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12.4 Intermolecular Forces in Action: Surface -- Part 1
The blood is drawn into the tube by capillary action when the tube's tip comes into contact with the blood.
The force helps trees and plants draw water.
The cohesive forces cause the liquid to stay together while the adhesive forces cause it to spread.
Blood is drawn into a capillary tube by capillary action if the adhesive forces are greater than the cohesive forces.
The water rises up the tube until the force of gravity balances the capillary action--the thinner the tube, the higher the rise.
Liquid mercury does not rise up the tube if the glue force is less than the cohesive force, and it drops to a level below the surrounding liquid if the glue force is more than the cohesive force.
The difference in the relative magnitudes of cohesive and adhesive forces can be seen by comparing the meniscus of water to the mercury.
The liquid around the edge of the tube bonding between the atoms is larger than water because of the water molecule up the walls.
The mercury atoms crowd are more attracted to the glass column than to each other.
The higher the liquid will rise, the more mercury atoms will be attracted to one another.
Maintaining proper body temperature is dependent on maintaining proper Vaporization is a common occurrence that we experience every day.
The molecule are moving due to thermal energy.
If we were able to see the molecule at the surface, we would be able to see what a wild dance floor it would be.
Some molecules have more thermal energy than others and some have less.
Molecules in an open beaker have enough energy to leave a mark on the surface of the liquid.
The temperature is distributed over a range.
The peak energy increases with temperature.
The high end of the distribution curve has enough energy to break free from the surface due to fewer neighbor-neighbor interactions.
Some of the water molecule in the gas state, at the low end of the energy distribution curve for the gaseous molecule, plunge back into the water and are captured by intermolecular forces.
Vaporization and condensation occur in a beaker open to the atmo sphere, but under normal conditions, most of the newly evaporated molecules escape into the surrounding atmosphere and never come back.
The water level within an open beaker decreases over time.
The amount of water is spread over a larger area, resulting in more molecule at the surface of the liquid.
Molecules at the surface evaporate more quickly because they are held less tightly.
Water in a beaker or glass may take many days to evaporate completely, whereas the same amount of water spilled on a table or floor can evaporate within a few hours.
The rate of vaporization is increased by the weaker intermolecular forces.
Water is less volatile than acetone.
At room temperature, motor oil is nonvolatile.
Increasing temperature increases the rate of vaporization.
Increasing surface area increases the rate of vaporization.
The strength of intermolecular forces can affect the rate of vaporization.
Think about a beaker of water from the point of view of the molecule and imagine that the beaker is insulated so that heat from the surroundings cannot enter.
The most energetic are the ones that leave the beaker.
If there is no additional heat in the beaker, the average energy of the entire collection of molecules will go down.
One way to understand the endothermicity of vaporization is to remember the processes.
The process is endothermic because energy is needed to pull the molecule away from one another.
Our bodies use the endothermic nature of cooling.
Our skin is covered in liquid water when we sweat.
The water absorbs heat from the body and cools it.
A fan makes us feel cooler because it blows newly vaporized water away from our skin.
High humidity slows down the net rate of evaporation.
The body's cooling system is less efficient when the air contains large amounts of water vapor.
The burn is caused by the release of a lot of heat when the steam condenses to a liquid on your skin.
The reason for winter overnight temperatures in coastal effect is a cooling condensation of water vapor.
As the air temperature in a coastal area drops, water in the air condenses, releasing heat and preventing the temperature from dropping further.
The temperature drop in deserts is more extreme due to the lack of humidity in the air.
The boiling point of water is +40.7 kJ>mol, which is the pressure of 1 atm, as discussed later in this section.
The heat of the process is always positive.
The heat of vaporization is dependent on the temperature.
The water contains less thermal energy than at 100 degrees, so the heat of the water is slightly more than at 25 degrees.
The table shows the temperatures of liquids at their boiling points.
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