You know when kids tell you some simple facts that you agree with and then a question which seems to contradict everything you have just told them?
Here are my facts and question of the day.
Water is solid up until 0 degrees when it becomes liquid. This is called melting.
Water is liquid from 0 degrees up to 100 degrees when it becomes gas. This is called boiling.
Water is gas above 100 degrees and this is called steam.
So how does my pond water evaporate without boiling the fish?
Evaporation doesn't need to occur at boiling.
DrP
In evaporation (pond in this example) the particles leave the water from its surface only = Slow.
In boiling (kettle) the bubbles of gas form throughout the liquid. They rise to the surface and escape to the surroundings, forming a gas = Rapid.
Neither of those answers are actually proper answers.
When the evaporation happens, is the water ice, water or steam?
If it leaves slowly, is it still gass, if not how does the water float in the air suddenly?
In a liquid the particles are moving around at the surface a few can"jump out" this is evaporation. When the liquid iss heated the particles move around faster so more can "jump out" at 100°C in water loads are doing this-boiling.
First person to mention water vapour then has to explain if that is ice, water or gas or why have you invented a new catagory of being.*
*She was a know it all 6 year old
Just stick her in front of YT and let that answer those questions!
When the evaporation happens, is the water ice, water or steam?
Water is always water regardless of state.
Water vapour does not need to be at 100°C. It's just most of the water will still be liquid.
anagallis_arvensis - Better explanation and is what I said but I made the mistake of mentioning water vapour.
So these jumping particles become water gas? So does that mean water goes from liquid to gas before boiling point? Why do people keep saying it is boiling point then?
Q5 is plain wrong. Boiled water is boiled water. Distilled water is condensed from the atmosphere.
If you have a dehumidifier you can demostrate, or just take something out of the freezer and watch it get wet.
I thought that water that evaporated is not in gaseous state - its liquid molecules suspended in the air. To be gaseous it needs to be over 100C ?????
First person to mention water vapour then has to explain if that is ice, water or gas or why have you invented a new catagory of being
Water vapour is water as is ice. Water vapour is also a gas.
Solid, liquid and gas are states of matter
Ice is solid water, water vapour is gaseous water and in its liquid form water is just referred to as water which is the confusing bit. Steam is hot water vapour.
First person to mention water vapour then has to explain if that is ice, water or gas or why have you invented a new catagory of being
I guess that is the point it all does it.
Because when the water evaporates it cools the pond. I'd be more worried about them freezing.
Evaporation of water happens at a range of temperatures. It also depends on pressure. Water at the top of mountain boils at a lower temperature than see level.
I have no idea how to explain this to a child or if I even understand it well enough to explain simply to anyone.
Evaporation cools things because the faster particles that are leaving the water take their energy with them so the average kinetic energy of the liquid left goes down. Temperature is just a measure of the kinetic energy of the particles.
Clouds are accumulations of liquid water. They're not gaseous.
Evaporation of water happens at a range of temperatures. It also depends on pressure. Water at the top of mountain boils at a lower temperature than see level.
Yeah that's got me stumped 😀
I guess there is less pressure pushing the particles back into the liquid so they need less energy to escape the surface
I’ll try and explain this for a kid, using the fact that I’m watching frank turner at Reading fest on iPlayer to create an analogy.
Your pond is full of liquid water. Liquid water is in fact made of individual molecules of water, and they’re all somewhat inclined to stick together, much like the crowd of people watching frank turner. Most of the frank turner crowd seem pretty chilled out. They’re not hot and bothered. That’s how temperature works - it’s a measure of the average (or overall) energy level of all the individual molecules. But there are a few individuals watching frank turner that are devoted fans and they’re jumping up and down. They are metaphorically ready to evaporate off into the air! The crowd as a whole still seems pretty cool.
but now frank uses his charm to whip up the crowd to all jump along. It’s like he’s lit a fire under the whole arena. When the song kicks in the whole crowd are jumping. Every single molecule is bouncing with energy, it’s like a boiling liquid.
Best without sound but this will push your ability to explain further:
Clouds are accumulations of liquid water. They’re not gaseous.
that’s right, clouds are drops of liquid or solid (ice) water in suspension of air, which brings us to one of my favourite words: aerosol.
Think like an aerosol paint spray can. Drops of paint in air. You get rain once enough tiny drops (another fave word coming up) aglomerate into bigger drops that are heavy enough to fall out of the sky.
It's either Brownian Motion or as DeLaSoul reckoned - 3.
Either answer is acceptable upto Masters Degree level.
WCA, did you do high school physics or chemistry? Sufficient answers were in those to answer these questions.
I was hoping DrP would thrown in a bit more about probability. Then intermolecular bonds maybe a bit of van Der Waal’s force, and then we’d be off to the races!
That gaseous water exists at <100C must be fairly obvious given humidity or condensation on cold windows.
Most exciting water fact is that solid water is not the densest form. It’s densest at about 4Celsius
The water is basically dissolving into the air. So if they are happy with salt into water not being melting that should be ok.
