Why does steam at 100c

What your temperature sensors perceive mostly depends of the amount of water. The steam that forms above pots or kettles with boiling water and anything else that is colloquially called steam is a mixture of gaseous water, air, and liquid water droplets. The latter is what you can actually see; pure gaseous water is transparent. Instead, if you boil a kettle of water, the steam that comes out has already considerably cooled down due to contact with the air and other factors.

It can still cause severe burns though. In general, your temperature perception depends on the amount of heat deposited on a timescale relevant to your heat sensors. This in turn depends on:. Rather it has the temperature of the surrounding air.

You can think of it as water dissolved in air. It exists at all temperatures and causes or rather is humidity. The amount of water you can dissolve in air depends on the temperature.

Now due to changes in temperature, it can happen that a portion of air has more water dissolved in it than it can hold. In that case, the water condenses to droplets you see as steam, clouds, or fog — not there is a fundamental difference between those. The heating also causes an upward flux of air, which carries those droplets with it and avoids them returning to the water immediately. Both, boiling water and hot steam are pretty dangerous and how dangerous exactly depends on how long you are exposed to how much of it at what temperature and more.

As one is a liquid and one is mostly a gas, encounters with them are not directly comparable as opposed for example to putting your arm in two different liquids. You might as well ponder whether a gorilla would win a fight against a shark. We might look at how much reported injuries we get for either, but that says more about how careless people are around the respective substances.

What we define as "hot" or "cold" is the transfer of energy -- how much quantity and how fast rate of transfer -- and how it raises our temperature. The more energy that is transferred from the object quickly, the hotter the object feels. First, steam is in a vaporized phase -- which is why it has more energy. At Celsius, water can exist both in gaseous and liquid phases. However, to vaporize liquid water, an energy input is required. This energy called vaporization energy is specific to each material, but if added, won't raise the temperature, but will simply vaporize the liquid into a gas.

So, by vaporizing C water, you have water vapor at degrees. Similarly, you can condense this vapor, by removing that same amount of energy required to vaporize it.

In that case, you'd recover water at degrees. When you touch something hot, it will transfer heat to you until the temperatures have equalized. So when you touch hot water, the water will simply transfer whatever energy it needs to reach your hand's surface temperature which won't happen, you'll take your hand out much sooner.

However, when you touch steam, it will also transfer the condensation energy to you -- which is actually a lot of energy. This energy drastically raises your hand's the temperature, and you feel it as "hot.

The higher this constant, the faster heat gets transferred, so more heat gets transferred, and your hand's temperature increases.

As Wrzlprmft points out, steam can more easily enter skin pores. This will ensure more heat is transferred, since the total contact area is greater.

The greater this difference, the greater the heat flow. Note that as heat flows, this difference will shrink. Furthermore, the condensation energy is, for lack of a better word, quite large, which means that a lot will be transferred at that high rate. TLDR: The reason steam feels hotter, is that it can transfer more energy to us faster that is, without decreasing its temperature by transferring condensation energy , whereas water cannot.

Our feeling of what's hot is determined by how much energy and how quickly an object transfers that energy to raise our temperature. Edit: I forgot to mention that unlike water, steam can be packed tightly because it is a gas. Depending on how compressed the steam is in a given volume, you may experience C steam to feel warmer or colder than C water. For the purpose of my answer, I assumed the steam to be dense and tightly packed -- which can eventually make up for steam's lower thermal conductivity constant.

If you were to actually feel both liquid water at C, and true steam not some Water vapor in air at C, then the water will feel hotter.

Note that the stuff that comes out of a kettle is not steam. Note that a sauna is not filled with steam. Because the water will inflict a first-degree burn in 0. But the burn will take almost 30 seconds to progress to third degree, where the pain will stop due to complete destruction of the nerves. Steam, while at the same temperature, will not cool off in contact with your skin. It will remain at C as it converts to liquid, releasing the same energy as cooling the mere water from C to 0C, 4 times over.

A direct steam burn will cause third degree burns within 5 seconds, stopping the pain. Thus, steam "feels" less hot than water, at C. Based on some heat transfer experience, these effects can be quantified fairly easily if we neglect convective heat transfer in the water and steam, and assume that the thermal properties of flesh are about the same as those of liquid water.

