[Physics Class Notes] on Relation Between Calorie and Joule Pdf for Exam

Joule is the S.I. unit of heat (which is a form of energy and also a derived unit of energy and is a measure of doing work or generating heat) generally represented by “J”. It is equal to the energy transferred to a body when 1 N force acts on it to displace it by 1 m in the direction of the force.

Calorie and Joule

1 Calorie is the amount of heat required at a pressure of 1 standard atmosphere to raise the temperature of 1gram (g) of water through 1 degree Celsius. 

Joule and Calorie both are units of heat or energy variously defined. The relation between Joule and Calorie can easily be depicted with a simple formula i.e. 

1 calorie (cal) = 4.184 (approx 4.2) Joule, which is wholly elaborated in this article 

How to Convert Joule into Calorie?  

For International use, caloric is defined as the amount of heat required to raise the temperature of 1 gram (g) of water from 14.5 degrees Celsius to 15.5 degrees Celsius. 

Joules (J) and calories (Cal) are the most widely used energy and heat units. For joule calorie conversion it becomes more daunting tasks for the conversion of 1 joule to Calorie because it involves the division of the coefficient with a hectic value of 0.2390057361. It is quite a bit easier to convert Calorie into Joule as it involves the multiplication of coefficient with 4.18.

Quick Conversion Chart of Joule into Calories

What is the Relation between Calorie and Joule? 

As we know, energy is the ability to do work. Heat is also a form of energy. Both heat and energy can be measured using multiple units, and calories and joules are also examples of such heat units. 

And as you know, the relation between Calorie and Joule is proportional to each other which means that any change in the Calorie (cal) will also lead to a change in its equivalent value in joules (J). It also implies that Joule (J) is directly proportional to Calorie (cal) which means that:

• When the value in terms of Calorie (cal) increases, then its value in Joule (J) increases at a rate of 4.2.

• When the value in terms of Calorie (cal) decreases, then its value in joules (J) decreases at a rate of 4.2.

Calories to Joules Formula

As you know, Calorie (cal) and Joule (j) are the most important physical quantities in physics. Hence, the conversion between Calorie and Joule and vice versa is crucial in solving Physics numerical. So scroll down to get the list consisting of various commonly used quantities.

Quick Grasp on Calorie to Joule Table

Do you Know?

We use calories in food instead of joules, and you will be able to know the answer by reading the text below.

1 joule is the work required to exert 1 Newton (N) force on a body for a distance of about 1 meter (m). Also, it equals the energy of 1 watt (W) of power for 1 second (sec).

A calorie is the amount of energy needed to raise 1 gram of water temperature by 1 degree Celsius.

So, it seems more logical to use calories based on its definition as a unit of energy; it seems to be more reliable to use it as a unit of energy in the case of food energy. A larger calorie is used as food energy.

Uses of Joule and Calorie

The concept of joules and calories is used in many fields. Some of them are as follows:

(i) Nutritional sciences

In the context of nutrition, calorie is the most commonly used unit of energy. Here, the larger calorie called the kilocalorie is used. Energy of a system/ component is measured as the number of kilocalories (kcal) of nutritional energy.

However, different physiologists and nutritionists in different parts of the world have different preferences; for example, in the United States, most nutritionists prefer the unit kilocalorie to the unit kilojoules, whereas most physiologists prefer to use kilojoules. In many countries of the world, nutritionists prefer the kilojoule to the kilocalorie. US food labeling laws (designed by USFDA) mandate the use of kilocalories (under the name of “Calories”); kilojoules are permitted to be included on food labels alongside kilocalories, but not required to do so. Contrary to this, in Australia, kilojoule is the officially preferred unit even when kilocalories, to some extent retains itself in popular use. 

In order to deal with misinterpretations between specific energy or energy density figures and energy; energy density is always quoted as “calories per serving” or “kcal per 100 g”, while nutritional requirements are often expressed in calories or kilocalories per day.

The major macronutrients in food (carbohydrate, protein and fat) contain 4 kilocalories per gram (carbs.), protein contains approximately 4 kcal/g  and 9 kcal in fats. Alcohol also has an energy value of 7 kcal/g. 

(ii) Chemistry

In other scientific fields, the term calorie almost always refers to the small calorie. and even though it is not an SI unit, it is still used in chemistry. For example, the
energy released in a chemical reaction per mole of reagent is sometimes denoted in kilocalories per mole. The main purpose here for the use of calorie was the ease with which it could be calculated in laboratory reactions, especially in aqueous solutions, for example,  when a volume of reagent is dissolved in water forming a solution, (concentration in moles per liter (1 liter weighing 1 kilogram)), it will induce a temperature change in degrees Celsius in the total volume of water solvent, that can be easily calculated in calories. It is also sometimes useful in specifying energy quantities related to reaction energy, such as enthalpy of formation and the size of activation barriers.

(iii) Measurement of energy content of food

The calorie, when defined  initially, was meant to specifically measure energy in the form of heat, especially in experimental calorimetry.

In many past experiments, a bomb calorimeter would be used to determine the energy content of food by burning a food sample and measuring the temperature change in the surrounding water. Today, this method has been replaced by calculating the energy content indirectly from adding up the energy provided by energy-containing nutrients of food (such as protein, carbohydrates, and fats). 

(iv) One joule represents many scientific measurements such as:

• The amount of electricity required to run a one watt device for 1 second or the energy required to bring an acceleration of one kg mass at 1 m/s² through a distance of 1 meter distance.

• In energy calculations, especially heat energy, it is measured as the energy required to raise the temperature 0.239 g of water from 0°C to 1°C, or from 32°F to 33.8°F.

• Another example is the typical energy that is released as heat by a person at rest every 1/60 s (17 ms) is one joule.

• The kinetic energy of a 2 kg mass traveling at 1 m/s is also one joule (based on calculations).