In what units is specific heat capacity expressed? What is the laboratory work involved in measuring specific heat capacity? Some examples and meanings for various substances

05.04.2019, 01:42

Specific heat

Heat capacity is the amount of heat absorbed by a body when heated by 1 degree.

The heat capacity of a body is indicated by a capital Latin letter WITH.

What does the heat capacity of a body depend on? First of all, from its mass. It is clear that heating, for example, 1 kilogram of water will require more heat than heating 200 grams.

What about the type of substance? Let's do an experiment. Let's take two identical vessels and, having poured water weighing 400 g into one of them, and vegetable oil weighing 400 g into the other, we will begin to heat them using identical burners. By observing the thermometer readings, we will see that the oil heats up faster. To heat water and oil to the same temperature, the water must be heated longer. But the longer we heat the water, the more heat it receives from the burner.

Thus, different amounts of heat are required to heat the same mass of different substances to the same temperature. The amount of heat required to heat a body and, therefore, its heat capacity depend on the type of substance of which the body is composed.

So, for example, to increase the temperature of water weighing 1 kg by 1 °C, an amount of heat equal to 4200 J is required, and to heat the same mass of sunflower oil by 1 °C, an amount of heat equal to 1700 J is required.

A physical quantity showing how much heat is required to heat 1 kg of a substance by 1 °C is called the specific heat capacity of this substance.

Each substance has its own specific heat capacity, which is denoted by the Latin letter c and measured in joules per kilogram degree (J/(kg K)).

The specific heat capacity of the same substance in different states of aggregation (solid, liquid and gaseous) is different. For example, the specific heat capacity of water is 4200 J/(kg K) , and the specific heat capacity of ice J/(kg K) ; aluminum in the solid state has a specific heat capacity of 920 J/(kg K), and in liquid - J/(kg K).

Note that water has a very high specific heat capacity. Therefore, water in the seas and oceans, heating up in summer, absorbs a large amount of heat from the air. Thanks to this, in those places that are located near large bodies of water, summer is not as hot as in places far from the water.

Specific heat capacity of solids

The table shows the average values ​​of the specific heat capacity of substances in the temperature range from 0 to 10°C (unless another temperature is indicated)

Substance	Specific heat capacity, kJ/(kg K)
Solid nitrogen (at t=-250°C)	0,46
Concrete (at t=20 °C)	0,88
Paper (at t=20 °C)	1,50
Air is solid (at t=-193 °C)	2,0
Graphite	0,75
Oak tree	2,40
Tree pine, spruce	2,70
Rock salt	0,92
Stone	0,84
Brick (at t=0 °C)	0,88

Specific heat capacity of liquids

Substance	Temperature, °C
Gasoline (B-70)	20	2,05
Water	1-100	4,19
Glycerol	0-100	2,43
Kerosene	0-100	2,09
Machine oil	0-100	1,67
Sunflower oil	20	1,76
Honey	20	2,43
Milk	20	3,94
Oil	0-100	1,67-2,09
Mercury	0-300	0,138
Alcohol	20	2,47
Ether	18	3,34

Specific heat capacity of metals and alloys

Substance	Temperature, °C	Specific heat capacity, kJ/(kg K)
Aluminum	0-200	0,92
Tungsten	0-1600	0,15
Iron	0-100	0,46
Iron	0-500	0,54
Gold	0-500	0,13
Iridium	0-1000	0,15
Magnesium	0-500	1,10
Copper	0-500	0,40
Nickel	0-300	0,50
Tin	0-200	0,23
Platinum	0-500	0,14
Lead	0-300	0,14
Silver	0-500	0,25
Steel	50-300	0,50
Zinc	0-300	0,40
Cast iron	0-200	0,54

Specific heat capacity of molten metals and liquefied alloys

Substance	Temperature, °C	Specific heat capacity, kJ/(kg K)
Nitrogen	-200,4	2,01
Aluminum	660-1000	1,09
Hydrogen	-257,4	7,41
Air	-193,0	1,97
Helium	-269,0	4,19
Gold	1065-1300	0,14
Oxygen	-200,3	1,63
Sodium	100	1,34
Tin	250	0,25
Lead	327	0,16
Silver	960-1300	0,29

