An emulsion consists of
- A.one liquid and one solid
- B.one liquid and one gas
- C.two liquids
- D.two solids
Correct answer
Explanation
The correct answer is C, two liquids. An emulsion is a colloid in which tiny droplets of one liquid are spread through another liquid with which it does not mix.
Colloids are classified by the state of the dispersed phase and the dispersion medium. When both are liquids, the colloid is an emulsion. Milk is an emulsion of liquid fat in water, and butter is the reverse type, water in fat. Mayonnaise, cold cream and many medicinal lotions are other examples. Because oil and water separate on standing, an emulsifying agent such as soap, detergent, egg yolk or the proteins in milk is used to keep an emulsion stable. Soap cleans greasy cloth by turning the oil into an emulsion that water can wash away.
Option A is wrong because a solid dispersed in a liquid is a sol, such as paint or starch solution. Option B is wrong because a gas dispersed in a liquid is a foam, such as shaving cream or soda froth. Option D is wrong because a solid in a solid is a solid sol, such as coloured gemstones.
Exam tip: liquid in liquid = emulsion (milk); solid in liquid = sol; gas in liquid = foam; liquid in gas = aerosol (fog).
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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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
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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