Question

4. Draw what the sample of water would look like on the molecular level at 110°C. (Be sure to draw and label the strongest interaction present as well as explain your drawing if needed) 5. Draw what the sample of water would look like on the molecular level at 100°C, the phase change. (Be sure to draw and label the strongest interaction present as well as explain your drawing if needed) 6. What interactions and/or bonds are overcome at 0°C? 7. What interactions and/or bonds are overcome at 100°c? 3. What would be the enthalpy for this process

Answer 1

4. at 110 C ( at 1 atm) water will be vapour phase after phase transition it is in gaseous state . Now , no more hydrogen bonds exist . Water molecules behave as individual entity any interaction among molecules depends on volume , and any interaction is vander-waal type interaction (..............................).

H-O-H ......................... H-O-H H-O-H H-OH

H-O-H H-O-H.................... H-O-H  

H-OH (WATER VAPOURS) H-O-H

5. At 100 C water is undergoing phase change , it use latent heat of vaporization to overcome strong molecular interactions present in the form of H-Bonds : now water has two phases liquid phase and gaseous phase , interactions in gaseous phase are limited by vanderwaal's distance and volume , liquid phase has H-bonds which are under-going bond breaking.

H-O-H ......................... H-O-H H-O-H H-OH

H-O-H H-O-H.................... H-O-H  

H-OH (vapour phase ) H-O-H

....................................................................................................................................(phase boundary)

H-O-H ............ H-O-H.............H-O-H    H-OH.....................H-O-H..............H-O-H

H₂O........H₂O...........H₂O...........H₂O...........H₂O............H₂O.......H₂O........H₂O........H₂O

OH₂........ OH₂ .....OH₂........OH₂.......OH₂........OH₂........OH₂........OH₂........OH₂........ (H-bonds) (liquid phase )

6. 0 C is fusion temperature for water , at this T phase transition between solid and liquid phase occurs. During melting, energy goes exclusively to changing the phase of a substance

H₂O(s) → H₂O(ℓ)

Water have H-Bonding in both liquid and solid phase but difference is there : ice has stronger hydrogen bonds than liquid water on average, In liquid state of water atoms having kinetic energy , so they cannot form permanent bonds. In ice water molecules are under force of Crystal packing, while melting this crystal packing breaks (energy is needed to overcome this crystal packing ) and New H-bonds form in liquid .

7. At 100 C water is undergoing phase change , it use latent heat of vaporization to overcome strong molecular interactions present in the form of H-Bonds.

8. Enthalpy for process of melting and boiling will be +ve as energy is consumed to overcome molecular interaction forces.