Specific heat capacity of gases and vapors

at normal atmospheric pressure

Substance	Temperature, °C	Specific heat capacity, kJ/(kg K)
Nitrogen	0-200	1,0
Hydrogen	0-200	14,2
water vapor	100-500	2,0
Air	0-400	1,0
Helium	0-600	5,2
Oxygen	20-440	0,92
Carbon(II) monoxide	26-200	1,0
Carbon monoxide	0-600	1,0
Alcohol vapor	40-100	1,2
Chlorine	13-200	0,50

/(kg K), etc.

Specific heat capacity is usually denoted by the letters c or WITH, often with indexes.

The specific heat capacity is affected by the temperature of the substance and other thermodynamic parameters. For example, measuring the specific heat capacity of water will give different results at 20 °C and 60 °C. In addition, specific heat capacity depends on how the thermodynamic parameters of the substance (pressure, volume, etc.) are allowed to change; for example, specific heat capacity at constant pressure ( C P) and at constant volume ( C V), generally speaking, are different.

Formula for calculating specific heat capacity:

$c=\backslash frac(Q)(\; m\backslash Delta\; T),$ Where c- specific heat capacity, Q- the amount of heat received by a substance when heated (or released when cooled), m- mass of the heated (cooled) substance, Δ T- the difference between the final and initial temperatures of the substance.

Specific heat capacity can depend (and in principle, strictly speaking, always, more or less strongly, depends) on temperature, therefore the following formula with small (formally infinitesimal) values ​​is more correct: $\backslash delta\; T$ And $\backslash delta\; Q$:

$c(T)\; =\; \backslash frac\; 1\; (m)\; \backslash left(\backslash frac(\backslash delta\; Q)(\backslash delta\; T)\backslash right).$

Specific heat values ​​for some substances

(For gases, the specific heat capacity in an isobaric process (C p) is given)

Table I: Standard Specific Heat Capacity Values

Substance	Physical state	Specific heat capacity, kJ/(kg K)
air (dry)	gas	1,005
air (100% humidity)	gas	1,0301
aluminum	solid	0,903
beryllium	solid	1,8245
brass	solid	0,37
tin	solid	0,218
copper	solid	0,385
molybdenum	solid	0,250
steel	solid	0,462
diamond	solid	0,502
ethanol	liquid	2,460
gold	solid	0,129
graphite	solid	0,720
helium	gas	5,190
hydrogen	gas	14,300
iron	solid	0,444
lead	solid	0,130
cast iron	solid	0,540
tungsten	solid	0,134
lithium	solid	3,582
	liquid	0,139
nitrogen	gas	1,042
petroleum oils	liquid	1,67 - 2,01
oxygen	gas	0,920
quartz glass	solid	0,703
water 373 K (100 °C)	gas	2,020
water	liquid	4,187
ice	solid	2,060
beer wort	liquid	3,927
Values ​​are based on standard conditions unless otherwise noted.

Table II: Specific Heat Capacity Values ​​for Some Building Materials

Substance	Specific heat capacity kJ/(kg K)
asphalt	0,92
solid brick	0,84
sand-lime brick	1,00
concrete	0,88
crown glass (glass)	0,67
flint (glass)	0,503
window glass	0,84
granite	0,790
soapstone	0,98
gypsum	1,09
marble, mica	0,880
sand	0,835
steel	0,47
soil	0,80
wood	1,7

See also

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Notes

Literature

• Tables of physical quantities. Handbook, ed. I. K. Kikoina, M., 1976.
• Sivukhin D.V. General course in physics. - T. II. Thermodynamics and molecular physics.
• E. M. Lifshits // under. ed. A. M. Prokhorova Physical Encyclopedia. - M.: “Soviet Encyclopedia”, 1998. - T. 2.<

