Properties of Water- Thermal - Video Tutorials & Practice Problems
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Properties of Water- Thermal
Video duration:
4m
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Video transcript
In this video we're going to begin our lesson on the thermal properties of water. And so to understand the thermal properties of water we need to understand kinetic energy, and so kinetic energy is really just a measure of energy in the form of motion. And so if substances are moving that means that they have kinetic energy. It's really the energy of motion. Now temperature is a term that we've all heard before in our past, and really temperature is just defined as the average kinetic energy of molecules in a solution or in a sample. And so average here is really the key word. And so if a sample has a really, really high temperature, what that means is that the molecules in that sample have a high average motion. And so notice that these molecules in this sample have large arrows to represent the high average motion that they have, and so they're moving around a lot and very, very fast. Now, low temperature on the other hand, of course, means that the samples, the molecules in that sample have low average motion. And so notice that these molecules have small arrows to represent that they're moving very very slowly in comparison to the high temperature samples. Now, temperature is not to be confused with thermal energy. So once again, temperature is the average kinetic energy. However, thermal energy is the total kinetic energy of molecules that's transferred specifically as heat. And so if we take a look at our image down below over here on the right hand side we can distinguish between temperature and thermal energy. And so notice that we're comparing 2 samples, a hot coffee pot over here on the left hand side with a large swimming pool over here on the right hand side. Now of course the hot coffee pot, if we measure its temperature, it's going to be quite high. It's gonna have a high temperature because the average kinetic energy, in these molecules is really really high, they're moving really really fast over here on average. And of course the swimming pool over here is going to have low temperature. It's gonna be quite cool if you were to jump into that swimming pool, and that's because the molecules on average have low temperature. However, if we focus on the thermal energy, what we'll find is that the hot coffee pot, because it has such a small volume, it actually has a lower thermal energy in comparison to the swimming pool over here, which has a much much larger volume. And so the swimming pool over here is, because it has so many more molecules, the total energy of all of these molecules adds up to be more energy than the molecules over here in the hot coffee pot. And so that means that the swimming pool, simply because it has a much larger volume, has a higher thermal energy. More total energy over here in the swimming pool because it has simply a lot more molecules. And the hot coffee pot, even though on average they have a higher temperature, more motion, total there's a lot lower thermal energy in the hot coffee pot because it has such a small volume in comparison to this large swimming pool. And so this here concludes our introduction to kinetic energy, temperature, and thermal energy and as we move forward in this lesson we'll talk more specifically about waters thermal property. So I'll see you all in our next video.
2
concept
Water’s High Specific Heat
Video duration:
3m
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Video transcript
In this video, we're going to introduce water's high specific heat. And so water's high specific heat really is what allows it to resist temperature changes. Now specific heat is really just defined as the amount of heat energy that's required to either raise or lower one gram of water, just one degree Celsius. And so because water has a high specific heat it means that it takes a relatively high amount of heat in order to either raise or lower 1 gram of water just 1 degree Celsius. And so think about it if you've ever tried to make some pasta first you have to put water into a pot and then you have to put that water in the pot onto a stove. But the water doesn't start boiling immediately once you put that water onto the hot stove. It takes some time, it takes quite a lot of energy in order to heat up that water and raise its temperature. And so this is water's ability to, have a high specific heat and resist temperature changes. And it also works in the opposite way in terms of lowering the temperature of water. It takes a lot to lower the temperature of water. So if you have a water bottle for instance and you throw it into the freezer it doesn't freeze immediately it takes several hours in order to cool down water, until it freezes. And so water has this incredible ability to resist temperature changes because it has such a high specific heat. Now resisting temperature changes is really, really critical for life to maintain homeostasis. Because once again, the temperatures of the environment are constantly going to be changing, some days it'll be hot, other days it'll be really cold. And so life needs to have this ability to maintain homeostasis, maintain an internal set of conditions. And because the cells are made up of a lot of water, they are able to resist the temperature changes and maintain constant temperatures inside the cell despite the fact that the outside of the cell is constantly changing. And so down below we're showing you an example of water's high specific heat. So notice we have this beaker here that's filled up with water and we're applying some heat here, a flame to the water to heat it up. But notice that the water here isn't really impressed by the amount of heat and it's saying, is that all you got? Bring on the heat. It's gonna take a lot more heat to, raise my temperature than just a little flame here. And so that is just this idea that water has a high specific heat. It takes a lot of energy to raise or lower 1 gram of water, 1 degree Celsius and that is what allows water to resist temperature changes. And so this here concludes our introduction to water's high specific heat and we'll be able to get some practice applying these concepts moving forward in our course. So I'll see you all in our next video.
