Heat has varying effects on various compounds. On a hot day, a metal chair placed in direct sunlight may get very warm to the touch. In the same sun, a same body of water won’t get nearly as warm. To raise an object’s temperature by one degree Celsius, we would state that water has a large heat capacity. In contrast to metals generally, water has a high degree of thermal resistance. The energy needed to raise the temperature of one gram of a substance by one degree Celsius is known as a substance’s specific heat.
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What is Heat?
Heat is a form of energy transferred from hotter to colder substances.
We will feel heated if we touch, for instance, a hot mug of coffee because the mug transmits its energy (heat) into our body. In contrast, when we touch a glass of cold water, heat energy from our bodies transfers to the glass.
Take the boiling of water into account to comprehend heat as a transferable energy source. When a vessel filled with water is set on a burning stove, the bottom of the vessel first warms up, then the water continues to warm up until it ultimately begins to boil. While a body’s temperature is a measure of its hotness or coolness and influences the direction of heat flow, the order in which heat is transferred is directly tied to the temperature of the vessel and the water.
Thus, the two systems must have different temperatures for heat energy to transfer from one to the other. Then, until the two systems attain the same temperature, heat will go from the hotter system to the colder system. Take a mental picture of a bucket half-filled with scalding hot water. Cold water is poured to the bucket to make the water a little bit colder. When the combination reaches an intermediate temperature, the hot water’s heat has finished warming up the cold water. A key distinction is that ‘hotness’ is what moves across systems, whereas ‘coldness’ is only the absence of heat.
What is Heat Capacity?
The quantity of heat needed to raise an object’s temperature by one degree is known as its heat capacity. In addition, it is also the ratio between the quantity of energy transferred to an object and the resulting temperature rise.
Moreover, the heat capacity measurement is expressed in Joules per degree Celsius. Therefore the object’s mass affects it. To enable comparison between objects of comparable mass, it is frequently stated in terms of 100 grams.
Energy per degree is measured in Heat Capacity.
The amount of heat used to heat an object can be written as:
Q = C dt
where
Q = amount of heat supplied (J)
C = heat capacity of system or object (J/K)
dt = change in temperature (K, C, or oF)
Formula for Heat Capacity
Heat capacity (C), also known as thermal mass, is the quantity of energy in Joules needed to raise the temperature of a particular item by one degree Celsius.
Heat capacity is a broad attribute that depends on the size or amount of a specific substance. Joules per Kelvin or joules per degree Celsius are the units used to measure heat capacity.
Mathematically,
Q = C ΔT
Where;
Q is the amount of heat energy needed to alter the system’s temperature by ΔT, and C is the system’s heat capacity.
Specific Heat Capacity
A substance’s specific heat capacity is the amount of energy needed to raise one kilogram of that material by one degree Celsius.
4,200 Joules per kilogram per degree Celsius (J/kg°C) is the specific heat capacity of water. So, 4,200 J are required to raise the temperature of 1 kilogram of water by 1°C.
For thermodynamic investigations, scientists required a number that is independent of the amount or size of materials, therefore they defined specific heat capacity. It’s an intense property since it doesn’t change based on how much or how little matter there is. An object’s specific heat capacity is the amount of heat energy needed to increase its temperature by one Kelvin per kilogram of mass. It may be expressed mathematically as:
Q= m c ΔT
Thus, Q is the heat energy needed to raise or lower the temperature of m (kg) of a substance by T, and s is its specific heat capacity.
Thermodynamics continues to play an important part in our lives, either directly or indirectly. The rules of thermodynamics are used by scientists and engineers to develop more effective and productive methods for carrying out chemical reactions. The principles of thermodynamics are used by chemical and mechanical engineers to develop more effective and efficient heat engines.
| Material | Specific Heat Capacity (J/gºC) |
|---|---|
| Al | 0.902 |
| C (graphite) | 0.720 |
| Fe | 0.451 |
| Cu | 0.385 |
| Au | 0.128 |
| NH3 (ammonia) | 4.70 |
| H2O (l) | 4.184 |
| C2H5OH (l) (ethanol) | 2.46 |
| (CH2OH)2 (l) (ethylene glycol, antifreeze) | 2.42 |
| H2O (ice) | 2.06 |
| CCl4 (carbon tetrachloride) | 0.861 |
| CCl2F2 (l) (a chlorofluorocarbon, CFC) | 0.598 |
| Wood | 1.76 |
| Concrete | 0.88 |
| Glass | 0.84 |
| Granite | 0.79 |
Molar Specific Heat
The molar specific heat of a solid or liquid of a substance is the amount of heat required to increase the temperature of one mole of solid or liquid by 1K or 1° C. It is measured in units of joules per molecule per kelvin.
Specific Heat at Constant Pressure or Volume
When heated across a narrow temperature range, the volume of a solid does not change. This is known as the specific heat at a constant volume. It is abbreviated as CV.
When heated within a narrow temperature range, the pressure of a solid does not change. This is known as the specific heat at constant pressure, which can be written as CP.
The pressure and volume change in temperature, as well as the amount of heat necessary to raise the temperature of 1 gram of gas by 1°C, all vary depending on the method used to heat the gas. You may heat the gas with various P and V values.
Therefore, specific heat has an infinite range of values. If the heat source is varied, the gas’s specific heat will change. Hence, specific heat must be maintained at a fixed pressure or volume. For a perfect gas,
CP – CV = nR
where;
CP is heat capacity at constant pressure
CV is heat capacity at constant volume
n is amount of substance, and
R=8.314 J mol−1 K and is the molar gas constant.
Applications of Specific Heat
- Cooking utensils are made from a low-specific-heat material. Rapidly heating their undersides is possible. This is because their bases are made of polished aluminum or copper. In order to protect our hands from the intense heat, the handles of these tools are manufactured with a high specific heat material.
- Materials with a high specific heat are used as insulators. Use wood as an example. In either a very hot or very cold climate, a wooden home would be an excellent choice.
- Swimming pools used to have cooler water than the surrounding air because water has a high specific heat.
You might have noticed that if you are trying to boil a lot of water it takes longer than if you only wish to boil a small amount of water. This is all because of something called ‘heat capacity’. Keep watching to learn more.
References
- Halliday, David; Resnick, Robert (2013). Fundamentals of Physics. Wile
- Yunus A. Cengel and Michael A. Boles,Thermodynamics: An Engineering Approach, 7th Edition, McGraw-Hill,
- https://byjus.com/chemistry/heat-capacity-and-specific-heat-capacity/
- https://www.toppr.com/guides/physics-formulas/heat-capacity-formula/
- https://www.toppr.com/guides/physics/thermal-properties-of-matter/specific-heat-capacity/
- https://www2.chem.wisc.edu/deptfiles/genchem/netorial/modules/thermodynamics/enthalpy/enthalpy3.html
- Emmerich Wilhelm & Trevor M. Letcher, Eds., 2010, Heat Capacities: Liquids, Solutions and Vapours, Cambridge, U.K.:Royal Society of Chemistry
- engel, Yunus A. and Boles, Michael A. (2010) Thermodynamics: An Engineering Approach, 7th Edition, McGraw-Hill
