Specific heat and latent leat of fusion and vaporization | Chemistry | Khan Academy

Let's get out of the special heat and Let's talk about the heat of melting and boiling. Let's say you have a container full of liquid and want to increase the temperature, will probably add heat. But how much heat do you need to add? There is a formula for this. Let's see what's going on here. It will depend on different things. First, how much is the temperature depends on what you want to increase. That is how much the temperature Want to increase? The more you want to increase you need to add a lot of heat. It also depends on how much material you have. In other words, from the mass of the liquid here. The more, the more to raise the temperature need a lot of heat. And it depends on one thing, from the specific heat capacity of a given material. Heat some materials from others more difficult.

And if the specific heat capacity of the material If high, to increase the temperature more coul heat will be needed. Let's be more specific. Suppose our math is water and its temperature is 20 degrees Celsius. Let's say a big pot There are two kilograms of water in it. Special heat capacity, you can look at them or the data. It turns out that the specific heat capacity of water 4186 coul section kilogram degrees Celsius.

And these units are special creates an idea about heat capacity. He says that if a kilogram of water is 1 degree Celsius 4186 coul energy is needed to heat. That's what you already say you need as much heat as you can. Water has a very high specific heat capacity. It is great without raising the temperature too much can hold a certain amount of energy. And let's say the question is from us raise the temperature to 50 degrees Celsius they want. How much to reach 50 degrees Celsius need to add heat? Well, we can come here. We need to find the heat we need to add, weight is 2 kilograms, that is, a special heat capacity of 2 kilograms, he is also 4186, tap temperature change. This also means that T is the initial output of the last T.

So what does the last T equal? T is the last 50 degrees Celsius, we want to get here, The output initially started with 20 degrees Celsius. Now we can find it by the amount of heat. And if you hit it all You will receive 251160 coul. Water temperature 30 degrees This is a very large energy to increase. Therefore, we use water mainly as a heat sink. A lot of heat can be given to the water and the temperature does not change much.

But this example is very simple. Let's look at the more difficult. Let's say you heat the cube from below rather than heating we just take hot metal. Suppose we have 0.5 kilograms of copper and we put it in the water. We preheated the copper and now we put it in the same bowl of water. And we want to know what they are will reach equilibrium temperature? Copper will cool and water will heat. Then when they reach the same temperature there will be a balance. What temperature is this? Well, we need to know a few things. I have already given the mass of copper. We need an initial temperature, initial temperature of copper.

I said we overheated it. Suppose it is 90 degrees Celsius. We also need to know the specific heat capacity of copper and its specific heat capacity is 387. And let's say the initial properties of water has. It was two pounds. The specific heat capacity of water always remains 4186. And let's say it's a temperature of 20 degrees Celsius starts with. That is, we know the equilibrium temperature, the equilibrium temperature at which they will reach about 20 to 90. We need to find out exactly what it will be. And the trick we will use here copper heat loss, and water is heat gain, How do we compare these temperatures? That the heat is not lost assuming they will be the same. We believe that heat is not lost, that is, you want him to occur on the calorimeter, indoors, in an environment that prevents heat from escaping. If the heat is not lost at this time, the heat received by the water will be equal to the heat lost by the copper. In essence, the heat from copper zero will be taken if you collect the heat added to the water, because one of them will be negative, the other is positive and their modulus will be equal.

How do we find them? We have a formula. I remembered that Q is equal to mc delta t, remember that I want it because it's like MCAT, i.e. mc, this delta resembles Aa, The total Q is equal to MCAT. Now I have to use a mass of copper, The weight of copper was 0.5 kilograms, hit 387 with a specific heat capacity tap temperature difference. I do not know the final temperature, this is normal. I will name this variable that I left blank. Let's end it with T I'll call it first. Started at 90 degrees Celsius, that is, let's go 90 degrees Celsius, plus heat from water, we use the same MCAT formula for this.

