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12.4 Intermolecular Forces in Action: Surface -- Part 2
40.7 kJ of heat is released when one mole of water condenses.
The mass of water can be calculated with 155 kJ of heat.
155 kJ was asked to find the mass of water.
If you want to convert the moles of water to the mass of water, use the molar mass as a conversion factor.
To solve the problem, follow the conceptual plan.
If 0.25 g of water is at 25 degC, it will condense on the surface of a 55 g block of aluminum.
If a container of water is left uncovered at room temperature, the water will slowly evaporate away.
In the open beaker, the water molecule evaporate as they do in the open beaker.
The evaporated molecule cannot escape into the atmosphere because of the seal.
Water begins to evaporate when it is in a sealed container.
As water builds up in the gas state, it begins to recondense into the liquid.
The intermolecular forces can be overcome by thermal energy.
When the rate of condensation lar forces result in nonvolatile substances with low vapor pressures, it's called strong intermolecu.
A balanced system with a liquid and Vapor tends to return to equilibrium if disturbed.
pentane is a component of gasoline and can be found at 25 degC in a cylinder.
The pressure in the cylinder is 510mmHg.
The pressure in the cylinder goes below 510mmHg in Section 6.3.
Once equilibrium is reached again, more liquid will evaporate.
pentane brings the system back into equilibrium.
The pressure in the cylinder goes up to 510mmHg, but then some of the gas goes into liquid until equilibrium is reached again.
Pressure falls as volume is decreased.
pentane is in equilibrium.
When the volume increases, the pressure goes down and some liquid converts to gas.
When the volume is reduced, the pressure increases and some gas converts to liquid to bring the pressure back down.
When a system in dynamic equilibrium is disturbed, the system responds by returning to a state of equilibrium.
The equilibrium pressure can be restored if the pressure above a liquid-vapor system decreases.
The pressure can be brought back down to the equilibrium pressure if the pressure increases.
In Chapter 16 we will see that this principle is applicable to any chemical system in equilibrium.
The pressure is the same.
When the temperature of a liquid increases, the number of molecules that have enough energy to evaporate increases.
Because of the shape of the thermal energy distribution curve, a small change in temperature makes a big difference in the number of molecules that have enough energy to evaporate.
The vapor pressure of water at 25 degC is 23.3 torr, while at 60 degC it is 149.4 torr.
Vapor pressure increases with increasing temperature because more molecule have enough thermal energy to escape into the gas state.
When thermal energy is high enough, the molecules in the interior of the liquid become gaseous, forming bubbles that rise to the surface.
The hot water has bubbles in it.
These bubbles are dissolved into water or steam.
The boiling point of water is 100 degrees.
If you heat the water at a lower temperature, it will boil at a lower pressure.
In Denver, Colorado, where the altitude is around 1600 meters, the average atmospheric pressure is about 83% of the temperature, and the amount of gas in a liquid decreases with elevation.
Chapter 14 was taken for this reason.
The boiling point of water is listed in Table 12.8.
The atmospheric pressure in each location is subject to weather conditions.
boiling water always has a temperature of 100 degrees.
The temperature cannot rise above its boiling point if liquid water is present.
The steam temperature can continue to rise after all the water has been converted to steam.
Figure 12.28 shows the boiling point of water at an external pressure of 200 torr.
Let's look at Figure 12.28.
The graph shows that the vapor pressure of a liquid increases with temperature.
The temperature of the water remains at 100 degrees.
This is a common method for analyzing chemical data.
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