Author Question: Using the concept of supercooled water, explain why ice cubes sometimes feel sticky when taking them ... (Read 79 times)

jjjetplane · **on:** Jul 13, 2018

Using the concept of supercooled water, explain why ice cubes sometimes feel sticky when taking them out of the freezer.
What will be an ideal response?

Question 2

What is meant by the terms water vapor saturation and saturation vapor pressure? Why does the saturation vapor pressure increase with increasing air temperature?
What will be an ideal response?

frre432 · **Reply #1 on:** Jul 13, 2018

Answer to Question 1

ANSWER: Student answers may vary slightly. When we press on an ice block or icy surface with our fingers, the pressure that we apply causes an instant and localized melting on the ice surface under the fingers. Melting is also encouraged by our fingers' higher temperature. The layer of melted liquefied water freely flows into the grooves of our fingers where it freezes again. When we pull our fingers away from the ice we have to break the thin film of ice that connects our skin and the ice cube, which is why it feels sticky'.

Answer to Question 2

ANSWER: Student answers need to state that water vapor saturation means that for every water molecule that evaporates, one must condense, and no net loss of liquid or vapor molecules results. Saturation vapor pressure describes how much water vapor is necessary to make the air saturated at any given temperature. Put another way, saturation vapor pressure is the pressure that the water vapor molecules would exert if the air were saturated with vapor at a given temperature. Saturation vapor pressure increases with temperature because the number of fast-moving molecules increases as the temperature increases and, due to the temperature increase, the number of water molecules escaping per second also increases. To maintain equilibrium, the situation causes an increase in the number of water vapor molecules in the air above the liquid. Consequently, at higher air temperatures, it takes more water vapor to saturate the air. And more vapor molecules exert a greater pressure. Hence, saturation vapor pressure depends primarily on the air temperature.