It weighs 2 kilograms The specific heat capacity is 4186. T end, I still don't know the T end, but I know the original Ti, The initial temperature is 20 degrees Celsius. And I make this expression zero. Our space has narrowed. I'm sorry. It looks a little scary now, you have a great formula. The unknown is hiding here. Can we solve it? Yes, we can. Look, you just have an unknown. The unknown T is the end. These are the same variables. This temperature is water and copper is the temperature to be reached. The whole expression here, the orange expression will give a negative assessment, because copper loses a certain amount of energy and the expression of water is positive, because it gains heat. Both will be corrected. And it gives you zero.

This is what we need. We just need to find the end of T, we hit them for that, T combines the last variables We find the end of t. First I will knock everything open. I will combine the last terms of t and T will calculate the non-final expression. So I will separate the expressions. I try to find the end of T and get 21.58 degrees Celsius. When you look at it, you can say that we did something wrong. 21.58? Water started with 20. The temperature almost did not rise. Yes, that's what we said, the specific heat capacity of water is very high, you can add a lot of heat and the temperature will not change much. Consider that we could add this dish as well. This pot also absorbs some heat, that is, we may have another expression here, Q of the vessel and if we take this into account, or we could throw another cube here and one here.

If you collect all the incoming Qs the heat you gain or lose if you added you would get zero, because if the heat is not lost, that heat will be transferred here. No heat will be generated or lost. Simply contact materials will be transferred inside. This was also the key to resolving the issues, for special heat capacity issues of this type. That's how you set it up and then you found the unknown. In this case, T is the end. Sometimes a variable that is not given to you one of them may have a mass, or the specific heat capacity of one, find the answer without making a difference. Let me ask you another question. Suppose we take the same amount of water, At 2 pounds and 20 degrees Celsius, but this time i want to know that to boil and evaporate all the water here how much heat should I add? Well, the first thing we have to do is to find the boiling point.

And the boiling point of water It is 10 degrees Celsius. With the Q MCAT formula, MC is written with delta T. The mass is 2. The specific heat capacity of the water is 4186. Temperature change, good boiling point is 100, that is, I increase the water temperature from 20 to 100. T is equal to the last 100. T initially to 20. And I know the boiling point must add heat to reach, 669760. I do not pay attention to the main figures, but this is a calculation. But it is not enough to boil. It's just the temperature of the water It was to raise it to 100 degrees Celsius. Not enough. Bring the water to 100 degrees Celsius if you want, he just stands here. But it does not boil.

We must continue to add heat. How much heat should we add? When the water reaches 100 to evaporate the juice you boil and evaporate you need to know the temperatures. Because we boiled in this case because evaporation heat is needed we evaporate the liquid. If we turned a liquid into a solid we would call the heat of melting. Formula for melting and evaporation temperatures looks like it. Q is needed to change the state of the aggregate which is the amount of heat. This happens when the state of the unit changes, melting and evaporation temperatures. Specific heating temperature occurs when changing.

This is the calculated temperature To increase to 80 degrees Celsius indicates how much heat is needed. This calculation will tell us that When you are at 100 how much heat we need to add Let's turn the aggregate state of water from liquid to vapor. Melting and boiling temperatures The formula is similar. Q is equal to mL. m is the mass. The more mass, the more heat you need to add. L is the specific heat of melting and boiling. This term is similar to the specific heat capacity, but you have to change the temperature instead of showing how much heat is needed how much you need to change the state of the aggregate indicates that heat is needed. And it turns out that the boiling point of water the specific heat capacity is very large. 2,260,000 coul kilograms per kilogram. This means that one kilogram of water boiling point To convert 1 kilogram of steam 2 260 000 coul energy needs. So if this juice at 20 degrees if I want to steam first with mc delta T I have to bring it to 100 degrees Celsius.

Then I add a little heat, that is, m multiply by L. It weighs 2 kilograms. L for water is equal to 2 260 000. I get boiling water to bring the temperature Need 669 760 coul and then him to turn the liquid into a seal 4,520,000 coul, this in general 5 189 760 coul gives, that is, 2 kilograms of water at 20 degrees the amount needed to convert to steam. Now I want to show you something. Let's delete it. Instead of starting with water, let's say we start with ice.

