Which one among the following statements is not true for glass ?
- A.Sodium silicate is known as water glass.
- B.Glass is also called super cooled liquid.
- C.Crystallinity develops on cooling of the molten mass of the glass.
- D.Coloured glasses can be made by adding different colouring materials.
Correct answer
Explanation
The correct answer is C, Crystallinity develops on cooling of the molten mass of the glass. This is the false statement: glass cools into an amorphous solid without any regular crystal structure.
When molten glass cools, its viscosity rises so quickly that the atoms have no time to arrange themselves in an ordered crystal lattice. The disordered arrangement of the liquid is frozen in place, which is why glass is called an amorphous solid or a supercooled liquid, and why it has no sharp melting point but softens over a range of temperatures. Ordinary soda-lime glass is made by fusing sand, soda ash and limestone.
Option A is true: sodium silicate dissolves in water and is called water glass. Option B is true: glass is often described as a supercooled liquid. Option D is true: metal oxides colour glass, for example cobalt oxide gives blue and chromium oxide gives green.
Exam tip: glass is amorphous (no crystals, no sharp melting point); sodium silicate is water glass.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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