7 (a) Use the kinetic particle theory of matter to explain why energy is needed to melt a solid, at its melting point, to form a liquid. - [2] (b) A student puts a drop of coloured ink into water. The ink slowly spreads throughout the water. Use the kinetic particle theory of matter to explain this observation. ​

7 (a).

» At melting point, temperature is constant and there is increase in vibràtory energy of solid molecules increases. In that case, the mobílity or lovomotive degree of the solid molecules because the intermolecular forces between them have became weaker. Hence molecules become further apart from each other hence a liquid formed.

(b).

The molecules of the ink get bonded to the water molecules. Since water molecules have a high degree of mobílity or locomotion in different directions, the ink molecules also tend to move in different directions hence water turns colored.

Explanation:

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