Question

6. Define cohesive forces. How does its value
change for three different states of matter?
7. Describe the effect of heat on a solid, a liquid
and a gas in terms of expansion.
8. What happens when common salt is
dissolved in water? Explain briefly.​

Answer 1

• cohesive forces are the intermolecular forces( such as those from hydrogen bonding and van der Waka forces) which cause a tendency in liquids to resist separation. these attractive forces exist between molecules of the same substance.

• All three states of matter (solid, liquid and gas) expand when heated. The atoms themselves do not expand, but the volume they take up does. When a solid is heated, its atoms vibrate faster about their fixed points. ... An increase in temperature results in the expansion of the liquid which means it rises up the glass.

• Water molecules pull the sodium and chloride ions apart, breaking the ionic bond that held them together. After the salt compounds are pulled apart, the sodium and chloride atoms are surrounded by water molecules, as this diagram shows. Once this happens, the salt is dissolved, resulting in a homogeneous solution.