---
title: "Silicones and their uses"
subject: "Engineering Chemistry"
chapter: 4
key: "semester_2/engineering_chemistry:silicones-uses"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/silicones-uses
site: BCT Engineering
---

# Silicones and their uses

Engineering Chemistry · Chapter 4: Engineering Polymers

- Asked in: 2067 Mangsir, 2 marks
- Video: [Why Silicone is a Miracle Material | Chemistry](https://www.youtube.com/watch?v=x3xkFyLm6lI) — Zahl Azizi
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/silicones-uses
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-4

## Question

What are silicones? Give any two uses of silicones.

## Short answer

Silicones are organosilicon polymers with a –Si–O– backbone and organic side groups, heat-stable and water-repellent. They are used as lubricants across wide temperature ranges, and for electrical insulation, sealants and coatings.

## Answer

**Silicones** are inorganic–organic polymers having a backbone of alternating Si and O atoms (–Si–O–Si–) with organic groups, usually methyl, attached to silicon; general formula [R₂SiO]ₙ. They are heat stable, water repellent and chemically inert.

**Two uses:**
1. Silicone oils and greases as lubricants over a wide temperature range.
2. Silicone rubber and resin for electrical insulation, sealants and medical implants (also water-repellent coatings).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the backbone of silicones?
   A. Alternating P and N atoms
   B. Alternating Si and O atoms with organic groups on Si
   C. C–C chain
   D. Alternating S and N atoms
   Answer: B. Silicones have general formula [R2SiO]n. (Key point: Backbone)

2. Which properties characterise silicones?
   A. Flammable and water soluble
   B. Brittle and conducting
   C. Heat stable, water repellent and chemically inert
   D. Biodegradable and reactive
   Answer: C. Strong Si–O bonds give stability and inertness. (Key point: Properties)

3. Which is a use of silicone oils and greases?
   A. Fertilisers
   B. Explosives
   C. Metal ores
   D. Lubricants over a wide temperature range
   Answer: D. Silicone oils lubricate across wide temperatures; rubber and resin serve as insulation and sealants. (Key point: Uses)

## Related in Engineering Chemistry

- [Types and uses of silicones](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Asilicones-types-uses) — Engineering Chemistry, chapter 4
- [Inorganic polymer; network polymer of sulphur; silicones](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ainorganic-polymer-sulphur) — Engineering Chemistry, chapter 4