Cotton, being a good absorber of sweat, absorbs the sweat and helps in increasing the speed of the evaporation by increasing the surface area and exposing it to the atmosphere. Problem 2.
How does water kept on earthen pot matka keep cool? Solution: When we kept water on the earthen pot matka , the water molecules evaporate from the several tiny pores of the pot. During this process, it takes the heat from the water and thus the water cools down due to the loss of heat.
This is the reason why water kept in earthen pot keep cool. Problem 3. We often sprinkle water on the ground or on the roofs during summers. Solution: This is because when we sprinkle water over the ground or roof top, the water from there evaporates taking the heat from the ground or roof top and in the process making it cool. Problem 4. We are able to sip hot tea of milk on a saucer rather than a cup.
Give reasons. Skip to content. Change Language. Related Articles. Table of Contents. Save Article. Improve Article. Like Article. Last Updated : 05 Aug, Fig 1. Next Worksheets in Excel. Recommended Articles. Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Water, for example, with one oxygen and two hydrogen atoms, can form two hydrogen bonds per molecule.
Its heat of evaporation is 2, joules per gram, or calories per gram, and it starts boiling at degrees Celsius degrees Fahrenheit. Your body makes use of the evaporative process when sweating.
Sweat, which consists of 90 percent water, starts to evaporate. The necessary heat of evaporation is extracted from the sweat itself, which leads to a heat transfer from the liquid into the gaseous state. This results in a cooling effect called evaporative cooling that helps to maintain body temperature and cools the body down when it gets too hot. The degree of cooling is dependent on the evaporation rate and heat of evaporation.
In this activity you will find out which liquid has a greater cooling power: rubbing alcohol or water. What do you think will cool more when it evaporates?
Observations and results Did you feel the cooling power of water and rubbing alcohol? Both liquids should feel cold on your skin. Blowing on your wet hand helps the water and alcohol to evaporate. The airflow will also support the heat transfer away from your skin. You should have noticed that your skin feels much cooler when you put the rubbing alcohol on your hand compared with the water.
The water and the alcohol will start to evaporate once you start blowing on your hand. Compared with water, alcohol has a lower heat of evaporation. That means that for the same amount of liquid, more heat transfer occurs during the evaporation of water compared with the alcohol. This does not fit your observation that alcohol has a greater cooling effect than water, however. The reason for that is that the amount of heat transfer also depends on the evaporation rate.
As alcohol evaporates at a much faster rate compared with water due to its lower boiling temperature 82 compared to degrees C , it is able to carry away more heat from the skin. This means for a given amount of time much more alcohol evaporates than water. The water is ideal for locating evaporation ponds for the extraction of not only table salt, but also magnesium, potash, and bromine.
We said earlier that heat is removed from the environment during evaporation, leading to a net cooling; notice how cold your arm gets when a physician rubs it with alcohol before pulling out a syringe with that scary-looking needle attached. In climates where the humidity is low and the temperatures are hot, an evaporator cooler, such as a "swamp cooler" can lower the air temperature by 20 degrees F. As this map shows, evaporative coolers work best in the dry areas of the United States red areas marked A and can work somewhat in the blue areas marked B.
In the humid eastern U. Here is Fido, looking both sharp and cool as he sports the latest in fashionable dog apparel that also keeps him cool on a hot day. Fido is wearing a "cooling vest", where the owner wets it down, places it on the dog, and the properties of the evaporation process help the dog stay comfortable.
Yes, swamp coolers aren't just for homes anymore. After all, the evaporative process is just as happy keeping a dog cool as it is keeping a house cool. Evaporative coolers are really quite simple devices, at least compared to air conditioners. Swamp coolers pull in the dry, hot outdoor air and pass it through an evaporative pad that is kept wet by a supply of water. In a home device, a fan draws the air through the pad, the water in the pad evaporates, resulting in cooler air which is pumped through the house.
Much less energy is used as compared to an air conditioner. Source: California Energy Commission. Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. The air is full of water, even if you can't see it. Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water droplets—clouds.
When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail What is streamflow? How do streams get their water? To learn about streamflow and its role in the water cycle, continue reading. Perhaps you've never seen snow. Or, perhaps you built a snowman this very afternoon and perhaps you saw your snowman begin to melt.
Regardless of your experience with snow and associated snowmelt, runoff from snowmelt is a major component of the global movement of water, possibly even if you live where it never snows.
The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Well as the highest kinetic energy things escape and those are the ones that are most likely to escape, well then your average kinetic energy is going to go down.
So average kinetic energy is going to go down. Or another way of saying it, is that your temperature is going to go down. Your temperature is going to go down because as these molecules turn into water vapor, they're going to be the highest kinetic energy, energy is transferred to them, and then they escape. And so what's left over is going to have a lower average kinetic energy.
And you're saying, "Well, how does that "actually cool down my hand? So let's say this is the surface of your hand, those are the molecules, they have some average kinetic energy, they are kind of vibrating in place, especially if we're talking about they're And so maybe I'll draw the more, you know, they're vibrating like this, they're bonded to each other in some way.
I won't go into the details of what types of molecules these are, but then if you have your water molecules here, water molecules that are sitting on the surface, and I'm drawing this is kind of a cross-section. Let me draw the water molecules. I'll draw them as blue molecules. So this is an H2O right over here. This is an H2O. And this is an H2O. And they have some hydrogen bonding, so there is some hydrogen bonding going on.
Well, as the high kinetic energy water molecules escape, I'll say this one right over here escapes, and so the average kinetic energy of what's left over is lower, so then the temperature has gone down, and now your body molecules, the ones that are all warmed up, and because of whatever's going on inside of your body, well, those can now bump into, they can vibrate and bump into these water molecules and increase their kinetic energy more than the ones that have the most kinetic energy.
Those might escape again.
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