NDA Chemistry · Industrial and Applied Chemistry
Cement, Glass and Building Materials
What glass and Portland cement are actually made of — their raw materials, the chemical compounds inside set cement, and the property statements (glass is a supercooled liquid; pyrex beats soda glass) the bank loves to test.
Why this matters
Six PYQs, mostly EASY/MODERATE. The bank asks the raw materials of glass or cement, the compounds present in set cement, or a 'which statement about glass is NOT correct' trap. Two reliable facts win most marks: glass is an amorphous (non-crystalline) supercooled liquid, and Portland cement is made from lime, silica and alumina.
Concept 1 of 2: Glass — nature and raw materials
Definition
The glass facts the bank tests:
- Glass is an amorphous (non-crystalline) solid — often described as a supercooled liquid; it has no definite melting point.
- Raw materials: silica sand (SiO₂) — the source of silica, soda ash (Na₂CO₃), limestone (CaCO₃), and borax for borosilicate glass.
- Gypsum is NOT a glass raw material (it belongs to cement/plaster).
- Pyrex (borosilicate) glass contains boron oxide, making it harder and more heat-resistant than ordinary soda glass.
| Aspect | Glass fact | Note |
|---|---|---|
| Physical nature | Amorphous, non-crystalline solid | Supercooled liquid; no definite melting point Glass is a non-crystalline amorphous solid — a supercooled liquid. |
| Source of silica | Sand (SiO₂) | The silica-providing raw material Sand is the source of silica in glass-making. |
| Other raw materials | Soda ash, limestone, borax | Borax → borosilicate (pyrex) |
| NOT a glass material | Gypsum (CaSO₄·2H₂O) | Belongs to cement/plaster, not glass Gypsum is the trap option — it is NOT used in making glass. |
| Pyrex vs soda glass | Pyrex is harder | Pyrex has boron oxide; heat-resistant 'Soda glass is harder than pyrex' is FALSE — pyrex (borosilicate) is the harder, more heat-resistant one. |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Industrial and Applied Chemistry · Cement, Glass and Building Materials
Pyrex is harder than soda glass
Gypsum is the glass trap
Concept 2 of 2: Portland cement — raw materials and compounds
Definition
The cement facts the bank tests:
- Essential raw materials / constituents: lime (CaO), silica (SiO₂) and alumina (Al₂O₃) (plus a little iron oxide).
- Compounds present in set Portland cement:
- 3CaO·SiO₂ (tricalcium silicate, alite)
- 2CaO·SiO₂ (dicalcium silicate, belite)
- 3CaO·Al₂O₃ (tricalcium aluminate)
- 4CaO·Al₂O₃·Fe₂O₃ (tetracalcium aluminoferrite)
- 4CaO·SiO₂ is NOT a cement compound — the silicates are only the 3:1 and 2:1 ratios.
- Gypsum is added in a small amount to regulate the setting time.
| Aspect | Cement fact | Note |
|---|---|---|
| Raw materials | Lime, silica, alumina | + a little iron oxide Essential constituents of Portland cement: silica, alumina, lime. |
| Alite | 3CaO·SiO₂ | Tricalcium silicate |
| Belite | 2CaO·SiO₂ | Dicalcium silicate |
| Aluminate | 3CaO·Al₂O₃ | Tricalcium aluminate |
| NOT in cement | 4CaO·SiO₂ | No such silicate; only 3:1 and 2:1 4CaO·SiO₂ is the trap — it is NOT a standard cement compound. |
| Setting regulator | Gypsum (small amount) | Slows the setting time |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Industrial and Applied Chemistry · Cement, Glass and Building Materials
4CaO·SiO₂ does not exist in cement
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Glass — nature and raw materials5 rows
| Aspect | Glass fact | Note |
|---|---|---|
| Physical nature | Amorphous, non-crystalline solid | Supercooled liquid; no definite melting point Glass is a non-crystalline amorphous solid — a supercooled liquid. |
| Source of silica | Sand (SiO₂) | The silica-providing raw material Sand is the source of silica in glass-making. |
| Other raw materials | Soda ash, limestone, borax | Borax → borosilicate (pyrex) |
| NOT a glass material | Gypsum (CaSO₄·2H₂O) | Belongs to cement/plaster, not glass Gypsum is the trap option — it is NOT used in making glass. |
| Pyrex vs soda glass | Pyrex is harder | Pyrex has boron oxide; heat-resistant 'Soda glass is harder than pyrex' is FALSE — pyrex (borosilicate) is the harder, more heat-resistant one. |
Portland cement — raw materials and compounds6 rows
| Aspect | Cement fact | Note |
|---|---|---|
| Raw materials | Lime, silica, alumina | + a little iron oxide Essential constituents of Portland cement: silica, alumina, lime. |
| Alite | 3CaO·SiO₂ | Tricalcium silicate |
| Belite | 2CaO·SiO₂ | Dicalcium silicate |
| Aluminate | 3CaO·Al₂O₃ | Tricalcium aluminate |
| NOT in cement | 4CaO·SiO₂ | No such silicate; only 3:1 and 2:1 4CaO·SiO₂ is the trap — it is NOT a standard cement compound. |
| Setting regulator | Gypsum (small amount) | Slows the setting time |
Watch out for (3)
- Pyrex is harder than soda glass→ Glass — nature and raw materials
- Gypsum is the glass trap→ Glass — nature and raw materials
- 4CaO·SiO₂ does not exist in cement→ Portland cement — raw materials and compounds
Test yourself on Industrial and Applied Chemistry
10 past NDA questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.