Question

What is the effect of temperature and impurity on the surface tension of a liquid?

Answer 1

1) surface tension of liquid decrease with increase in temperature as

T=T°(1-αФ)

only in case of molten copper and molten cadmium surface tension increase with increase n temperature .

2) due to addition of soluble impurity surface tension increase and due to addition of insoluble impurity surface tension decrease .

Answer 2

Answer:

The surface tension of a liquid increases by dissolving highly soluble impurities in the liquid. The surface tension of liquid decreases, by adding insoluble impurities.

Explanation:

• When the liquid surface has tendency to get to the minimum surface area possible, this tendency is called surface tension.
• The tension on the surface film caused by the attraction of molecules on the surface by the whole mass of the liquid is described by surface tension.
• The cohesive force between the molecules present at the surface and in the bulk of the liquid. The bulk molecules are trying to attract the surface molecules and making them to acquire the least possible surface area.
• The surface tension of liquid increases or decreases by adding impurities. It is determined by the cohesion between the molecules or the adhesion among the liquid molecules and impurity.
• For example, if we add NaCl salt in water.  The salt immediately breaks into Na⁺ and Cl⁻ ions which make much stronger attraction between the water molecules around these ions. Therefore,  the surface tension of water will increase.
• The surface tension of water decreases by adding oil to water. The surface tension will be reduced at the water surface, because the balancing force between the water molecules and oil molecules.