Prashiddha Bista • 39 Reads
Heat is a very important source of energy. We use heat for different purposes in our daily life. Heat is the total kinetic energy of molecules that provides us with the sensation of warmth. Heat can flow from hotter to colder bodies. Heat as energyHeat energy is the result of the movement of tiny particles called atoms, mol...
Prashiddha Bista • 40 Reads
Temperature, a measure of hotness or coldness expressed in terms of several arbitrary scales and indicating the direction in which heat energy will spontaneously flow i.e. from hot body to cold body. Temperature is not the equivalent of the energy of a thermodynamic system; e.g., a burning match temperature is much higher tha...
Prashiddha Bista • 68 Reads
video for types of thermometerSpecific heat capacity is the amount of heat required to change the heat content of exactly 1 gram of a material by exactly 1°C.Here is a table for SHC of some materials:S.No.Materials'S' in Jkg-1°C-11.Lead1262.Gold1303.Mercury1404.Silver2345.Brass3806.Copper3807.Steel4478.Alcohol25909.Water42001...
The total sum of kinetic energy contained by the molecules of the body is called the heat energy of that body.
Its SI unit is Joule.
The amount of heat required to increase the temperature of 1 gm of pure water by 1ºc is called 1 calorie heat.
Here, 1 Calorie = 4.2 Joules.
Any effects of heat are:
The degree of hotness or coldness of a body is called temperature.
Its SI unit is Kelvin.
The difference between heat & temperature are:
|It is the form of energy.||Temperature is the degree of hotness or coldness of a body.|
|It is measured by a caloriemeter.||It is measured by a thermometer.|
|Its SI unit is Joule.||Its SI unit is Kelvin.|
|It is the cause of temperature.||It is the effects of heat.|
The freezing and boiling point of alcohon and mercury are:
Mercury ---> FP: - 39°C
Alcohol ---> FP: - 115°C
We can measure the temperature of 100°C with a mercury thermometer but not with an alcohol thermometer. Why?
We all know that the FP of alcohol is - 1150C and BP is780C. But the FP of mercury is - 350C and BP is 3570C. So, mercury has a normal physical state at 1000C and can measure temperature. But, alcohol starts boiling if the temperature raised to 780C. So, it changes to a gas state at 1000C and cannot measure temperature. Hence, we can measure the temperature of 1000C with a mercury thermometer but not with an alcohol thermometer.
The thermometer that is used in labs having the range from -100C to 1100C is called a laboratory thermometer.
It consists of a thick-walled capillary made up of glass in which one end is closed and its other end has a cylindrical bulb. This bulb and a small portion of the capillary is filled with pure mercury. The air from the tube is completely taken out before closing the upper end. The vacuum created brings easiness in the labeling of temperature.
Any 2 thermometer scales that are very popular are:
The main parts thermometer are:
The thermometer used in different clinics & hospitals for clinical purposes like measuring human temperature, etc. is called a clinical thermometer.
It has graduations from 35°C to 42°C or 95ºF to 107.6°F because the temperature of the human body varies only in this range.
The digital thermometer is the modern thermometer that shows the temperature in the form of digits. So, it doesn't have any calibration on it.
A digital thermometer has a built-in sensor. It determines the amount of heat and displays them on the monitor (display).
The thermometer that is used to measure the maximum and minimum atmospheric temperature of twenty-four hours of a particular place is called the maximum & minimum thermometer.
The specific heat capacity of any substance is defined as the amount of heat required to raise the temperature of 1 kg mass of that substance by 1°C.
Its SI unit is J/kg°C.
The specific heat capacity of water is 4200 J/Kg0C means 4200 joules of heat energy are required to raise the temperature of 1 kg water by 1ºC.
When any hot body is cooled, it gives out heat, and its temperature falls. Also, when any cool body is heated, it absorbs heat, and its temperature rises. It has been proved that heat gained or lost is directly proportional to:
Combining 1 and 2, we get:
Q ∝ mdt
or, Q = msdt where s is constant called specific heat capacity of the body.
Therefore, Q = msdt is the heat equation.
