- Newton per meter
Hello dear students, we know that intermolecular force of attraction between molecules of solid is strong so that solid possesses definite shape and size, whereas this force is weak in liquid so the liquid do not possess definite shape. Along with this liquid possess very important property called surface tension. To have minimum potential energy, molecules at liquid surface tend to reduces area to minimum value. Thus, liquid surface behave as a stretched membrane. This tendency of liquid surface is known as surface tension.
It is defined as the force per unit length. OR
The force acting per unit length of imaginary line drawn on free liquid surface at right angles on either sides of the line.
If L is the length of line & F is the force acting on it, the surface tension (T) is given by,
∴ T = F/L
From the above formula, SI unit of surface tension is then given as,
∴ T = newton/meter
i.e. N/m or N.m-1
Important Faq
Q.1) How surface tension can help to reduce the growth of mosquitoes?
Answer: Mosquito eggs floats on the water surface due to ST of water. When kerosene is spreads on the water surface, the surface tension of water lowered & eggs go down inside the water & the breeding of mosquito’s stops.
Q.2) What factors affects the surface tension?
Answer: Following are the factors affecting surface tension:
1.) Presence of impurity a) Highly soluble substances when dissolved in the liquid, the surface tension of liquid increases.
b) Lightly soluble substances when mixed with liquid then surface tension of liquid decreases. i.e. Phenol in water
2.) Temperature: Rise in temperature decreases surface tension of liquid.
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