Embibe Experts Solutions for Chapter: Viscosity and Surface Tension, Exercise 7: Exercise (Assertion & Reason)

Assertion: Surface tension of liquid decreases with increase in temperature.

Reason: Cohesive force between liquid molecules increase with increase in the temperature.

Assertion: A thin stainless steel needle can lay floating on still water surface.

Reason: Any object floats when the buoyant force balances the weight of the object.

Assertion: Surface energy of an oil drop is same whether placed on glass or water surface.

Reason: Surface energy is dependent only on the properties of oil.

Assertion : Surface tension is the property of only liquids
Reason : Only liquids have free surface in fluids.

Assertion : Soil particles inside water are freely placed but they stick together when taken out of water.
Reason : Thin film formed creates pressure difference.

Assertion: When temperature of a liquid is increased, then its surface tension decreases.

Reason: Kinetic energy and oscillations of molecules increases, so intermolecular force of attraction decreases.

Assertion: Surface tension of water is larger among fluids.

Reason: There is hydrogen bond in water molecules, so its surface tension is larger than other fluids.

Assertion : Viscous force opposes relative motion between fluid layers.  
Reason : Some kinetic energy is lost in form of heat.