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 (B)</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 (D)</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. (D)</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. (D)</p> Signup and view all the answers

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

<p>It becomes zero. (A)</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. (B)</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. (C)</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 (A)</p> Signup and view all the answers

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

<p>Less than 90° (A)</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 (C)</p> Signup and view all the answers

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

<p>Fa &gt; Fc (D)</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 (A)</p> Signup and view all the answers

What is the angle of contact for water and chromium?

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

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

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

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

<p>Flat (C)</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 (A)</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 (B)</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° (B)</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 (A)</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 (D)</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 (D)</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 (D)</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 (A)</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 (B)</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 (B)</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 (D)</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 (A)</p> Signup and view all the answers

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