Which of the following statements is NOT correct about surface tension?
- A.Surface tension is typically measured in dynes/cm.
- B.The shape of water drop is spherical due to surface tension.
- C.At room temperature, surface tension of water is less than ethyl alcohol.
- D.The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension.
Correct answer
Explanation
The correct answer is C, At room temperature, surface tension of water is less than ethyl alcohol. This is the statement that is not correct, because water has a much higher surface tension than ethyl alcohol. At about twenty degrees Celsius water measures close to seventy two dynes per centimetre while ethyl alcohol is only about twenty two, since the hydrogen bonds between water molecules pull far more strongly than the weaker forces inside alcohol. That is also why alcohol spreads out thinly on a surface while water gathers into beads. A is a correct statement, because surface tension is expressed in dynes per centimetre in the older unit system and in newtons per metre in the SI system. B is correct, because the inward pull on the surface gives a small free drop the shape with the least area for its volume, which is a sphere. D is correct, because surface tension arises from the cohesive forces among the molecules of the liquid itself. Exam tip: water is about 72 dynes per centimetre and alcohol about 22; surface tension falls as temperature rises.
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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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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