Excerpt characterizing Specific Heat Capacity

- Does it work? – Natasha repeated.
– I’ll tell you about myself. I had one cousin...
- I know - Kirilla Matveich, but he’s an old man?
– It wasn’t always an old man. But here’s what, Natasha, I’ll talk to Borya. He doesn't need to travel so often...
- Why shouldn’t he, if he wants to?
- Because I know that this will not end in anything.
- Why do you know? No, mom, you don't tell him. What nonsense! - Natasha said in the tone of a person from whom they want to take away his property.
“Well, I won’t get married, so let him go, if he’s having fun and I’m having fun.” – Natasha smiled and looked at her mother.
“Not married, just like that,” she repeated.
- How is this, my friend?
- Yes, yes. Well, it’s very necessary that I don’t get married, but... so.
“Yes, yes,” the countess repeated and, shaking her whole body, laughed with a kind, unexpected old woman’s laugh.
“Stop laughing, stop,” Natasha shouted, “you’re shaking the whole bed.” You look terribly like me, the same laugher... Wait... - She grabbed both hands of the countess, kissed the little finger bone on one - June, and continued to kiss July, August on the other hand. - Mom, is he very much in love? How about your eyes? Were you so in love? And very sweet, very, very sweet! But it’s not quite to my taste - it’s narrow, like a table clock... Don’t you understand?... Narrow, you know, gray, light...
- Why are you lying! - said the countess.
Natasha continued:
– Don’t you understand? Nikolenka would understand... The earless one is blue, dark blue with red, and he is quadrangular.
“You flirt with him too,” said the countess, laughing.
- No, he is a Freemason, I found out. It’s nice, dark blue and red, how can I explain it to you...
“Countess,” the count’s voice was heard from behind the door. -Are you awake? – Natasha jumped up barefoot, grabbed her shoes and ran into her room.
She couldn't sleep for a long time. She kept thinking that no one could understand everything that she understood and that was in her.
"Sonya?" she thought, looking at the sleeping, curled up cat with her huge braid. “No, where should she go!” She is virtuous. She fell in love with Nikolenka and doesn’t want to know anything else. Mom doesn’t understand either. It’s amazing how smart I am and how... she’s sweet,” she continued, speaking to herself in the third person and imagining that some very smart, smartest and nicest man was talking about her... “Everything, everything is in her.” , - continued this man, - she is unusually smart, sweet and then good, unusually good, dexterous, swims, rides excellently, and has a voice! One might say, an amazing voice!” She sang her favorite musical phrase from the Cherubini Opera, threw herself on the bed, laughed with the joyful thought that she was about to fall asleep, shouted to Dunyasha to put out the candle, and before Dunyasha had time to leave the room, she had already passed into another, even happier world of dreams , where everything was as easy and wonderful as in reality, but it was only even better, because it was different.

The next day, the countess, inviting Boris to her place, talked with him, and from that day he stopped visiting the Rostovs.

On December 31, on New Year's Eve 1810, le reveillon [night supper], there was a ball at Catherine's nobleman's house. The diplomatic corps and the sovereign were supposed to be at the ball.
On the Promenade des Anglais, the famous house of a nobleman glowed with countless lights. At the illuminated entrance with a red cloth stood the police, and not only gendarmes, but the police chief at the entrance and dozens of police officers. The carriages drove off, and new ones drove up with red footmen and footmen with feathered hats. Men in uniforms, stars and ribbons came out of the carriages; ladies in satin and ermine carefully stepped down the noisily laid down steps, and hurriedly and silently walked along the cloth of the entrance.
Almost every time a new carriage arrived, there was a murmur in the crowd and hats were taken off.
“Sovereign?... No, minister... prince... envoy... Don’t you see the feathers?...” said from the crowd. One of the crowd, better dressed than the others, seemed to know everyone, and called by name the most noble nobles of that time.
Already one third of the guests had arrived at this ball, and the Rostovs, who were supposed to be at this ball, were still hastily preparing to dress.
There was a lot of talk and preparation for this ball in the Rostov family, a lot of fears that the invitation would not be received, the dress would not be ready, and everything would not work out as needed.
Along with the Rostovs, Marya Ignatievna Peronskaya, a friend and relative of the countess, a thin and yellow maid of honor of the old court, leading the provincial Rostovs in the highest St. Petersburg society, went to the ball.
At 10 o'clock in the evening the Rostovs were supposed to pick up the maid of honor at the Tauride Garden; and yet it was already five minutes to ten, and the young ladies were not yet dressed.
Natasha was going to the first big ball in her life. That day she got up at 8 o'clock in the morning and was in feverish anxiety and activity all day. All her strength, from the very morning, was aimed at ensuring that they all: she, mother, Sonya were dressed in the best possible way. Sonya and the Countess trusted her completely. The countess was supposed to be wearing a masaka velvet dress, the two of them were wearing white smoky dresses on pink, silk covers with roses in the bodice. The hair had to be combed a la grecque [in Greek].
Everything essential had already been done: the legs, arms, neck, ears were already especially carefully, like a ballroom, washed, perfumed and powdered; they were already wearing silk, fishnet stockings and white satin shoes with bows; the hairstyles were almost finished. Sonya finished dressing, and so did the Countess; but Natasha, who was working for everyone, fell behind. She was still sitting in front of the mirror with a peignoir draped over her thin shoulders. Sonya, already dressed, stood in the middle of the room and, pressing painfully with her small finger, pinned the last ribbon that squealed under the pin.