Let's say you started with a big piece of ice and 3 pounds of ice. He is very cold. Just not zero. Let's say the initial temperature minus 40 degrees Celsius. Our question is that how much heat should we add 3 pounds of ice 3 pounds turn to steam? But we don't just bring it to the point of evaporation, I want to make it warmer than 100 degrees Celsius. I want the T to end Let it be 160 degrees Celsius.

How much heat to do it should i add To better watch it and bring it to life in our eyes I am typing the temperature on the vertical axis and how much heat by creating a function I will calculate what we need to add. Let me tell you briefly how to do it. In simple terms, Q is equal to mc delta T. m is equal to 3 kilograms. c, c also has a value. We will talk about this for a minute. Delta T. Well, delta T, my final temperature It is 160 degrees Celsius. The initial temperature is minus 40. Remember the negative sign. And I included a special heat capacity I solve the problem, this is wrong. You can't do that. What specific heat capacity should you include? Water? Ice? Steam? Each has a different price. And there are two aggregate changes. First, ice turns into water and then after a while the water evaporates. You can't ignore these aggregate changes. So we do not. That's what you have to do. We start with minus 40 degrees Celsius. I know it's above the arrow, but i don't care the zero point of the vertical line.

And we will add heat to it will reach zero degrees Celsius and we must stop here. We have to stop at zero degrees Celsius, because the state of the aggregate changes every time we must stop. How much heat is this now? We can find mc delta T. m is 3 kilograms. The specific heat capacity of ice is 2090 and the final temperature is zero, our initial temperature, T last exit initial negative 40. Remember the negative sign. We calculate this and find the amount of heat. 250 800 coul. But this was just to bring the ice to the melting point. Now we have to melt it. What will the graph look like when it melts? Ice during melting the temperature will remain constant. When the ice cube melts the temperature does not change. All energy is spent on breaking communications and turn ice into water. How much heat is this? When the state of the aggregate changes, Q is equal to mL.

m is 3 kilograms. Special heat capacity for melting, evaporation we can not use. The solid turns into a liquid. The melt needs a special heat capacity and this heat capacity for water Divide 333,000 couls by a kilogram, This also means that 999,000 coul heat The amount of ice is zero degrees Celsius we can turn sapphire into water. Now you see how it works. Where should we take water from scratch? Not to 160. Here, because 100 degrees Celsius it turns to steam. And we have to stop when the state of the unit changes, because the specific heat capacity will change. To find Q here We can use mc delta T, The specific heat capacity of water is 4186. Delta T, last 100, is the initial zero. We buy 1 255 800 coul. Now we have to evaporate the water. How much heat do you need? The state of the unit is changing. That is, we will do it in mL, the mass is 3 kilograms. Specific heat capacity of evaporation It is 2,260,000, ie the water evaporates 6 780 000 coul to convert need energy and we must look at one step.

Steam at 100 degrees Turn to steam at 160 degrees. We must also do a mc delta T calculation, The mass of steam is 3 kilograms. The specific heat capacity of steam is 2010. The final temperature is 160. The initial temperature was 100, which also gives us 361,800 coul. It needs so much heat that minus 40 degrees ice cube Let's turn to steam at 160 degrees..

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Thermal Expansion of Water: Demonstration and Explanation

Lots of things expand when they get
warmer, for example air will expand. Like the air
and hot air balloons or even bridges will expand. That's why
they have to have a little metal teeth so that the bridges don't crack when
they expand. And of course water expands when it gets warmer. This is important because there's a lot of water on the planet Earth. And as the earth
gets warmer that water's going to expand and that expansion is gonna lead to sea
level rise. And that has a lot a big implications.