The relation between temperature and molecular vibrations of a body is:
temperature ∝ molecular vibrations of the body
It means if the body is vibrated more the temperature increases and vice versa.
Calorimetry is the measurement of heat lost or gained by an object.
The principle of calorimetry state that 'When a hot body is mixed with a cold body, the heat lost by the hot body is equal to the heat gained by the cold body, provided that no heat escapes to the surroundings.'
Therefore, Heat lost = Heat gained.
We know from the principle of calorimetry that the heat gained by a cool body from a hot body is equal to the heat lost by a hot body. To cool the engines, something should absorb its heat and water has the highest capacity to absorb heat as its specific heat capacity 4200 J/Kg0C.
So, water is used to cool the engines of machines.
As we all know that water has the highest specific heat capacity. It means that it has the highest capacity of absorbing heat. So, the heated water releases heat for the longest time. As the hot bottles are used for heating purposes, hot water is used in them.
We know that the density of solid ghee is more than that of liquid or hot ghee. So while freezing, all the frozen ghee starts to displace to the bottom. But, water has a higher density at 40C than at 00C. It means water has a higher density than ice. So, while freezing, ice displaces to the top.
When we go out of bed on a very cold morning, we feel cold but when we come back to the same room after strolling in the open air we feel warm. Why?
We all know that, the temperature of our body higher in the bedroom than the temp. of surrounding. So, when we go outside, our body loses the heat and we feel cold.
After strolling outside in open air the temp of our body again decreases below the temp. of bedroom. So, when we come back to the bedroom, our body gains heat and we feel warm.
We know that in the desert the land is covered all by sand. Sand has low specific heat capacity which means it gains and loses heat very fast. So, during the day it gains max heat and becomes hotter and during the night it loses all the heat and becomes very cold.
We know that mercury is only the metal that exists in the state of liquid with a freezing point - 39°C and boiling point 357°C. The range of its FP and BP is suitable for measuring normal temp. It is also a good conductor of heat. It has a low specific heat capacity i.e.140 J/Kg°C. So, it is used as a thermometric liquid.
We all know that water has the highest specific heat capacity. So, it absorbs more heat and also loses more heat. During the day, the heat near the sea area is absorbed by water in the sea and during the night the area near the sea absorbs heat from the sea.
So, the temp near the sea remains moderate.
In the winter season, the morning temp. on the earth's surface is very low. But the inner core of the earth is always hot. We know, well water is absorbed from deep inside the ground. At that surface, water absorbs the heat from the earth's core and remains hot. When the same water is brought to the surface, the temp. of water is higher than that of surroundings. So, well water is felt to be warmer in the morning during the winter.
A new quilt has high air storage capacity as it is thicker than the old one, But the old quilt can't store more air as it is compressed by several uses. So, a new quilt acts as a better insulator than the old one. So, a new quilt prevents our body's heat to be released into the atmosphere in a better way than the old one. Hence, a new quilt is warmer than an old one.
Study the given table and answer the following questions.
|Substances||Sp. heat capacity|
a. What is meant by the statement the specific heat capacity of B is 470 J/Kg0C?
b. If an equal amount of heat is given to an equal mass of these substances, which one will have the highest and which one will have the lowest temperature? Why?
c. If an equal mass of these substances at 1000C temperature are kept on a wax slab, which one will make the deepest hole on the wax slab? Why?
It means one kilogram mass of B requires 470J of heat to raise its temp. by 10C.
C will have the highest temperature because it has the lowest sp. heat capacity and B will have the lowest temperature because it has the highest sp. heat capacity.
From: sp. heat capacity ∝ 1/temperature.
B will make the deepest hole in the wax slab because it has more heat to release to the wax slab as it is with constant mass and temp. with the highest sp. heat capacity.
Water boils at 100°C . Ocean water changes into vapour to form cloud though ocean doesn't have 100°C temperature . Why ?
The formation of cloud above ocean is due to evaporation, not boiling. And evaporation takes place in any temperature. So ocean water need not to be 100 degree Celsius for forming cloud.