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Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

Property of fluid by which its own molecules are attracted is called 

  1. adhesion

  2. cohesion

  3. viscosity

  4. compressibility
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cohesion is the intermolecular attractive force acting between two adjacent portions of a substance within itself, particularly of a fluid. It is this force that holds a piece of matter together. 

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

Attractive forces of cell walls for water molecules is termed as

  1. Adhesion

  2. Cohesion

  3. Osmosis

  4. Plasmolysis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another.

Cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another.
Example of cohesion - attractive force between water molecules and adhesion - attractive force between water and xylem channels.

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

A piece of ice. With a stone frozen inside it, is floating in water contained in a beak. When the ice metls,the level of water in the beaker.

  1. Rises

  2. Falls

  3. Remains uncharged

  4. Fall at first and then rises to the same height as before.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When ice melts, the volume of water displaced by the ice (Archimedes' principle) is equal to the volume of the water formed by the melted ice. The stone's displacement remains the same. Thus, the water level remains unchanged.

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

The surface tension and vapour pressure of water at $20^oC$ is 7.28$ \times10^{ -2 }$ N/m and $2.33 \times { 10 }^{ 3 }$ pa, respectively. What is the radius of the smallest spherical water droplet which can from without evaporating at $20^oC$ ?

  1. $5\times { 10 }^{ -4 }m$

  2. $6.25\times{10}^{-5}m$

  3. $9\times{10}^{-2}m$

  4. $3\times{10}^{-5}m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

 Work done in increasing the size of a soap bubble from a radius of $3\ cm$ to $5\ cm$ is nearly (Surface tension of soap solution$=0.03\ {Nm}^{-1}$):

  1. $0.2\pi\ mJ$

  2. $2\pi\ mJ$

  3. $0.4\pi\ mJ$

  4. $4\pi\ mJ$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Work done = Surface Tension * Change in Surface Area. A soap bubble has two surfaces, so Area = 2 * (4 * pi * r^2) = 8 * pi * r^2. Change in Area = 8 * pi * (r2^2 - r1^2) = 8 * pi * (0.05^2 - 0.03^2) = 8 * pi * (0.0025 - 0.0009) = 8 * pi * 0.0016 = 0.0128 * pi m^2. Work = 0.03 * 0.0128 * pi = 0.000384 * pi J = 0.384 * pi mJ, which is approximately 0.4 * pi mJ.

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

The dimension of sphere of influence of an molecules is

  1. $1 A^o$

  2. $10 A^o$

  3. $100 A^o$

  4. $0.1 A^o$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


The Molecular range is the radius around a molecule in a substance to which the molecule can exert attraction force on another molecule$.$  This is distance$,$
Sphere of influence is the spherical space/volume around a molecule in a substance$,$ inside which the molecule at center can exert attractive force on another molecule$.$
The molecular range is very small like $1 nanometer.$
Surface tension is the surface energy $-$ additional energy required to increase surface by a unit area$.$  This is also the tension force exerted $($along the line$)$ on the boundary of a surface per unit length$.$
Hence,
option $(A)$ is correct answer.
Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

If $2$ bubble of radius $r _1$ & $r _2$ are combined then find radius of common surface.

  1. $\dfrac{r _1r _2}{r _1+r _2}$

  2. $\dfrac{r _1r _2}{r _1-r _2}$

  3. $\sqrt{r _1r _2}$

  4. $\dfrac{r _1+r _2}{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When two bubbles of radii r1 and r2 are joined, the radius of the common interface r is given by 1/r = 1/r1 - 1/r2 (assuming r1 < r2). Thus, r = (r1 * r2) / (r2 - r1).