(or heat transfer).

Specific heat capacity of a substance.

Heat capacity- this is the amount of heat absorbed by a body when heated by 1 degree.

The heat capacity of a body is indicated by a capital Latin letter WITH.

What does the heat capacity of a body depend on? First of all, from its mass. It is clear that heating, for example, 1 kilogram of water will require more heat than heating 200 grams.

What about the type of substance? Let's do an experiment. Let's take two identical vessels and, having poured water weighing 400 g into one of them, and vegetable oil weighing 400 g into the other, we will begin to heat them using identical burners. By observing the thermometer readings, we will see that the oil heats up quickly. To heat water and oil to the same temperature, the water must be heated longer. But the longer we heat the water, the more heat it receives from the burner.

Thus, heating the same mass of different substances to the same temperature requires different amounts of heat. The amount of heat required to heat a body and, therefore, its heat capacity depend on the type of substance of which the body is composed.

So, for example, to increase the temperature of water weighing 1 kg by 1°C, an amount of heat equal to 4200 J is required, and to heat the same mass of sunflower oil by 1°C, an amount of heat equal to 1700 J is required.

A physical quantity showing how much heat is required to heat 1 kg of a substance by 1 ºС is called specific heat capacity of this substance.

Each substance has its own specific heat capacity, which is denoted by the Latin letter c and measured in joules per kilogram degree (J/(kg °C)).

The specific heat capacity of the same substance in different states of aggregation (solid, liquid and gaseous) is different. For example, the specific heat capacity of water is 4200 J/(kg °C), and the specific heat capacity of ice is 2100 J/(kg °C); aluminum in the solid state has a specific heat capacity of 920 J/(kg - °C), and in the liquid state - 1080 J/(kg - °C).

Note that water has a very high specific heat capacity. Therefore, water in the seas and oceans, when heated in summer, absorbs a large amount of heat from the air. Thanks to this, in those places that are located near large bodies of water, summer is not as hot as in places far from the water.

Calculation of the amount of heat required to heat a body or released by it during cooling.

From the above it is clear that the amount of heat required to heat a body depends on the type of substance of which the body consists (i.e., its specific heat capacity) and on the mass of the body. It is also clear that the amount of heat depends on how many degrees we are going to increase the body temperature.

So, to determine the amount of heat required to heat a body or released by it during cooling, you need to multiply the specific heat capacity of the body by its mass and by the difference between its final and initial temperatures:

Q = cm (t 2 - t 1 ) ,

Where Q- amount of heat, c— specific heat capacity, m- body weight, t 1 — initial temperature, t 2 — final temperature.

When the body heats up t 2 > t 1 and therefore Q > 0 . When the body cools down t 2i< t 1 and therefore Q< 0 .

If the heat capacity of the entire body is known WITH, Q determined by the formula:

Q = C (t 2 - t 1 ) .

