FORM 1-PHYSICS-STRUCTURE AND PROPERTIES OF MATTER
STRUCTURE AND PROPERTIES OF MATTER
The Concept of Adhesion and Cohesion
Explain the concept adhesion and cohesion
Matter is made up of molecules. That exerts force of attraction. This force of attraction may be either Cohesion or Adhesion.
- Cohesion is the force of attraction between the molecules of the same substance, example water to water molecules.
- Adhesion is the force of attraction between the molecule of different substances example water to glass molecules.
Water molecules can experience the force of cohesion among themselves, where water molecules and glass molecules will experience force of adhesion.
Definite shapes of a solid are due to strong cohesion force among its molecules.
Shapes and meniscus of a liquid
When we carried out activities involving determination of volume in a liquid ring and measuring cylinder. The description indicated that the surface of the liquid was carved, forming a meniscus, and that the volume must be read at the bottom or top of the meniscus, depending on the liquid used. For mercury, the top of the meniscus is read.
The formation of a meniscus in a liquid is due to forces of adhesion between the liquid and the walls of the container. The adhesion of the liquid such as water to the wall of a vessel causes an upward force on the liquid at the edge.
The opposite takes place in mercury, the meniscus of water curves upwards forming a concave shape. When a drop of each liquid, mercury and water are placed on a glass sheet, water spreads further unlike mercury, because of mercury’s high cohesion force among its particle.
Why water wets the glass?
Why methanol does not wet the glass?
Applications of Adhesion and Cohesion in Daily Life
Identify the applications of adhesion and cohesion in daily life
Application include the following
- To stick two different objects together. Here we use the adhesive effects of tape or glue.
- Adhesion can also be used to remove harmful materials such as bacteria from drinking water. Adhesive forces are the source attraction substance.
- Cohesion assists in transport of water in plants and animals by allowing one molecule to pull others along with it.
- The bodies of plants and animals also use the cohesion of tissue to repair damage.
- Ink sticks on paper because of adhesive force between the paper and ink.
