Liquid
Liquid is made up of small vibrating atoms or molecules held together by chemical bonds. The intermolecular forces in liquids are weaker than solids but stronger than gases. The most common example of liquid on the Earth is water that covers 71% of its surface.
Due to weak attraction forces liquids have definite volume, but no fixed shape. They are not rigid like solids and hence take the shape of their container. Liquids can flow easily as atoms and molecules in them exhibit greater freedom to move. Because of little free space between particles, liquids can not be compressed unless high pressure is applied to their surface.
The surface molecules of liquid can evaporate easily. The rate of evaporation depends on the surface area, temperature and humidity of the air. On heating, liquids can be converted into gases, whereas on cooling they can solidify.
Cohesive forces between water molecules
Adhesive forces between water molecule and leaf
Cohesive and Adhesive Forces:
Liquids do possess some distinct properties due to cohesive and adhesive forces.The cohesive forces (the attraction force between
like molecules) between the molecules of liquids are responsible for surface tension. The molecules on the surface do not have any
like molecules above them and hence, they cohere more strongly to their neighboring surface molecules. Consequently, the surface
of the liquid contracts to the smallest possible surface area. This effect is called surface tension.
On the contrary, adhesive forces are the attraction forces between unlike molecules. The formation of water drops is the result
of cohesion but adhesion keeps these drop in place (e.g., drops cling to the surface of the leaf due to adhesive force).
Liquids as solvents:
Liquids are very useful as solvents. Many chemical reactions take place only in their suitable solvents. No one liquid can
dissolve all types of substances into it. Though, water is considered as universal solvent, it has its own limitations. Only polar
and ionic substances can be dissolved in water, while non polar substances are dissolved in non polar solvents such as benzene,
ether etc.