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Problem
Problem
Which of the following is due to the high specific heat of water?
a) Oil does not mix with water.
b) A lake heats up more slowly than the surrounding environment.
c) The high surface tension of water.
d) Sugar dissolves in hot tea faster than in iced tea.
A
Oil does not mix with water.
B
A lake heats up more slowly than the surrounding environment.
C
The high surface tension of water.
D
Sugar dissolves in hot tea faster than in iced tea.
4
concept
Water’s High Heat of Vaporization
Video duration:
3m
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Video transcript
So in addition to water's high specific heat that we talked about in our previous lesson video, water also has a high heat of vaporization. And so vaporization or evaporation is really just referring to the phase transition from a liquid state to a gaseous state or in other words, the phase transition from a liquid to a gas. Now, the heat of vaporization is a term referring to the amount of heat required to convert exactly 1 gram of liquid to a gaseous state. Now, once again, water has a relatively high heat of vaporization which means that it takes, quite a lot of energy to convert 1 gram of liquid water into a gaseous state. And the reason that water has such a high heat of vaporization is due to the abundance of hydrogen bonds that form in the liquid state of water. And so if we take a look at our image down below we can get a better understanding of this heat of vaporization. And so notice in this image we're showing you a pot of boiling water where the liquid water is being converted into a gaseous state. And so when we zoom into the liquid water and look at the water molecules here, notice that between each of these water molecules are an abundant of hydrogen bonds forming between them. And so there are lots and lots of hydrogen bonds in the liquid state of water. However, if we apply high amounts of energy and high amounts of heat like what this fire beneath this pot is doing, then each of these hydrogen bonds between the water molecules can be broken. And when these hydrogen bonds are broken, the water molecules are able to escape from the liquid water into its gaseous form. And so that's what we're showing you above is a zoom in into the steam and the water vapor. And so notice that there are no hydrogen bonds between the water molecules in this steam or gaseous form. And so once again water has a high heat of vaporization which means it takes a lot of energy to convert liquid water into its gaseous form. And many of you may be familiar with this idea in your own perhaps for making pasta. When you put the pot of water initially onto the stove, the water does not boil immediately. In fact, it takes quite a lot of time, a lot of heat and a lot of energy to convert the liquid water into the gaseous state and so that fact that it takes a lot of energy is why water has a high heat of vaporization. And so this here concludes our brief lesson on water's high heat of vaporization and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
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Problem
Problem
Which if the following defines the term evaporation?
a) The conversion of a liquid into a vapor.
b) The conversion of a solid into a vapor.
c) The conversion of a vapor into a liquid.
d) The conversion of a vapor into a solid.
A
The conversion of a liquid into a vapor.
B
The conversion of a solid into a vapor.
C
The conversion of a vapor into a liquid.
D
The conversion of a vapor into a solid.
6
Problem
Problem
Choose the correct statement: Liquid water ________.
a) Is less dense than ice.
b) Has a lower specific heat than most other molecules.
c) Has a higher heat of vaporization than most other molecules.
d) Is nonpolar.
A
Is less dense than ice.
B
Has a lower specific heat than most other molecules.
C
Has a higher heat of vaporization than most other molecules.