Specific heat (cp) or specific heat capacity refers to the amount of heat required to raise the temperature of one kilogram mass of a substance by one Kelvin temperature.
Its formula is Q/m ΔT = cp, where Q refers to the amount of heat supplied to the specimen and ΔT is the rise in temperature.
The value of cp depends on the nature of the substance.
Table of Contents
Simple Words Explanation
Specific heat is the amount of heat that must be added (or removed) from a unit mass of a substance to change its temperature by one degree Celsius. It is an intensive property. In simple words, equal masses of different substances needed different amounts of heat to raise them through the same temperature interval.
Specific Heat Formula
Consider the temperature of a body of mass “m” changes by ΔT. The amount of heat (Q) absorbed or released by a body is proportional to its mass and change in temperature.
Q ∝ mass of the body (m) ………(1)
Q ∝ change in temperature (ΔT) ………(2)
Combining equation 1 and equation 2
Q ∝ mΔT ⇒ Q = cp.m.ΔT
Where cp is the constant of proportionality, it depends on the nature of the substance.
The formula shows that the transfer of heat to an object depends upon two factors:
- The change in temperature
- The mass of the system
As per the formula, to cause an equivalent temperature change in a doubled mass, you need to add twice the heat. A substance’s heating capacity depends on temperature and pressure, so cp is typically determined at a constant temperature and pressure, typically 25 degrees Celsius.
| Specific heat definition | The amount of heat required to increase the temperature of the one-kilogram mass of a substance by one Kelvin temperature is referred to as specific heat (cp). |
| Specific heat of air constant pressure | 1.005 kJ kg-1 K-1 |
| Specific heat of air constant volume | 0.718 kJ kg-1 K-1 |
| Specific heat of water | 4.179 kJ kg-1 K-1 |
Key Points
- It is the capacity of a substance that depends on the nature of the material.
- S.I unit is J/(kg⋅K) or J/(kg⋅C).
- It is an intensive property that depends only on the type and phase of a substance.
- cp is independent of mass or volume.
- As per the mathematical formula, constant (cp) = ΔQ if the temperature change of 1 kg mass is 1K.
- It is another physical property of matter.
- The cp of a gallon of milk is equal to the cp of a quart of milk.
- It does not depend upon the size of the object, unlike heat capacity.
- Water has an extremely high cp capacity, which makes it good for temperature regulation.
- The cp of copper (Cu) is 0.385 J/g °C. This means that 1 gram of Cu takes 0.385 joules of heat to raise its temperature by 1 degree Celsius.
Specific Heat of Water
The specific heat of water is 4182 J/kg°C, which is higher than any other common substance. As a result, water plays a very important role in temperature regulation.
The cp of water is five times that of glass, which means that it takes five times as much heat to raise the temperature of water the same amount as for glass.
Specific Heat Formula- Sample Problem
A container has 2.5 liters of water at 20°C. What is the cp required to boil the water? The density of water is 1000 kgm-3 and the cp of water is 42000 J Kg-1 k-1
The volume of water is 2.5 liters and the mass of water is 2.5 kg.
Initial temperature T1 = 20 °C
Final temperature T2 = 100 °C
ΔT = T2-T1
= 100°C-20°C = 80°C or 80K
Q= cp.m.ΔT = 42000 x 2.5 x 80 = 840000J = 840 kJ
Summary
- Specific heat refers to the exact amount of heat needed to make one unit of mass of a substance one degree warmer.
- The specific heat formula is Q = m.ΔT.cp
- The SI unit of cp is joule per kilogram per kelvin
- The cp of water is 4182 J/kg°C
Related Topics
Room Temperature| Comfortable Temperature
What is Auxiliary Heat?
The Density of Water lbs/U.S gal
The pH of Distilled/ De-Ionized Water
Frequently Asked Question
Some of the frequently asked questions are given below
1. What is heat flux?
The quantity of heat transferred per unit area per unit time to or from a surface is referred to as heat flux.
2. What is a water molecule and how many hydrogen atoms are in a molecule of water?
Water is a substance that exists in gaseous, liquid, or solid phases and is made up of the chemical elements hydrogen and oxygen. It is one of the most abundant and necessary chemicals. At room temperature, it is a tasteless and odorless liquid with the critical capacity to dissolve many other compounds. Water’s capacity as a solvent is critical to living creatures.
A water molecule consists of two hydrogen atoms attached to the sides of a single oxygen atom.
3. What is thermite welding?
Thermite welding is a type of welding that involves reducing metal oxides with aluminum powder and releasing a large quantity of heat. A thermite reaction is used to repair railway rails or broken machine components.
4. What is the specific heat of air?
The specific heat of air at constant pressure is 1.005 kJ/kg K and the specific heat of air at constant volume is 0.718 kJ/kg K. The specific heat (C), also called heat capacity, of a substance is the amount of heat required to raise its temperature by one degree.
5. Combustion reaction?
Combustion is a chemical process that produces both heat and light. The most prevalent sort of combustion is fire. When the gas oxygen interacts with another material, the majority of combustion happens.
6. What is the sublimation process?
Sublimation is the process by which a solid turns straight into a gaseous state without first going through the liquid stage. Dry ice is one of several sublimation instances (frozen carbon dioxide).
7. The process of distillation?
Distillation is the separation of a mixture of liquids based on variations in their boiling points (or volatility). Water may be extracted from a salt solution using this method.
8. Gauge pressure?
Gauge pressure, often known as overpressure, is the pressure in a system that is greater than atmospheric pressure. Because gauge pressure is zero-referenced against ambient air (or atmospheric) pressure, gauge pressure values include atmospheric pressure.
Specific heat capacity is the heat required to raise the temperature of a substance by 1 degree Celsius. Heat capacity is the ratio of heat absorbed by a material to the temperature change.
The specific heat formula is the amount of heat supplied to the specimen, divided by the resulting temperature increase. cp is related to the unit mass of the specimen. The mathematical form of the formula is Q/m ΔT = cp where Q refers to the amount of heat supplied to the specimen and ΔT is the rise in temperature.
Related Topics
Is Water a Mixture?
Soft Water vs. Hard Water
The Specific Gravity of Water
Boiling of Water
What is Fresh Water?
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