why stem at 100 degere Centrigrade is better for heating purpose then boiling water at 100 Celsius?

Answer 1

How much heat does it take to get water to change state? If the water is at a temperature of 100 degrees C (that is, the boiling point, or 212 degrees F) it takes an additional 540 calories of heat to convert one gram of water from the liquid state to the vapor state. When the vapor converts to the liquid state, 540 calories of energy will be released per gram of water. If you are converting solid water (ice) to liquid water at 0 degrees C, it will require about 80 calories of heat to melt one gram of ice, and the 80 calories will be released when the liquid water is frozen to the solid state.

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* Latent heat is the heat energy required to change a substance from one state to another.

There are basically three states of matter: solid, liquid, and gas. The difference between them is how the molecules are arranged. Solids have tightly-packed molecules, liquids are still bound together but not strongly enough to keep them from flowing, and gas molecules are free-flowing, not bound to one another at all. Energy is required to change from one state to another because bonds must be loosened, broken, tightened, or made. Energy must be given to the molecules if bonds are to be loosened or broken and taken from the molecules if they are to be tightened or made.
* Energy is required to change from solid to liquid, liquid to gas (evaporation), or solid to gas (sublimation). Energy will be released to change from liquid to solid (fusion), gas to liquid (condensation), or gas to solid.


* Latent heat of evaporation is the energy used to change liquid to vapor.

IMPORTANT: The temperature does not change during this process, so heat added goes directly into changing the state of the substance. About 600 calories of energy are needed for every gram of water at room temperature. This is why you cool when you step out of the shower. Heat is taken from your skin to evaporate the water on your body.
* Evaporation is a cooling process.


* Latent heat of condensation is energy released when water vapor condenses to form liquid droplets.

An identical amount of calories (about 600 cal/g) is released in this process as was needed in the evaporation process. This is one mechanism of how thunderstorms maintain their intensity. As moist air is lifted and cooled, water vapor eventually condenses, which then allows for huge amounts of latent heat energy to be released, feeding the storm.
* Condensation is a warming process.


* Latent heat of fusion describes both changing from solid to liquid and from liquid to solid.

From solid to liquid, about 80 calories per gram are needed. From liquid to solid, about 80 cal/g are released.
* Latent heat of sublimation describes both changing from solid to gas and gas to solid.

Sublimation is rare as compared to the other changes of state. From solid to gas 600 + 80 = 680 calories per gram are needed. From gas to solid, 680 cal/g are released.

Latent Heat
Each time water changes physical state, energy is involved.

In the vapor state, the water molecules are very energetic. The molecules are not bonded with each other, but move around as single molecules. Water vapor is invisible to us, but we can feel its effect to some extent, and water vapor in the atmosphere is a very important factor in weather and climate.

In the liquid state, the individual molecules have less energy, and some bonds form, break, then re-form. At the surface of liquid water, molecules are continually moving back and forth from the liquid state to the vapor state. At a given temperature, there will be an equilibrium between the number of molecules leaving the liquid, and the number of molecules returning.

In solid water--ice--the molecules are locked together in a crystal structure: a framework. They are not moving around, and they contain less energy.waterbowl.gif (2008 bytes)

How do you make water evaporate? Here is a bowl of water. Make the water evaporate. Go ahead.

How did you make the water evaporate? Probably you added heat. You might have set it out in the sun, or possibly put it over a fire. To make water evaporate, you put energy into it. The individual molecules in the water absorb that energy, and get so energetic that they break the hydrogen bonds connecting them to other water molecules. They become molecules of water vapor. Evaporation is the change of state from liquid to vapor. In the process of evaporation, the molecule absorbs energy. This energy is latent heat. Latent means hidden, so latent heat is "hidden" in the water molecule--we can't feel it, but it is there. Wherever that individual molecule of water vapor goes, it takes that latent heat with it. To get the molecule of water vapor to become liquid again, we have to take the energy away, that is, we have to cool it down so that it condenses (condensation is the change from the vapor state to the liquid state). When water condenses, it releases latent heat.iceblk2.gif (1894 bytes)

Now, how do you make ice melt? Here is a block of ice, water in the solid state. Make it melt. Go ahead.