So to
experimentally show that water expands when it's heated we have a 100 watt light bulb and that is
in a reflective casing and we have a 750 milliliter
clear plastic bottle we have some food
coloring in there so it's visible and then we have a straw, and the straw
poked down through the bottle cap and it's sealed with a
little bit of caulk. so that no water can leak out. It's also
important to note that there's no air in the bottle or in the straw, below
the waterline, and that's important because
if we have air we're not really testing the thermal
expansion of water, we're looking at water and air we're not going to be able separate which
is which. So we're gonna start of it time equals 0 and we look at the
level of water in the straw. So at time equals 0 we have 13.5 millimeters of water in the straw. At
fifteen minutes it jumps up to 31 millimeters almost
double at 30 minutes we go to 43 millimeters and as that heat continues to make the
water warmer we jump up half-hour to 60 minutes at 71
millimeters another half hour, we're at ninety minutes
136 millimeters and finally we get to the 121 minute
mark that two hours and the waters almost at the top in the
straw 135 millimeters so that point we have to stop the
experiment because the water's gonna overflown we can't continue to measure at that point.

If we turn the light off
and we wait a while as the water cools it'll contract and
return to the original position. Now you might wonder why is all this
important we've shown that water expands as it's heated but why does it matter?
One reason that it matters is that the average global temperatures
are rising and they're only rising a little bit but
that little bit has big consequences Because we have quite a bit of water in the
ocean and even if that water only explains a little bit there's so
much of it that it contributes to sea level rise in fact thermal expansion along with ice
melting from the poles is one of the main things
that drives sea level rise so there you have it that's the thermal
expansion of water and one the consequences of
thermal expansion of water this is Dr.B, and thanks for
watching.

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TFD-2 Thermal Fingerprint Developer

the foster and Freeman thermal fingerprint developer or TFD uses a new chemical free thermal technique for developing prints without damaging the document it incorporates an ultra-low thermal mass conveyor specially designed to maximize uniformity of development and minimize cross contamination this video demonstrates how the TFT can easily be used to develop fingerprints on documents after turning on the machine the conveyor moves out of its parked position and the machine goes into standby mode to start the warm-up process just press the standby button on the control panel after the short warmup period the machine is then ready for use the development process is optimized by setting an appropriate conveyor speed here we are using the right hand up and down buttons to reduce the default speed of 3,000 millimeters per minute to a speed of 1500 milliliters per minute place the sample on the conveyor and press the Go button the development process starts as the conveyor moves under the heaters printer should now be developed if necessary the process can be repeated for further development the temperature of the document surface is displayed as it travels under the heaters here we are developing a print on a note to close down the machine after use press the standby button the conveyor then moves back to the parked position you can cancel the shutdown process by pressing the eject button when the machine has cooled down and is ready to be switched off and packed away the display will show standby to examine a document for fingerprints we use a crime light and matching goggles here we are examining a document that has had fingerprints applied first one side then the other as the document has not yet been treated no prints can be found the prints on this document are now developed by running it through the thermal fingerprint developer the develop prints can now easily be seen in fluorescence by using the crime light prints on both sides of the document have been developed you

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Prevent Thermal Bridging in Zero Energy Home (ZEH) Construction

we have a beam for the porch here that penetrates our exterior wall and to prevent thermal bridging it doesn't come all the way to the inside of the house it stops back here another thing you can see here is we've talked around the beam to prevent any air leaks get into the law.

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PDE | Heat equation: intuition

My goal in this video is to give you an intuitive description of the Heat equation. Now it's not going to be a derivation or a rigorous discussion, just an intuitive description. So the Heat equation is: 'u_t = gamma*u_xx'. And this equation is often referred to as the 'diffusion equation' because it describes a phenomenon of diffusion, and heat is just one good example of something which diffuses. Now gamma is a constant, greater than zero and it's often referred to as the 'thermal diffusivity'. And it will come from material properties of the model that we're dealing with.

