# Titanium dioxide exists as both bulk material and as nanoparticles. Explain why titanium dioxide nanoparticles are more effective as a catalyst than the same mass of bulk titanium dioxide.

> Edexcel GCSE Chemistry (1CH0) — 9.2 Bulk and surface properties of matter, including nanoparticles (Chem only) · Explain · 4 marks

> Titanium dioxide is a white solid used as a pigment in paints. Scientists are investigating its use as a catalyst in industrial reactions. Nanoparticles of titanium dioxide have a diameter of around 20 nm.

## Mark scheme (4 marks)

1. Nanoparticles have a much larger surface area to volume ratio than bulk titanium dioxide
2. Because more atoms/particles are exposed on the surface (for the same mass)
3. More active sites are available for reactant molecules to interact with
4. Therefore the rate of the catalysed reaction is increased / the catalyst works more efficiently

## Key terms

- [nanoparticles](https://www.gradenine.co.uk/glossary/nanoparticles)
- [catalyst](https://www.gradenine.co.uk/glossary/catalyst)
- [bulk](https://www.gradenine.co.uk/glossary/bulk)

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/titanium-dioxide-exists-as-both-bulk-433ce241) · Published by Druglandscape Ltd.