Soap with water forms:
- A.Metallotropic liquid crystal
- B.Thermotropic liquid crystal
- C.Homogeneous solution
- D.Lyotropic liquid crystal
Correct answer
Explanation
The correct answer is D, Lyotropic liquid crystal. Soap in water forms a lyotropic liquid crystal, a phase whose ordered structure appears because of the amount of solvent mixed in, not because of temperature alone. Liquid crystals are states of matter between a solid crystal and an ordinary liquid: they flow like a liquid but their molecules keep some order. Soap molecules have a water-loving ionic head and a long water-hating hydrocarbon tail. In water they gather into micelles, and at higher concentrations they pack into layers, rods or other ordered phases. Because this order depends on concentration in a solvent, the phase is called lyotropic; cell membranes and many detergents show the same behaviour. Option A is wrong because metallotropic liquid crystals involve metal-containing compounds and are not what soap forms. Option B is wrong because thermotropic liquid crystals change phase with temperature and are used in LCD screens and thermometer strips. Option C is wrong because soapy water is not a true homogeneous solution; the soap forms micelles, giving a colloidal system. Exam tip: lyotropic = depends on solvent concentration (soap); thermotropic = depends on temperature (LCD).
Practice Questions
View allA recent movie titled The Man Who Knew Infinity is based on the biography of
- A.S. Ramanujan
- B.S. Chandrasekhar
- C.S. N. Bose
- D.C. V. Raman
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The 2015 film 'The Man Who Knew Infinity' tells the life of the Indian mathematician Srinivasa Ramanujan and is based on Robert Kanigel's 1991 biography of the same name.
Read the full explanation →The word 'Denisovan' is sometimes mentioned in media in reference to
- A.fossils of a kind of dinosaurs
- B.an early human species
- C.a cave system found in North-East India
- D.a geological period in the history of Indian subcontinent
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Read the full explanation →Which one of the following statements best describes the role of B cells and T cells in the human body?
- A.They protect the body from environmental allergens.
- B.They alleviate the body's pain and inflammation.
- C.They act as immunosuppressants in the body.
- D.They protect the body from the diseases caused by pathogens.
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Read the full explanation →Which one of the following is not used as fertilizer?
- A.Ammonium nitrate
- B.Ammonium sulphide
- C.Ammonium phosphate
- D.Ammonium sulphate
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Ammonium sulphide is an unstable, foul-smelling compound that breaks down to release ammonia and toxic hydrogen sulphide, so it is not used as a fertiliser.
Read the full explanation →The focal length of the objective lens of a telescope is 50 cm. If the magnification of the telescope is 25, then the focal length of the eye-piece is
- A.12.5 cm
- B.5 cm
- C.2 cm
- D.10 cm
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For an astronomical telescope in normal adjustment the magnifying power equals the focal length of the objective divided by that of the eyepiece, so the eyepiece focal length is 50 ÷ 25 = 2 cm.
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