- LeBron Asks: Why does sweating cool you down?
- Evaporative cooling
- Heat of vaporization of water and ethanol
- Specific heat of water
- Liquid water denser than solid water (ice)
- Specific heat, heat of vaporization, and density of water
- Temperature and state changes in water
Water less dense as ice. Why lakes don't freeze solid.
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- He said that if the water loses energy the molecules cant get close to each other so the density decreases as it becomes solid. Wouldn't that apply to all other substances?(22 votes)
- It's because of the crystal lattice structure - the patterns that the molecules/ions bind together into as they become solid. A lot of substances have a tight 'cubic' structure, and get pulled tighter together as they lose kinetic energy, but because of the water molecule's 'bent' shape and the angle of its slightly positive/slightly negative ends, they form a lattice with a lot more space in between.(49 votes)
- Hi! The other elements in liquid form have bonds allow them to get closer to each other or let them bumping into each other which gives them liquid properties of matter. What is happening when they get in to solid state and why they become more denser then liquid form? When we compare them with water molecules, they have also kinetic energy, they have attractions. I did not get the difference between hydrogen bonds and the other intermolecular forces which causes this difference of water.(14 votes)
- Good question! The liquid state in many other substances is caused by the fact that their molecules have more kinetic energy and want to spread out and flow AWAY from each other. When they become cold, they freeze to a more dense solid state because their molecules lack the kinetic energy to drift away from each other and flow, so they get stuck close together. In water, the hydrogen bonds are actually causing the water molecules to be attracted to each other, so when they have kinetic energy and can flow, they want to flow CLOSE to and right past other water molecules. When water freezes, its molecules lose energy and get stuck in a lattice structure in which they are farther apart from each other than in their liquid state, thus making ice less dense than water. The water molecules' low energy in their solid state prevents them from fulfilling the attraction of the hydrogen bonds and moving close to each other. Hope that was helpful! :)(21 votes)
- Water instantly freezing
I have had this happen to me on several occasions but I am unable to find an explanation.
The scenario takes place in Afghanistan at 2200m/7021'; weather is winter but warm during the day. There is snow on the ground but it does re-freeze at night. The situation happens at about midnight:
"I get up for my nightly duties and on my way to a heated shack I pick up a 20 ounce bottle of water that has been stored outside. This water was exposed to the daily sun and then also to the cool air at night. The bottle of water is sealed and in its liquid state when I pick it up. It didn't matter if I opened it then or when I arrived in the heated shack, but as soon as I opened it the entire liquid (water) contents would freeze. The water would freeze as soon as I broke the seal on the bottle. I have had it happen slower over a couple of minutes too."
What is going on and why does it freeze only after I open the bottle?
- So is it true that if ice wasn't less dense than water, a lot of life as we know it would be different? It seems incredibly lucky that water is one of the most common molecules in the universe...(8 votes)
- Yes! The unique properties of water allow for the existence of life on earth. If ice were denser than water, bodies of water would freeze bottom first, killing all of the animals that normally dwell under the ice.(8 votes)
- I don't get why the lake would freeze solid if the ice sank. It seems to me that the total of energy transfers between the water and its surroundings would still remain the same; wouldn't the sunken ice melt due to the contact with the (relatively warmer) bottom of the lake?
