2 March 2024

specific heat It is a fundamental concept in thermodynamics that describes the amount of energy required to increase the temperature of a substance by one unit. This physical property is crucial to understanding how materials store and release thermal energy, and how they behave under different thermal conditions.

Although it may seem abstract, understand specific heat it is fundamental to understanding how many things work in the physical world around us. keep reading and learn what is specific heat and how it relates to the elements you use in daily life.

What is the specific heat calculation used for?

Calculation of specific heat used to determine the amount of energy It takes to raise or lower the temperature of a substance. It is also useful to know how heat transfer behaves in different materials and how this change will affect their use and handling.

This calculation is applied in many fields such as the oil and refining industry, engineering, physics and other scientific areas where understanding of the heat transfer and the thermal behavior of materials is important.

In each area, specific heat has many practical applications such as:

  • design systems refrigeration or heating.
  • Design and selection of materials in the construction of different objects.
  • Estimate the consumption of fuel or electric power.
  • elaboration and the conservation food.
  • measurement of thermal properties of the materials.
  • Study of phase changes or chemical reactions that involve heat.
  • At the CSIC for research environmental and medical.

Specific Heat Formulas

For calculate the amount of heat that it takes to change the temperature of a substance different formulas apply.

First, it is important to indicate how specific heat is expressed: it is expressed in units of joules per gram and degree Celsius (J/g°C) or kilocalories per kilogram and degree Celsius (kcal/kg°C).

most usual formula To calculate the specific heat of a substance:

c^=m.ΔtQ​

Explanation: Q represents the heat energy transfer between the system and its surroundings, m the mass of the system and Δt the temperature variation to which it is subjected.

another formula to express the specific heat is:

c=Δt→0lim​m.ΔTQ​=m1​dTdQ​

Explanation: Q is the heat absorbed, m the mass of the substance, T the temperature of the substance and dQ/dT the derivative of heat with respect to temperature.

Formula for the calculation of heat absorbed or released by a substance:

Q=mcΔT

Explanation: Q is the heat transferred, m the mass of the substance, c the specific heat of the substance and ΔT the temperature change.

Important:

The amount of heat (Q) is positive or negative depending on whether the substance absorbs or gives up thermal energy.

  • When Q is positive, it means that the substance has absorbed thermal energy and its temperature has increased.
  • When Q is negative, it means that the substance has released thermal energy and its temperature has decreased.

Table of specific heat of materials

Here is a table with some examples of materials and their respective specific heats in calories per gram and degrees Celsius (cal/g°C) that indicate how much energy it will take to raise the temperature of each material by one unit.

Substance / (cal/g°C)

Olive Oil: 0,400

Steel: 0.110

Water: 1,000

Alcohol: 0.600

Alpaca: 0.095

Aluminum: 0.217

Antimony: 0.050

Sulfur: 0.179

What is heat, temperature and energy?

Heat, temperature and energy are concepts that are used to describe the behavior of matter at the molecular level. These are closely related concepts, so the difference between them can be a bit confusing.

The main difference is that heat is related to thermal energy, while temperature is more related to molecular kinetic energy. Next, we briefly explain what each one means:

heat is thermal energy that is transferred from a warmer system to a cooler one, which are in contact. This energy is measured in units of joules (J) or calories (cal), and is represented by the symbol Q or q.

Heat measures the movement or flow of energy. Therefore, an object can gain or lose heat, but it cannot ‘have heat’, since it is a measure of change, never a property that an object or system possesses.

temperature is kinetic energy average of the molecules in a material or system and is measured in Celsius (°C), Kelvin (K), Fahrenheit (°F) or Rankine (R). It is a measurable physical property of an object, also called a ‘state variable’.

It is an intensive property, that is, it does not depend on the amount of matter in the system, but only on its thermal state.

Energy designates “the ability to perform transformations”. For example, it is what allows to give work, produce movement, modify the temperature or change the state of matter. Energy is measured in units of joules (J) or kilowatt-hours (kWh), and is represented by the symbol E or U.

At the same time, energy can exist in different forms, such as mechanical, chemical, electrical, radiant, or thermal.

What is the heat capacity of an element?

Here we refer to the amount of heat needed to raise the temperature of a certain amount of that element in one degree, either Celsius or Kelvin. A distinction is made between heat capacity at constant pressure and constant volume.

Example:

A system consisting of 200 g of liquid water at 25 °C will have a heat capacity of 836 JK- ¹.

Being an extensive property, depends on the amount of matter that the element has. For example: it takes more heat to raise the temperature of 10 g of iron than of 5 g of iron.

What is specific heat of a substance?

The specific heat of a substance is a physical quantity that indicates the ability of a material to store energy internal in the form of heat. It is defined as the amount of heat that must be supplied to the unit mass of a substance to raise its temperature by one unit.

This value is represented by the letter c (lowercase) and is measured in various units, such as joules per kilogram per kelvin (J/kg K) or calories per gram per degree Celsius (cal/g °C).

Example of measured substances (cal/g°C)

  • Olive oil: 0.40
  • Ethyl alcohol: 0.60
  • Potassium: 0.019

What is specific heat of water?

The specific heat of water is a physical property that is defined as the amount of heat that must be supplied to the unit mass of water to raise your temperature in a unit.

The value of the specific heat of water depends on the temperature and pressure to which the water is found, but in general it is very high compared to other substances.

Water has an exceptionally high specific heat of about 4 J/gK and exhibits anomalous behavior with a minimum specific heat of around 35°C.

The specific heat of water is 1 cal.g-1.° C-1.

This means that to raise the temperature of 1 g of water by 1°C requires 1 cal of energy, and to raise the temperature of ice by one degree to -5°C requires 0.5 calories, while to make the same with 1 g of copper only 0.092 cal is needed.

The specific heat of a metal is the amount of heat required to raise the temperature of one gram of metal in one degree Celsius.

To measure the specific heat of a metal, a calorimetry method called the mixture method can be used, which consists of putting the hot metal in contact with cold water and measure the final temperature of both. However, this varies depending on the type of metal and the initial temperature. However, this varies according to the type of metal and the initial temperature.

Examples of metals measured in (cal/g°C):

  • Iron: 0.107
  • Gold: 0.0308
  • Copper: 0.0924
  • Aluminum: 0.217
  • Mercury: 0.0033
  • Silicon: 0.168

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