Surface Tension
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Questions and Answers

What is the range of values for the contact angle between a liquid and a solid?

  • Between 45o and 135o
  • Between 0o and 180o (correct)
  • Between 90o and 270o
  • Between 0o and 90o

    • What happens to the contact angle when the temperature is increased?

  • It increases
  • It becomes zero
  • It remains the same
  • It decreases (correct)

    • What is the effect of soluble impurities on the contact angle?

  • It decreases the contact angle
  • It has no effect on the contact angle
  • It increases the contact angle (correct)
  • It makes the contact angle zero

    • What is the root cause of capillarity?

    <p>Difference in pressures on two sides of a curved surface</p> Signup and view all the answers

    What happens to the liquid in a capillary tube?

    <p>It ascends or descends relative to the surrounding liquid</p> Signup and view all the answers

    What is the reason for the irregularly shaped camphor to move haphazardly on the surface of pure water?

    <p>The irregular shape of camphor dissolves unequally and decreases the surface tension of the water locally.</p> Signup and view all the answers

    Why do rain drops tend to acquire a spherical shape?

    <p>Each drop tends to acquire minimum surface area.</p> Signup and view all the answers

    What happens to the surface tension of a liquid at its boiling point?

    <p>It becomes zero.</p> Signup and view all the answers

    Why does an oil drop spread on cold water but remain as a drop on hot water?

    <p>The surface tension of oil is less than that of cold water and more than that of hot water.</p> Signup and view all the answers

    What is the shape acquired by the detached portion of the liquid metal when it breaks up after being poured into water from a suitable height?

    <p>Spherical shape.</p> Signup and view all the answers

    What is the direction of the resultant force when the liquid meniscus is concave upward?

    <p>Outside the liquid</p> Signup and view all the answers

    What is the angle of contact when the liquid wets the solid surface?

    <p>Less than 90°</p> Signup and view all the answers

    What is the shape of the meniscus when the angle of contact is equal to 90°?

    <p>Plane</p> Signup and view all the answers

    What is the condition for the liquid to wet the solid surface?

    <p>Fa &gt; Fc</p> Signup and view all the answers

    What is the tangent of the angle of contact (α) when the resultant force is infinite?

    <p>Infinity</p> Signup and view all the answers

    What is the angle of contact for water and chromium?

    <p>138°</p> Signup and view all the answers

    What happens to the angle of contact when the temperature is increased?

    <p>It decreases</p> Signup and view all the answers

    What is the shape of the meniscus when the angle of contact is 90°?

    <p>Flat</p> Signup and view all the answers

    What is the effect of partially soluble impurities on the angle of contact?

    <p>It decreases the angle of contact</p> Signup and view all the answers

    What is the reason for the rise of a liquid in a capillary tube?

    <p>The pressure on the concave side of the meniscus is less</p> Signup and view all the answers

    What is the primary reason for the difference in pressure at points B and D in the capillary tube?

    <p>The angle of contact between the liquid and the capillary tube is not 90°</p> Signup and view all the answers

    What is the effect of an increase in temperature on the capillary rise of a liquid in a capillary tube?

    <p>The capillary rise increases due to a decrease in surface tension</p> Signup and view all the answers

    What is the shape of the meniscus in a capillary tube when the angle of contact is 0°?

    <p>Concave upwards</p> Signup and view all the answers

    What is the relationship between the radius of the capillary tube and the capillary rise?

    <p>The capillary rise is inversely proportional to the radius of the capillary tube</p> Signup and view all the answers

    What is the direction of the resultant force when the liquid meniscus is concave upwards and the angle of contact is less than 90°?

    <p>Upwards and along the vertical axis of the capillary tube</p> Signup and view all the answers

    What is the effect of temperature on the surface tension of a liquid?

    <p>It decreases with an increase in temperature</p> Signup and view all the answers

    What happens to the surface tension of water when a highly soluble substance like sodium chloride is dissolved in it?

    <p>It increases</p> Signup and view all the answers

    Why do detergents added to water increase the wetting power of the solution?

    <p>Because they decrease the surface tension of water</p> Signup and view all the answers

    What is the effect of sparingly soluble substances like phenol on the surface tension of water when dissolved in it?

    <p>It decreases the surface tension of water</p> Signup and view all the answers

    What is the effect of temperature on the surface tension of a liquid, as given by the relation Tt = T0 (1 - αt)?

    <p>The surface tension decreases with an increase in temperature</p> Signup and view all the answers

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