And it will control the rate at which heat will diffuse. Let's start with an experiment: let's say we have a metal rod ..and we heat it up. So we put some candles underneath it
and we wait a little while. So you get some hot spots above the candles,
and as you move away from the flame it will cool down a little bit. Now let's take away those candles and let's make a few assumptions about what we've got. First thing to do will be: assume that the rod is small enough that the temperature is constant on cross-sections. This means that if we take a little slice of the rod, everwhere on that slice the temperature will be constant. Now this allows us to talk about the temperature of the rod using only one spatial co-ordinate: and that is the left-to-right position on the rod.

The other thing we'll assume is that the rod is insulated and essentially you can think of wrapping some insulation around the outside of it, so you'll lose no heat from this surface, and you'll only see the heat move back and forth inside the rod. Let's use the variable 'u' to represent the temperature in the rod at a horizontal position, 'x' and at time 't'. Another way to visualize this heat distribution we've drawn is simply as a graph of temperature versus position.

So if you fix a point in time and look at the temperature profile (as we've ..artistically rendered here) you can see the hot spots are these humps where it gets cool and then hot (like this.) So this is at some fixed point in time. Now the question is: what happens to the temperature as time passes? Now let's try to question this question just using our intuition. So let's start at the top of one of these hot spots. So go I over here to the hottest spot. Now everywhere I look around me in the rod ..it's cooler So sitting at the top of this hotspot
I have no choice but to cool down. The temperature must go down. (the same thing goes over here) Meanwhile at this cool spot, in-between the two peaks, down here in this 'valley', everywhere I look around in the rod it's warmer. So the temperature at this spot has no choice but to go up.

(it must get warmer.) I can represent this with some arrows,
so I'll draw some arrows in here. At the top of this hot spot it's cooling down, (the same thing over here) and in the middle it's warming up. Now let's move a little ways away. Let's move over here just to the right of this peak. What's happening here? Well, if I look to the left, it's warmer, and if I look to the right, it's cooler. But it's sort of more cool to the right than it is warm to the left, and so it seems like it's going to have to cool down.

Meanwhile if I look a little bit to the left of this cool spot it's sort of more warm to the left than it is cool to the right, so it's going to have to warm up. And these two will meet in the middle somewhere. So I can kind of fill in the rest of this picture with some arrows using this same intuition. And it's going to be cooling down a little bit more slowly further away from the peak at some point it will be 'not-changing' (at this instant in time.) and then it will be warming up on the other side (etc.) What does this picture mean? You may notice that these arrows I've drawn here look very much like they represent the concavity
of this temperature profile. Now they might be exactly the concavity, but they certainly have the same 'sign' as the concavity, and the simplest assumption would be that they're a constant multiple of the concavity – they're proportional to it.

The conclusion is then that the change in temperature is proportional to the concavity of the temperature profile, and that is in an equation: 'u_t'.. (which is the change in temperature) .. = 'gamma*u_xx' (being the concavity of the temperature profile.) So there may remain a small question about the 'sign' of gamma, and it's not too hard to figure out what the sign of gamma is. ..all we have to do is look at when the curve is concave up (so u_xx > 0.) So say were in this bowl here: the curve is concave-up and the temperature must be growing, so 'u_t' must be > 0. (and that would tell us that gamma is > 0.) Similarly. I could look at when the 'bowl' is facing down (concave down) and 'u_xx' would then be < 0, and so 'u_t' would have to be also < 0 (the temperature would be going down.) Another thing to notice here
is that if gamma is very large (for instance) 'u_t' would then be much larger in proportion to 'u_xx', and so saying that [gamma] is the 'thermal diffusivity' is not such a bad name for it because ..if it's very large then the heat will diffuse very quickly ..and if it's very small it will diffuse more slowly.