And how does the lower density of ice prevent the lake from completely freezing from top to bottom?(2 votes)
- Ice is a thermal insulator, whereas liquid water is not. So, the floating ice prevents the deeper water from losing enough energy to freeze.(8 votes)
- What other substances are more dense in the liquid state than the solid state?(4 votes)
- According to wikipedia, other substances that expand on freezing are silicon, gallium, germanium, antimony, bismuth, plutonium and also chemical compounds that form spacious crystal lattices with tetrahedral coordination.SiO2 also shows this property.(4 votes)
- Is it possible for an electron from 1 water molecule to jump to another water molecule causing H2O- and H2O+ to form?(5 votes)
- Why does the heat in the water not melt the ice?(2 votes)
- I understand that because of hydrogen bonding, the water molecules becomes less dense; however, how come the same isn't for other elements that go from liquid to solid? What makes those elements increase is density as they go from liquid to solid? Basically, what about hydrogen bonding is so unique to make water less dense when in solid form?(3 votes)
- When water is in a liquid form, then the water molecules move around because the temperature is fairly warm in a room environment. When the water molecules move around, then the maximum amount of hydrogen bonds possible in that mass of water has not been reached because there are always a few water molecules in motion. When water freezes, then molecules have to settle down because they can't move around at a cold temperature. Since so many molecules aren't moving, they quickly form hydrogen bonds wherever they are. If you look at several water molecules, the hydrogen bonds have huge gaps, and holes between each other. Since more hydrogen bonds are formed when water freezes: More holes and gaps are formed which decreases the density of ice.(2 votes)
- Why do hydrogen bonds need gaps between O and H?(3 votes)
- [Voiceover] If you look at most substances, so this is most things, right over here. As we go from a liquid state where things are literally fluid, the molecules are moving past each other, to a solid state, where things are rigid or more rigid, you typically have something getting more dense. So the liquid state would be less dense. Less dense. And the solid state would be more dense. Would be more dense. Let's think about what would happen if water were like most things here. So imagine a body of water. So let's say that's the land right over here, this is a cross section of a body of, I don't wanna draw brown water, I wanna do blue water. So this is a cross section of body of water, like say, we see in this picture here. Now let's say it is very cold. That the air is extremely cold. Let's say it's below the freezing temperature of water. Well what would happen is the water up here would freeze. And this is actually what does happen. Water at the surface would freeze, but if this ice were more dense, the solid water were more dense than the liquid water, well then the ice would sink. The ice would sink and collect at the bottom. The ice would collect at the bottom right over here. And then the water over here would freeze again. It would freeze again. But if that were more dense, then it would sink and collect at the bottom. And you keep going with this process on and on and on, and eventually the entire body of water, the entire lake would freeze solid. Would freeze... It would freeze solid. Now you can imagine this wouldn't be that good for the animals that are living in the water. If you imagine some fish in here. Those fish would then freeze. And most living things, there are a few simple organisms that can survive being frozen. But most living things would just die. And so this would not be a good environment for animals to live in, or for even biology to take place. But what's neat about water, it does not follow this pattern. When we're talking about water, when we're talking about water, when we go to the liquid state, when we go from liquid water to solid ice, to solid ice, we actually get, we actually get less dense. So this right over here is less dense. This is why ice floats. This is more dense, more dense. And this is less dense. And to think about why that is, it all goes back to the hydrogen bonding. So we've seen in previous videos. So, I'm gonna do it all in one color. Oxygen, hydrogen, hydrogen. Let's say this is the liquid state that I'm drawing right over here. This is liquid water. Liquid water. So then you have oxygen, and you have oxygen and hydrogen and hydrogen. And you have oxygen and hydrogen and hydrogen. We've already talked multiple times about the fact that you have partial negative charges at the side away from the hydrogens. Partial negative, partial negative because oxygen is so electro-negative. And you have partial positive charges on the hydrogen ends. Partial positive charges at the hydrogens and these partial negatives and partial positives attract each other and this is called hydrogen bonding. Now the liquid state, you have enough energy. The temperature is just really average kinetic energy that these molecules are able to bounce around and flow past each other. These hydrogen bonds get broken and get reformed over and over again. These things flow past each other and also they have enough energy to kind of push even closer to each other than even the hydrogen bonds would dictate. Sometimes they go closer, sometimes they're further, sometimes they're pushing around. But as we get-- As we get cooler, as we get cooler and we lose heat, then they don't have the kinetic energy to kind of-- They get closer and bump up against each other and move right and flow right past each other and they form a lattice structure where it will look more like this. Where it will look like oxygen, hydrogen, hydrogen, oxygen, hydrogen, hydrogen, oxygen, hydrogen, hydrogen. And so you actually have the molecules being further apart from each other because they don't have the kinetic energy, once again, to keep breaking and reforming these hydrogen bonds, or even to kind of have the kinetic energy to push up against each other. And so you form this lattice structure. You could even have another oxygen. And I'm obviously drawing it in two dimensions, but ice, things in our universe, in our reality are three dimensions. But hopefully this gives you the big picture of it. Oxygen, hydrogen, hydrogen. And so you have these hydrogen bonds. I wanted to do those in white. These hydrogen bonds. And remember, these hydrogen bonds, they're still, it's still the case, electrons are still moving around, and so you still have a partial positive charge here and partial negative charge there, but there's not enough kinetic energy to push them close to each other and flow past each other and so you have ice right over here. You have solid water. You have ice over here being less dense. And this is what keeps ice floating, this is what keeps icebergs floating, this is what keeps lakes like this from freezing solid. This is why the surface freezes, but you have water below it. In fact, that ice on the top protects the water below from... You can imagine, the ice, it protects it from getting even further frozen and so you have animals able to just hang out. Hang out down here and go through the winter and then everything will thaw once you get to the spring and the summer.