Pretty hot. Now for the case of steam at C suddenly brought in contact with flesh at 37 C. Again assuming a constant flesh surface temperature, if we solve Eqn. This exceeds the value for contact with water at C, How hot or cold something feels doesn't purely depend on temperature. Temperature is just an extensive measure of the contained thermal energy amount.

Rather, the important property is thermal conductivity for solids during conduction and the similar heat transfer coefficients for liquids and gases during convection. That is, the ability of the material to deliver the energy to your hand when you touch it. Look up aerogel as an example: while glowing hot thousand of decrees Celsius hot, straight out of the furnace, it can be held in your hand due to its very low thermal conductivity.

Steam does contain more energy than water when both are at the same temperature. Because the steam apart from its thermal energy content also has absorbed latent heat energy for the phase change from liquid to gas. When you touch it, then for both the water and the steam you must absorb enough energy to reduce the temperature to that of your hand. But for the steam you first have to absorb energy to transform it from gas to liquid again.

So you are in total absorbing more energy when touching the steam. If that happens fast - faster than how quick your hand can transfer the energy away from the surface skin - then the temperature of your skin will increase and you might burn.

If feels hotter because though the temperature is the same, it really is "hotter" in the sense of having more heat in it to pour into your skin. Steam burns you thrice over because the process of turning from steam back to water puts out a certain anount of heat into your flesh all by itself without changing temprature. The heat you're adding isn't going into the temprature rising, but the boiling itself.

Check that by timing a pan of water. It will take 5 times as long to steam off a liter of water as it takes to boil it! So when you condense steam onto your hand, every drop releases more than 5 times the energy compared to spilling a drop of water on your hand.

We can nearly say that condensing 1g steam on your hand is like spilling theoretical 'C water on it, because nearly all the dissociation energy of the steam molecules is released as heat when the water atoms coalesce again. I think you've probably confused the question a little. In fact steam can even be hot enough to ignite paper. Note that steam doesn't feel hotter than water as long as you consider steam at degrees which is the case for steam under air pressure, contrary to steam in pressure cooking pans.

The steamy droplets of steam have the same temperature as the boiling water they come from. Maybe a very small amount of latent heat is released. But not enough to make its temperature rise significantly. But even when it did have a higher temperature than water, the steam droplets are too much diluted in the air to do any harm.

If you put your hand in a boiling cup of water you'll probably give a scream. If you enter a s team-filled sauna with an air temperature of degrees Celsius though you will probably not scream if you don't look at the other people. That means that steam when not in motion is a worse conductor of heat than water. It consists of small water droplets but because there are not as much in a unit volume it will not pull much heat out of you.

Only if you blow the steam towards your skin will you give a scream. In that case, all the droplets will meat your skin as one layer of water, causing it to pull the heat out of you. To put it in a nutshell, steam has a much lower heat conductivity than water, which is why steam sucks less heat out of you than water.

Why is steam a worse conductor of heat than water? Air conducts heat very badly, so the net result of both the drops and air steam will be that it's a worse conductor than water. If you would look at the drops only, then obviously it could pull heat out of you. Luckily, the drops are not 1 cm big. This would be hot rain and would surely harm you. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Any answers? Nooks and crannies. Semantic enigmas. The body beautiful. Red tape, white lies. Speculative science. This sceptred isle. Root of all evil. Ethical conundrums. This sporting life. Stage and screen. Birds and the bees. Than how does water from water bodies evaporate to form clouds when temperature on earth doesn't cross even 50 deg.

Think how a puddle of water from a summer rain shower quickly evaporates and disappears as the water is taken back into the atmosphere once the Sun comes out again.

On a colder day the puddle would take longer to evaporate, as less heat from the Sun which drives "The Water Cycle" would mean there was less molecular agitation which facilitates the evaporation process going on? Check out "The Water Cycle" on Wikipedia. It means that the random jostling-about of water molecules in a body of water that's, say, 20 degrees, is just that; random. There's a spread of speed.

If you could measure the speed of every molecule at one instant in time, som would be stationary absolute zero , but others would be temporarily at boiling point. If they happen to "boil" while they are at the surface, they leave the surface, i. That's why a puddle of water will evaporate much faster than the same quantity in a bottle at the same temperature - less surface area to escape from.

Paul Wright, Rochford As I understand it the molecules in water move around as long as it is liquid.