length of a cube by a factor of 10 increases its surface area to volume ratio by a factor of 10.
2
A smaller particle therefore has a larger proportion of its atoms at the surface, where reactions take place.
3
Because of this, nanoparticles can show properties that are different from the same material in bulk form.
4
Fewer nanoparticles are often needed to achieve the same effect, because more of the material is exposed to its surroundings.
Section 3 of 5Applications of Nanoparticles
Applications of Nanoparticles
Catalysis
- Catalysis Nanoparticles provide a large surface for reactions, which makes them effective catalysts.
Sunscreen
- Sunscreen Nanoparticle titanium dioxide blocks ultraviolet light while remaining transparent on the skin.
Medicine
- Medicine Fullerene-based carriers can be absorbed by the body and deliver drugs to target areas.
Medical textiles
- Medical textiles Silver nanoparticles on fabrics give antibacterial properties while the material stays flexible.
| Material | Bulk form use | Nanoparticle form use |
|---|---|---|
| Titanium dioxide | White pigment in paint | Transparent UV-blocking sunscreen |
| Silver | Solid metal objects | Antibacterial coating on surgical masks |
Section 4 of 5Worked Example
Question
- A cube of side 1 cm is cut into small cubes of side 0.1 cm.
- Compare the surface area to volume ratio of the small cube with that of the large cube.
- Large cubesurface area = 6 × 1² = 6 cm², volume = 1³ = 1 cm³, so the ratio is 6 cm⁻¹.
- Small cubesurface area = 6 × 0.1² = 0.06 cm², volume = 0.1³ = 0.001 cm³, so the ratio is 0.06 ÷ 0.001 = 60 cm⁻¹.
- Compare the ratios60 ÷ 6 = 10.
Answer The small cube has a surface area to volume ratio 10 times larger, which matches the rule that a factor of 10 reduction in side length gives a factor of 10 increase.
Section 5 of 5Exam Checklist & Tips
2.4.1 – Key Points for the Exam
- Nanoparticle A particle between 1 and 100 nanometres in diameter.
- Surface area to volume ratio
- The surface area of an object divided by its volume;
- it increases as particles get smaller.
- The surface area of an object divided by its volume;
- Bulk material A normal-sized sample of a material, which shows its ordinary properties.
- Nanoscience The study and application of structures between 1 and 100 nanometres in size.
Common Mistakes
- Stating that nanoparticles are simply smaller atoms; they usually contain a few hundred atoms.
- Confusing the surface area with the surface area to volume ratio.
- Claiming nanoparticles always behave differently, rather than explaining the difference by the high surface area.
- Using the wrong conversion1 nm is 10⁻⁹ m, so 100 nm is 10⁻⁷ m.
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