# Angle of Contact – Definition, Importance and Characteristics

By BYJU'S Exam Prep

Updated on: September 25th, 2023

The angle of contact is determined by the composition of the liquid, the solid in contact, and the medium above the liquid’s free surface. Before we define the angle of contact, let’s define surface tension first. Any liquid’s surface tension is a trait that causes it to try to minimize its free surface area. The force operating per unit length on an imaginary line drawn tangentially on the free surface of a liquid is known as surface tension. The angle formed by the meniscus and the enclosing walls of a liquid column when measured from the vertical wall beneath the liquid’s surface to the position of the tangent to the meniscus at its point of contact with the wall.

The liquid and solid characteristics in contact and the medium above the liquid’s free surface determine the angle of contact. A glass capillary tube becomes water-proof when the wax is applied to it. The contact angle widens and becomes obtuse. It does not hold water. Instead, the obtuse angle of contact causes it to descend into the tube. Here we will see the definition of contact angle, the factors which the angle of contact depends upon and the characteristics of the angle of Contact.

Table of content

## What is the Angle of Contact?

The angle of contact is defined as the angle subtended between the tangents drawn at the liquid surface and the solid surface inside the liquid at the point of contact. The angle of contact is defined as the angle subtended between the tangents drawn at the liquid surface and the solid surface within the liquid at the point of contact or as the angle subtended between the tangents pulled at the liquid surface and the solid surface within the liquid at the point of contact.

The composition of the liquid, the solid in contact, and the medium above the liquid’s free surface all influence the angle of contact. The angle of contact increases as the temperature of the liquid rises. The angle of contact decreases when soluble pollutants are added to a liquid.

## Definition of Angle of Contact

“It is defined as the angle subtended between the tangents drawn at the liquid surface and the solid surface inside the liquid at the point of contact.”

• As the temperature of the liquid rises, so does the angle of contact.
• When soluble impurities are added to a liquid, the angle of contact decreases.

The angle of contact depends upon

• Medium above the liquid’s free surface.
• Liquid’s characteristics
• Solid in contact

## Importance of Angle of Contact

The angle of contact between the surface of the solid and the tangent drawn to the free surface of the solid and the tangent drawn to the free surface at the point of contact measured inside the liquid is defined as the angle between the surface of the solid and the tangent drawn to the free surface of the solid and the tangent drawn to the free surface at the point of contact measured inside the liquid. The contact angle controls whether a liquid will spread or form droplets on a solid’s surface.

• If the contact angle is obtuse, a droplet will be created.
• If the contact angle is acute, the water will spread.

## Characteristics of Angle of Contact

The following are the features of contact angle: It is constant for a certain liquid-solid pair and is determined by the sort of solid that comes into contact with the liquid. The rest of the parameters remain unaltered. The angle at which the solid touches the liquid surface has no bearing on it. It is affected by surface tension. As the surface tension varies, the temperature and purity of the liquid fluctuate. The medium above the liquid’s free surface determines it.

 Property Angle of Contact <90 Degree Angle of Contact = 90 Degree Angle of Contact >90 Degree Substance Water and Glass Water and Silver Mercury and Glass Meniscus Shape Concave Plane Convex Capillary Action Liquid Rises No Effect Liquid Falls Sticking to Solid Wet Does not wet Does not wet Liquid Surface’s Shape Almost Round Spreads Across the Surface Flat
POPULAR EXAMS
SSC and Bank
Other Exams
GradeStack Learning Pvt. Ltd.Windsor IT Park, Tower - A, 2nd Floor, Sector 125, Noida, Uttar Pradesh 201303 help@byjusexamprep.com