In today's lesson we will introduce such a physical concept as the specific heat capacity of a substance. We learn that it depends on the chemical properties of the substance, and its value, which can be found in the tables, is different for different substances. Then we will find out the units of measurement and the formula for finding specific heat capacity, and also learn to analyze the thermal properties of substances based on the value of their specific heat capacity.

Calorimeter(from lat. calor– warmth and metor- measure) - a device for measuring the amount of heat released or absorbed in any physical, chemical or biological process. The term “calorimeter” was proposed by A. Lavoisier and P. Laplace.

The calorimeter consists of a lid, an inner and an outer glass. It is very important in the design of the calorimeter that there is a layer of air between the smaller and larger vessels, which, due to low thermal conductivity, ensures poor heat transfer between the contents and the external environment. This design allows you to consider the calorimeter as a kind of thermos and practically get rid of the influence of the external environment on the heat exchange processes inside the calorimeter.

The calorimeter is intended for more accurate measurements of specific heat capacities and other thermal parameters of bodies than indicated in the table.

Comment. It is important to note that such a concept as the amount of heat, which we very often use, should not be confused with the internal energy of the body. The amount of heat is determined precisely by the change in internal energy, and not by its specific value.

Note that the specific heat capacity of different substances is different, which can be seen in the table (Fig. 3). For example, gold has a specific heat capacity. As we indicated earlier, the physical meaning of this value of specific heat capacity means that in order to heat 1 kg of gold by 1 °C, it needs to be supplied with 130 J of heat (Fig. 5).

Rice. 5. Specific heat capacity of gold

In the next lesson we will discuss calculating the value of the amount of heat.

Listliterature

1. Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. / Ed. Orlova V.A., Roizena I.I. Physics 8. - M.: Mnemosyne.
2. Peryshkin A.V. Physics 8. - M.: Bustard, 2010.
3. Fadeeva A.A., Zasov A.V., Kiselev D.F. Physics 8. - M.: Enlightenment.

1. Internet portal “vactekh-holod.ru” ()

Homework

The amount of energy that must be supplied to 1 g of a substance to increase its temperature by 1°C. By definition, in order to increase the temperature of 1 g of water by 1°C, 4.18 J is required. Ecological encyclopedic dictionary.... ... Ecological dictionary

specific heat- - [A.S. Goldberg. English-Russian energy dictionary. 2006] Energy topics in general EN specific heatSH ...

SPECIFIC HEAT- physical a quantity measured by the amount of heat required to heat 1 kg of a substance by 1 K (cm). SI unit of specific heat capacity (cm) per kilogram kelvin (J kg∙K)) ... Big Polytechnic Encyclopedia

specific heat- savitoji šiluminė talpa statusas T sritis fizika atitikmenys: engl. heat capacity per unit mass; mass heat capacity; specific heat capacity vok. Eigenwärme, f; spezifische Wärme, f; spezifische Wärmekapazität, f rus. mass heat capacity, f;… … Fizikos terminų žodynas

See Heat capacity... Great Soviet Encyclopedia

specific heat- specific heat... Dictionary of chemical synonyms I

specific heat capacity of gas- - Topics oil and gas industry EN gas specific heat ... Technical Translator's Guide

specific heat capacity of oil- - Topics oil and gas industry EN oil specific heat ... Technical Translator's Guide

specific heat capacity at constant pressure- - [A.S. Goldberg. English-Russian energy dictionary. 2006] Topics: energy in general EN specific heat at constant pressurecpconstant pressure specific heat ... Technical Translator's Guide

specific heat capacity at constant volume- - [A.S. Goldberg. English-Russian energy dictionary. 2006] Topics energy in general EN specific heat at constant volumeconstant volume specific heatCv ... Technical Translator's Guide

Books

• Physical and geological foundations of the study of water movement in deep horizons, V.V. Trushkin. In general, the book is devoted to the law of self-regulation of the temperature of water with a host body, discovered by the author in 1991. At the beginning of the book, a review of the state of knowledge of the problem of movement of deep...