Hard problems How much boiling water would you need to add to a cup with 100.0 g of ice and 100.0 g of water at equilibrium to get all the ice to melt? (hard)  If you doubled that amount of water what would the final temperature be? (hard) Ī new look If 90.0 g of water at 300.

How much energy is required to vaporize 10.0 g of water? (easy) How much energy is required to melt 10.0 g of water? (easy) How much energy would it take to raise the temperature of ice at 268 K to 378 K? (getting harder)

 If any of the water were to increase in temperature that energy would immediately be transferred to the ice to cause it to melt. ΔHvap and ΔHfus Melting ice and boiling water are both endothermic processes and as such they both require energy.  For similar reasons, the temperature of boiling water will never exceed 373 K. Only after all the ice melts will the temperature begin its crawl up to room temperature. ΔHvap and ΔHfus If you put a thermometer in a glass of ice water, the temperature will read 273 K until all the ice melts.  Today we’re going to extend that lesson to include phase change. ΔHvap and ΔHfus Last unit we looked at the change in enthalpy associated with a chemical reaction and the energy flow as materials (mostly water) are heated.

Which do you think is favored by nature?  Why?   We have seen both endothermic and exothermic processes in lab. Enthalpy is related to the amount of energy that is lost or gained by a system during a normal chemical process. Bartelt Presents The greatest fight in the universeĮnthalpy We already know about enthalpy.

Enthalpy vs entropy