A substance, in this case water, doesn't stay entirely in one state wherever it is on the phase diagram (pressure and temperature). The boiling point and the melting point are where the two phases either side of the boundary are in equilibrium, ie as much ice melts as water freezes. Move either side of that phase boundary either by changing temp or pressure and you no longer have equilibrium so soon have mainly a single phase, ice, liquid or vapour, but molecules are still coming together or moving apart and bits of the substance change state. That state change is evaporation or condensation etc.
I for one would like to hear an explanation of either sublimation or the triple point in terms of a frank turner gig. Beyond my ability that.
Does it show?
Elaboration in case I’m wrong and cause offence: grandparents can escape difficult questions with ice creams. Parents reserve ice creams for the hardest situations or the easiest ways out only when the expected sugar rush can be tolerated. I’m sure you managed either situation expertly wca 🙂
Ok good. If/when I’m a grandparent I’ll just have myself a massive tub of ice cream at my place and a comfy chair. My ***+ kids will have to deal with the rest.
Perfectly deduced. She is indeed my granddaughter which is partly why I was impressed with her telling me about the different states of matter - solid, liquid & gas - so clearly aged 6. Apparently she had been talking to the interesting lady in the tent next to theirs on holiday last week.
I’ll try and explain this for a kid, using the fact that I’m watching frank turner at Reading fest on iPlayer to create an analogy.
Your pond is full of liquid water. Liquid water is in fact made of individual molecules of water, and they’re all somewhat inclined to stick together, much like the crowd of people watching frank turner. Most of the frank turner crowd seem pretty chilled out. They’re not hot and bothered. That’s how temperature works – it’s a measure of the average (or overall) energy level of all the individual molecules. But there are a few individuals watching frank turner that are devoted fans and they’re jumping up and down. They are metaphorically ready to evaporate off into the air! The crowd as a whole still seems pretty cool.
but now frank uses his charm to whip up the crowd to all jump along. It’s like he’s lit a fire under the whole arena. When the song kicks in the whole crowd are jumping. Every single molecule is bouncing with energy, it’s like a boiling liquid.
I still believe
Here's slightly enhanced version the answer I gave my similarly inquisitive 5 year old:
When you add heat to liquid water it speeds up the molecules. Some of that means the temperature of the water goes up (faster molecules = higher temp) and some of them are fast enough to escape as water vapour (evaporate). The more heat you put in the hotter the water will get and the more molecules will escape (hence ponds evaporate in hot weather). Once you get to boiling point any extra heat you put in won't increase the water temperature, it'll just ping more molecules out - the bubbles you see in the liquid have water vapour inside, not air. One of the reasons steam burns are worse than water burns is because steam can be >100 degrees but water can't.
Hope that's useful. It's more or less what I used to teach an S1 class. Not sure if my lad really understands that stuff but he seems to enjoy listening to me talk about science and I'm really chuffed he's asking such questions.
Water evaporates long before reaching 100c...if it didn't puddles would never disappear after rain as it wouldn't dry up.
The temperature measured by a thermometer represents the average energy of the water molecules. The molecules bounce around randomly, exchanging energy as they do. Some will have higher energy, some will have lower energy. Even though the average energy is below the threshold to evaporate, some individual molecules will exceed that threshold and they will evaporate. When they evaporate, they carry energy with them so the temperature of the liquid drops slightly every time a molecule evaporates. When you boil a kettle, you are pumping energy into the liquid and that energy is then removed by the molecules that evaporate. This means that the remaining liquid stays at a constant temperature (i.e. average energy level)
I thought that water that evaporated is not in gaseous state – its liquid molecules suspended in the air.
No, that’s an aerosol.
Seems to me the problem in learning about this is the plethora of names we give water. Water, ice, steam, water vapour - four names for three phases. Confusion is understandable.
<p style="text-align: left;">The temperature of the water is a measure of the average energy of the molecules. Some of them have more energy, they are the ones that jump out of the liquid and become free in the air.</p>
If the air cools down then the water molecules bump into each other and they no longer have enough energy to escape the water bonds and they clump together into little drops of actual water. This is clouds. Cooler still and they clump together into even bigger drops which can no longer float about and they the fall from the sky as rain.
If the ground cools down outside then the water molecules collect on the grass as they lose energy, this is dew. The reason the air molecules don't form droplets is that the attraction between them isn't as strong so even the energy in cool air is enough to stop them clumping together.
The thing about 100C is that's the point at which the average energy of the water molecules is enough to break the bonds.
Temperature is a measure of average kinetic energy. Think if a bell curve some molecules are on the extreme right they have enough energy to escape the surface of the puddle and they will. The shape stays the same so there's always enough energy that some molecules will escape. (Draw a line on the RHS of the curve all molecules above this line can escape. Warming pushes the curve to the right so more molecules are above the line evaporation happens quicker.
The escaping molecules when applied to sweat are taking energy away that's why sweating cools you down.
Should have noticed there was a second page.
I always start energy distribution curves in rates at Higher with "why does a puddle dry up?"
Hydrogen bonding innit. Water should actually be a gas at room temperature but the weak hydrohen bonding affect due to the molecules becoming marginally positively and negatively charged due to the oxygen atoms distorting the orbits of the electrons on the hydrogen.
This is why water is most dense at 4 degrees and expands when it freezes, everything else contracts.
And ice cream.