Now just because I like to look at things
in as many ways as possible: let's take away this picture of the temperature profile (that we drew here) and let's think about this in another way. Let's consider a point 'x' in rod (a little slice here) and some nearby slices: '(x – h)'… '(x + h)'. Now you'd expect that the temperature at this slice (at 'x') would be going 'up' if the average temperature near 'x' was bigger than the temperature at 'x'. And you'd expect [temperature] to go down if the average temperature near 'x' is smaller than 'x'. And ..that is represented by this quantity here: the average temperature near 'x' is: '(1/2)*(u(x+h,t) + u(x-h,t)'. So if the average temperature near 'x' is larger than [at] 'x', then this quantity will be positive. And if the average temperature near 'x' is smaller than the temperature at 'x' then this quantity will be negative. So the temperature at 'x' goes up or down
according to the sign of this quantity. Now you'll notice this looks a little bit like a difference-quotient in fact if I dress it up just a little bit (multiply by '2' divide by 'h^2') this becomes the difference quotient for the 2nd derivative 'u _xx'.

So I encourage you to work that out on your own (.. if it doesn't look familiar) So if I took the limit (as 'h' goes to 0) that would give me the second derivative with respect to 'x'. The sign of 'u_xx' is the same as the sign of this quantity So that says that 'u_xx' will be indicative of the temperature change at 'x'.

(according to this argument that we've presented.) So again, this is not a 'proof' of the Heat equation, but merely an intuitive description (a 'plausibility argument') that the Heat equation would be very simple way to describe the way in which heat diffuses inside a one-dimensional (more or less one dimensional) object like a thin rod. Now we'll find we can do a derivation of the Heat equation, and that will follow from a fundamental, physical principle known as the 'conservation of energy' (and we will do that shortly.).

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Ten Basic Plumbing Tools You Should Have At Home

Before entering the basics that one must have at home to survive a broken pipe, from our experts, we bring you some preliminary concepts to better understand the work of plumbers and then delve into a short review of how plumbing evolved until today and come up with a brief overview of some elementary tools.

What is plumbing?

It is an activity or a set of activities that are related to the installation and maintenance of pipes that allow the use of drinking water, as well as the evacuation of wastewater. It comes from the name of the material with which these pipes were formerly built, lead.

Plumbers, also called plumbers or in some countries of the continent, plumbing workers, in addition to installing a pipe, are trained to clean, repair, filter, whether in the bathroom, in the kitchen, or outside in the open air.

Soup

The best-known one has a wooden handle and a rubber suction cup—ideal for drains, bathtubs, and covered toilets.

Wrench

Also very common, it is a hand tool used to loosen or tighten nuts and bolts. It has an adjustable opening that allows you to adapt to different measures.

Teflon tape

It is a kind of adhesive tape, which is placed on the threads and union joints; it seals hermetically to avoid water leaks in pipes and stopcocks. Ensure that the joints between pipes, stopcocks, taps, sleeves, or other are fixed. Allow no leaks to leak.

Stillson Wrench or Grifa Wrench

It has the same function as the monkey wrench, and only its design allows to fit parts that the monkey wrench would not be able to do. It is an adjustable wrench used to tighten or loosen very resistant parts. It has teeth in the shape of a vise, making it capable of holding firmly without slipping.

Parrot Beak Clamp

It is a variant of the adjustable wrench, and it is an extendable plier, more robust, very useful due to the versatility of functions it can perform, allowing holding and adjusting elements of different thicknesses. They give rise to greater torque with less human force.

Mountain range

It consists of a blade with a serrated edge and is handled by hand or by other energy sources, such as steam, water, or electricity. Depending on the material to be cut, different types of saw blades are used.

Tube cutter

A tube cutter is a tool used to cut circular tubes at right angles. After making the cut, you may find some irregularities on the edges of the cut tube. Don’t worry, and you can remove them with a small file or an irregularity removal tool made for this purpose.

Drill

It is the most common tool when it comes to making a hole on a hard surface.

Chain key

It is a type of wrench with a special design that has a shank and a steel pivot where the chain is hooked. Furthermore, they are widely used in pipe installations where there is no wrench for the pipe diameter to be adjusted.

Snap Forceps

They are clamps that can be immobilized with their mouth in a certain position and thus cut, twist, or tear off various objects or materials.