The NDA CDS 1 2026 examination tests candidates on conceptual clarity and application-based understanding of General Science topics, including Chemistry. In Chemistry, questions are generally fact-based, conceptual, and MCQ-oriented, covering fundamental themes from Class 9–12 NCERT. Topics like Polymers and Cement Preparation are commonly included because they deal with practical, real-life applications of chemical principles.
Introduction
In this class, we explore two important industrial chemistry topics—Polymers and Cement Preparation. Polymers play a critical role in daily life, from plastics to fibres. Cement, on the other hand, is a key building material that drives infrastructure and construction. Understanding their basic chemistry helps in answering MCQs effectively and linking classroom concepts to real-world applications.
Topic 1: Polymers
Definition
A polymer is a large molecule made up of repeating structural units called monomers.
Subtopics
1. Classification of Polymers
- On the basis of source:
– Natural polymers (e.g., cellulose, proteins)
– Synthetic polymers (e.g., nylon, polythene) - On the basis of structure:
– Linear polymers
– Branched-chain polymers
– Cross-linked polymers - On the basis of polymerization:
– Addition polymers (e.g., polythene, PVC)
– Condensation polymers (e.g., nylon-6,6; bakelite)
2. Polymerization Processes
- Addition polymerization
- Condensation polymerization
- Role of initiators and catalysts
3. Important Polymers for MCQs
- Polythene (LDPE, HDPE)
- PVC (Polyvinyl chloride)
- Teflon (PTFE)
- Bakelite
- Nylon-6 and Nylon-6,6
- Rubber (natural & vulcanized rubber)
4. Applications of Polymers
- Packaging materials
- Fibres and textiles
- Insulation
- Tools, adhesives, household items
Topic 2: Preparation of Cement
Definition
Cement is a finely ground mixture of calcareous and argillaceous materials used as a binding material in construction.
Subtopics
1. Raw Materials
- Limestone (CaCO₃) – primary source of calcium
- Clay – provides silica, alumina, and iron oxide
2. Manufacturing Process
Two main methods:
- Dry Process (commonly used)
- Wet Process
Steps in Cement Manufacture:
- Crushing and grinding of raw materials
- Mixing in a definite proportion
- Heating in a rotary kiln at ~1500°C
– Formation of clinker - Cooling and grinding of clinker
- Addition of gypsum (CaSO₄·2H₂O) to regulate setting time
- Final cement packing
3. Types of Cement
- Ordinary Portland Cement (OPC)
- Rapid Hardening Cement
- Portland Pozzolana Cement (PPC)
4. Setting and Hardening
- Setting: initial stiffening due to hydration
- Hardening: crystallization and formation of binding compounds (CSH gel)
5. Uses of Cement
- Construction (bridges, dams, buildings)
- Roads and pavements
- Plastering and masonry
Conclusion
Polymers and cement are two pillars of modern material science. Polymers provide flexibility and versatility, while cement forms the backbone of construction. For NDA CDS 1 2026, understanding definitions, processes, classifications, and key examples is essential for solving MCQs quickly and accurately. Mastery of these topics strengthens both exam preparation and real-world scientific awareness.
