Specific heat and latent heat of fusion and vaporization (video) | Khan Academy
What is the specific internal energy of liquid water at 75 o. C and 1 bar? . temperature (as opposed to latent heat, see below). .. Clapeyron equation for this purpose. When ∆ v. H Finally, Watson's correlation can be used to estimate ∆ v. H. Learning Objectives. After this lesson, students will be able to: Define the term ' specific heat capacity' and explain what it means; Explain the difference between . Specific heat capacity and heat of vaporization of water. Evaporative cooling. Why ice floats.
Latent Heat and Freezing and Boiling Points | EARTH Water: Science and Society
We are waiting for the thermometer and the water to reach thermal equilibrium! At thermal equilibrium, the temperature of the thermometer bulb and the water bath will be the same, and there should be no net heat transfer from one object to the other assuming no other loss of heat to the surroundings. Converting between heat and change in temperature How can we measure heat?
Here are some things we know about heat so far: When a system absorbs or loses heat, the average kinetic energy of the molecules will change. Thus, heat transfer results in a change in the system's temperature as long as the system is not undergoing a phase change.
The change in temperature resulting from heat transferred to or from a system depends on how many molecules are in the system. We can use a thermometer to measure the change in a system's temperature. You may have seen this for yourself if you've ever put a sealed glass container containing a mostly-watery food soup, soda, etc. With most other liquids, solidification—which occurs when the temperature drops and kinetic motion energy of molecules is reduced—allows molecules to pack more tightly than in liquid form, giving the solid a greater density than the liquid.
Water is an anomaly that is, a weird standout in its lower density as a solid. Left Crystal structure of ice, with water molecules held in a regular 3D structure by hydrogen bonds. Right Image of icebergs floating on the surface of the ocean. Because it is less dense, ice floats on the surface of liquid water, as we see for an iceberg or the ice cubes in a glass of iced tea.
Specific heat, heat of vaporization, and density of water
In lakes and ponds, a layer of ice forms on top of the liquid water, creating an insulating barrier that protects the animals and plant life in the pond below from freezing. Why is it harmful for living things to freeze? We can understand this by thinking back to the case of a bottle of soda pop cracking in the freezer. When a cell freezes, its watery contents expand and its membrane just like the soda bottle is broken into pieces.
Heat capacity of water It takes a lot of heat to increase the temperature of liquid water because some of the heat must be used to break hydrogen bonds between the molecules.
In other words, water has a high specific heat capacity, which is defined as the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius. Like in nutrition information?
This calorie is similar to that one, but not exactly the same. Because of its high heat capacity, water can minimize changes in temperature. For instance, the specific heat capacity of water is about five times greater than that of sand. This is a number similar to the specific heat, but instead of telling you how much heat you have to add in order to change the temperature, this is telling you how much heat you have to add in order to change the phase. And it turns out the latent heat of vaporization for water is huge.
This means it takes 2, joules to turn one kilogram of water, which is at the boiling point, into one kilogram of vapor.
So, if I'm trying to get this water from 20 degrees turned into vapor, first I need to MC delta T, get it to degree Celsius.
And then I need to add to that another amount of heat, an amount of heat M times L. The mass is two kilograms of this water. L for water is 2, So I get that it will takejoules to get the water up to the boiling point, and it will take another 4, joules to turn that water into vapor which in total gives 5, joules in order to get this from 20 all the way up to two kilograms of vapor. Now, there's one more thing that I wanna show you. Let's get rid of this. Let's say instead of starting with water you started with some ice.
Let's say you started with a big piece of ice, three kilograms worth of ice. And it was very cold. This wasn't just at zero.Heat Capacity and Specific Heat - Doc Physics
Let's say this started at an initial temperature of negative 40 degrees Celsius. The question I wanna know how much heat would we have to add in order to turn this three kilogram block of ice into three kilograms of water vapor?
But not just get it to the point of being vapor. I wanna get it to hotter than a degrees Celsius. I wanna get this to a T final of degrees Celsius. How much heat would I have to add in order to do that? And to track this, to visualize this a little better, I'm gonna track what the temperature is on this vertical axis as a function of how much heat we've added into this system.
Let me quickly show you how not to do this. My C is, well, whatever my C is. We'll talk about that in a minute. All right, delta T, my final temperature is degree Celsius. My initial temperature is negative You can't forget the negative sign. And I just plug in my specific heat and I find my value, this is wrong.
You cannot do it this way. For one what specific heat are you gonna put in? The specific heat of water? The specific heat of ice? The specific heat of vapor? They all have different specific heats.
And for two there's gonna be phase changes. First the ice turns into water and then at some later point the water turns into vapor. You can't just neglect and gloss over those phase changes. So this is not how you do it. Here's what you should do. We're gonna start at negative 40 degrees Celsius. I know this is above the axis over here but just pretend like this isn't the zero point for this vertical axis.
And we're gonna add heat and that's gonna bring this temperature up to zero degrees Celsius, and we have to stop there.
We have to pause at zero degrees Celsius because we have to pause every time there's gonna be a phase change. So how much heat does this correspond to right here?
We can use MC delta T. M is three kilograms. The specific heat of ice is about 2, and the final temperature is zero, our initial temperature, so T final minus our initial is negative Don't forget that negative sign. And if you calculate that you get that amount of heat. But that's just getting the ice up to the melting point.
Now we need to melt it.
Specific Heat and Latent Heat
What's this graph gonna look like while it melts? Well the temperature of the ice is gonna stay constant while this thing melts. As you're melting the ice cube the temperature doesn't change. All that energy is going into breaking those bonds and turning this ice into water. So, how much heat does this correspond to? It's a phase change so you gotta use Q equals ML.
The M is three kilograms. The latent heat, we can't use the latent heat of vaporization. This is a solid turning into a liquid. That's latent heat of fusion that we need, and the latent heat of fusion for water is aboutjoules per kilogram which gives youjoules of heat in order to turn this ice at zero degree Celsius into water at zero degrees Celsius. Now you see how this works. We've got to take this water at zero up to what?
Not up to Up to degrees Celsius because that's where it's gonna turn into steam. And whenever there's a phase change you gotta pause because your specific heat is gonna change its value.
So this Q that is required right here we can do MC delta T, specific heat of water is 4, Delta T is, final isinitial is zero. We get 1, joules. Now we've got to turn that water into steam. How much heat is that gonna take?