3. Water
Properties of Water- Density
1
concept
Density of Liquid Water vs. Solid Ice
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in this video, we're going to continue to talk about the properties of water, specifically its density and comparing the density of liquid water to solid ice. And so liquid water molecules are really highly packed together, meaning that they have a high density. And they're constantly forming and breaking hydrogen bonds, whereas solid water molecules and the ice form are much less packed, and that means that they are less dense. And this is because solid water molecules actually expand. And this is because they form very stable hydrogen bonds and a lattice structure. And the lattice structure is what allows the water molecules to expand. Now. This is important because solid ice is actually going to have a much lower density than liquid water, and things that have a lower density in liquids are going to float. And so this means that solid ice is going to float in liquid water. And this is incredibly important for life because it means that water is going to freeze from the top to the bottom, and so when it freezes from top to bottom, it creates a layer of ice on the top, and that layer of ice on the top is capable of insulating the liquid water that is below the surface, and this is incredibly important to sustain life. And so if we take a look at our image down below, notice that we're showing you an example of how density of liquid water compares to solid ice. And so over here we have an image that shows you both solid ice up here, the top floating on top of the liquid water that is down below. And so what you'll notice is that if we zoom into the liquid water down below, notice that the water molecules are really highly packed into this little small area. And so the liquid water molecules are really highly dense test because they're so highly packed and these liquid water molecules they're constantly forming and breaking H bonds or hydrogen bonds are constantly breaking and reforming. Whereas if we zoom in specifically to the ice here that's floating on top, notice that it's water molecules are in a lattice structure, and they are much less pack there, much less dense and so solid ice is going to be less dense and because it's less dense, this is what allows it to float on top of the liquid water that's down below, and so it's less dense because it forms stable hydrogen bonds and a lot of structure instead of forming hydrogen bonds that constantly break and reform. And so once again, this is really important because water will freeze from top to bottom. And so the ice layer that freezes on top is capable of insulating the liquid water down below. And that consist, ain life especially imagine? Uh, in the past millions of years ago, our planet went through extreme temperature fluctuations, and there were ice ages that existed, and during the Ice Ages, our oceans would have frozen completely solid if it were not for this amazing ability for water to freeze from top to bottom. Create an insulating layer that keeps the liquid water down below in a liquid form, allowing life to survive those ice ages. And so this is really, really important. And so this year concludes our lesson on the density of water, comparing liquid water density to solid ice density, and we'll be able to get some practice as we move forward in our course. So I'll see you all in our next video
2
example
Properties of Water- Density Example 1
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all right. So here we have an example Problem that's asking, Why does ice float in liquid water? And we've got these four potential answer options down below. Now, after reading through some of these answer options, there are a few that we can eliminate right off the bed, such as Option C here, which says that the Ionic bonds between the molecules and ice prevent the ice from sinking. But of course, we know that water is not an ion because it does not have full charges. It only has partial charges, so it's not in I am, which means that it cannot form Ionic bonds. And so because it says Ionic Bonds here, we should have been able to eliminate answer option C right away. Now answer. Option D here says the latticed structure of ice causes it to beam or dense than liquid water. But once again recall from our last lesson video that solid ice is actually less dense, not mawr dense than liquid water. And so, for this reason, right here, we can eliminate answer option D. So now we're between either option a or Option B and noticed Option A says the high surface tension of liquid water makes the ice float. But even ice that penetrates the liquid surface and goes beyond the surface tension. It breaks the surface tension that ice that breaks the surface tension will still ultimately end up floating once again. So it's not the surface tension that's allowing ice to float. And so option A. Although it might be tempting answer option is not going to be true. And so the real reason that ice floats on liquid water is because stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water. And so because water molecules of ice are farther apart, it means that it is less dense. Solid ice is less dense than liquid water molecules, which are more dense, and so things that are less dense will float. And so Option B is going to be the correct answer for this example problem, and that concludes this example. So I'll see you all in our next video
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Problem
ProblemSolid substances are normally more dense than liquid substances. However, solid ice is LESS dense than liquid water. Why is this characteristic of solid ice important for life?
a) This characteristic allows lakes to freeze solid.
b) This characteristic allows the surface water of lakes to freeze.
c) This characteristic ensures that salt water does not freeze.
d) This characteristic is not important for life.
A
This characteristic allows lakes to freeze solid.
B
This characteristic allows the surface water of lakes to freeze.
C
This characteristic ensures that salt water does not freeze.
D
This characteristic is not important for life.