Again, you probably melted the ice by adding energy. The additional energy was absorbed by the individual molecules of water, which became so energetic that they broke some of the hydrogen bonds holding the ice crystal together, and became liquid (that is, the ice melted). This energy is also latent heat, and each molecule of the liquid water is holding that latent heat. To change the liquid water back to ice, you have to take that latent heat away, or in other words, cool the water.

Water could change directly from the frozen state to the vapor state without passing through the liquid state first. This process is called sublimation. Water can also change from the vapor state to the frozen state without passing through the liquid state. This is usually called deposition, and is what you see when frost forms on grass or windows on a cold night. (Sometimes the term sublimation is used when water changes state in either direction, that is, from solid to vapor, or vapor to solid).

The really important thing to remember is that each time water changes state, energy is absorbed or released. This energy is latent heat. Latent heat is the energy absorbed or released when a substance changes its physical state. Latent heat is absorbed upon evaporation, and released upon condensation to liquid (as in clouds). Latent heat is also absorbed when water melts, and released when it freezes.

How much heat does it take to get water to change state? If the water is at a temperature of 100 degrees C (that is, the boiling point, or 212 degrees F) it takes an additional 540 calories of heat to convert one gram of water from the liquid state to the vapor state. When the vapor converts to the liquid state, 540 calories of energy will be released per gram of water. If you are converting solid water (ice) to liquid water at 0 degrees C, it will require about 80 calories of heat to melt one gram of ice, and the 80 calories will be released when the liquid water is frozen to the solid state.


waterstaterev.gif (12130 bytes)

Water does not have to be at the boiling point to evaporate. If you don't believe this, set a pan of water out in the sun and watch it slowly disappear. The sun's heat is not boiling the water, but it is evaporating it. In a given amount of water at a given temperature, some molecules of water will have more energy than others, so some molecules will be able to evaporate, while others remain in the liquid state. The lower the temperature of the water, the more energy is required for evaporation. If the water is liquid at a temperature of 0 degrees C, the latent heat of vaporization is 597 cal/g, compared to 540 cal/g at 100 degrees C. In between, at 50 degrees C, an input of 569 cal/g would be required for evaporation.

It will take a total of about 720 calories per gram to sublimate water, that is change it directly from ice at 0 degrees C, to vapor at 100 degrees C: this includes 80 calories from latent heat of fusion (melting) + 100 calories to raise the temperature of the water 100 degrees C + 540 calories to make the liquid water evaporate (latent heat of vaporization). Similarly, about 720 calories per gram will be released when water is changed directly from vapor to ice, the process called deposition.

Answer 2

This is because steam at 100 deg C contains more heat than water at the same temperature. It contains 540 cal/g more heat. This value is the latent heat of vaporisation (heat required to convert 1 g of water at 100 deg C to steam at 100 deg C, or in other words, simply to change the physical state).

Answer 3

Steam contains the latent heat of vaporization and can move about (can't remember if its 540 or 1000) times as much heat per pound or gram or whatever. It also has a heat transfer factor that's much higher maybe 6 times or up to 20 times.

Answer 4

let us cosider this question in two ways
1. water at 100 degree celsius cointains heat which is given by the formula Q=MSt where t is rise in tempratuer,s is specific heat ,m is mass of water
2. steam on the other hand contains heat given by the formula Q= MSt+ML where L is latent heat of fusion whose value for 1g water is 540 cal
so clearly steam at 100 cointains more heat than water at 100. for this reason steam is a better agent than water. as from principle of calorimetery we know heat lost by hot body = heat gained by cold body & more is the heat cointained more will be the heat lost

Answer 5

because the latent heat of boiling of water is very high. ie the water at 100Cel need some more heat energy to break the inter moleculat force of attraction and become a water vapour. htat is called the latent heat .

Answer 6

Simply put, it is because steam contains more energy.

It contains the energy needed to increase the temperature of liquid water to its boiling point of 100 Celsius and the energy to change the phase of water from liquid to gas.

Boiling water only has the first.