Definition of Heat: Formula, Capacity, Types, Transfers, and Example Questions

Meaning of heat – In physics lessons, the matter of heat must be familiar to Reader to discover and learn. Simply put, heat is one form of energy that can be received or released by things. Calories then use units of joules or calories that many people may already know. 

Are Reader still having trouble understanding caloric matter? No need to worry, Reader can read this article which discusses the complete matter of caloric, starting from formulas, types, transfer, and examples of caloric problems.  

Meaning of heat

In everyday life, Reader must be familiar with heat energy or heat energy, such as cooking or heating something. Well, that’s when there is a change in the temperature of the object where the heat has worked. The transfer of heat from one object to another can be in the form of conduction (conduction), radiation (radiation), and flow (convection).  

Heat is one of the forms of energy that can move from objects with a higher temperature to objects with a lower temperature if the two meet or come into contact. Two things that have different temperatures when they meet, heat will appear that flows or moves. For example, when Reader mixes cold water with hot water, then it will produce warm water. 

Reader need to know that temperature and heat are different. Temperature is a value that can be measured with a thermometer, while heat is energy that flows at the temperature of the object to another object. According to SI or MKS, the unit of calories is joule (J) while according to CGS, the unit of calories is erg and for some types of food, calorie units are used. It can be calculated that one calorie is the amount of heat energy required to raise the temperature of 1 gram of warm water to 1 degree Celsius (◦C). So it can be said that one calorie = 4,184 J or usually rounded to 4,2 J. 

The definition of heat can also be referred to as the heat energy possessed by a certain substance which to detect it requires the use of a temperature measuring device. Reader can notice that hot water that is left in the open air will eventually cool down because there is heat released from the water into the air. The things that can affect the increase and decrease in temperature of an object are the amount of heat, the mass of the object and the type of object itself. 

Heat will naturally move from an object with a higher temperature to an object with a lower temperature, so that it tends to equalize the temperature of the two objects if they meet or touch each other. If the temperature of an object is high, then the heat it contains is very large. On the other hand, if the temperature of an object is low, then the calories are low. So, it can be concluded that the amount of heat in an object or substance depends on 3 factors, namely the mass of the substance, the type of substance (specific heat), and the change in temperature. 

The heat can then raise or lower the temperature, so the greater the increase in temperature, the more heat is received. On the other hand, a small increase in temperature will make the calories received also small. That means, the relationship between heat (Q) will be directly proportional or proportional to the increase in temperature (∆ T), if the mass (m) and heat of the substance (c) of an object are constant.  

Caloric formula

Based on the definition of heat above, the following is a summary of the formulas related to heat material in Physics lessons:

1. Heat Transfer Formula

Q = mcΔT Description:

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Q = amount of heat received or released by a certain substance (J)

m  = mass of the object that receives or releases heat (kg)

c = substance type heat (J/kg⁰C)

ΔT = temperature change (⁰C)

2. Type Caloric formula

c = Q / m.ΔT Description:

c = substance type heat (J/kg⁰C)

Q = amount of heat released or received by an object (Joule)

m = mass of the object that receives or releases heat (kg)

ΔT = temperature change (⁰C)

3. Caloric Capacity Formula

C = Q / ΔT Description:

C = heat capacity (J/K)

Q = amount of calories (J)

ΔT = temperature change (K)

4. The formula for determining the caloric capacity itself

C = mc Description:

C = heat capacity (J/K)

M = mass of the object receiving or releasing heat (kg)

c = substance type heat (J/kg.K)

5. Formula of Heat of Fusion and Steam

Heat of fusion Q = mx L Heat of steam Q = mx U

provisions:

L = Heat of fusion of substance (Joule/kilogram)

U = Heat of vapor of substance (Joule/kilogram)

Types of Calories

Heat has several types that are categorized based on the process of working on certain substances. Here are the types of calories that Reader need to know in order to identify the changes in calories that occur in everyday life:

1. Heat of Formation (∆Hf)

The word formation heat is the heat that produces or is needed to make 1 mole of a compound in its elements, such as a gas written with its molecular formula. Examples of heat of formation are C12, O2, Br2, H2.  

2. Heat of Decomposition (∆Hd)

Decomposition heat is the form of heat produced or needed to decompose 1 mole of a compound into other elements. 

3. Burning Heat (∆Hc)

Combustion heat is the heat obtained or required to burn 1 mole of a substance, namely an element or compound. 

4. Heat of Neutralization (∆Hn)

Neutralization heat is the type of heat obtained or needed to form 1 mole of H20 from the reaction between acid and base. This heat is included in the exothermic reaction due to the temperature rise reaction. 

5. Heat of Solvation (∆Hs)

The heat of dissolution is the type of heat obtained or needed to dissolve 1 mole of a substance that was initially solid into a solution. 

Heat Types and Heat Capacity

Reader needs to know that it can also flow on two objects that have different substance particles and also different temperature companies. For example, when oil and water are heated to the same temperature, the temperature of the oil will experience a greater change than the change in water temperature. This can happen because there is a different type of heat between the objects that are put together or brought together. 

 

Specific heat is the amount of heat required to raise the temperature of 1 kg of mass to 1 ◦C. The unit of specific heat is calories/gram ◦celsius or in the international system it is determined using the unit Joule/kg ◦celsius. Every substance has a specific heat, each of which has a difference. Meanwhile, heat capacity is the amount of heat needed or absorbed to raise the temperature of certain substances to 1 ◦C. 

Caloric Change

In practice, heat works with the principle of changing two substances that meet or come into contact. Here are the heat changes that happen to substances when they are brought together or combined:

1. Heat Can Change the Temperature of Substances

Each object basically has a temperature lower than absolute zero, so the substance must have heat. This content will then make it the determinant of how much heat the temperature of the object has. If the substance is heated, it will receive additional heat until its temperature increases or increases. On the other hand, if the substance is cooled, it will release heat which causes its temperature to drop.  

2. Heat can change the form of matter

In some types of matter, if heat is given in a certain unit, then the matter will undergo changes. For example, ice that is heated or given heat will change its form from solid to liquid or gas. If the heating process is continued then the said water will change again into a gaseous substance. This happens when the substance that will change form from the liquid point to the melting point of the object. 

Various Heat Transfers

From the explanation of the meaning, type, formula, and change of heat above, it is clear that heat also moves when things come into contact or arrange. From that symptom, there are several types of heat transfer that can occur as follows:

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1. Conduction

The transfer of heat by conduction occurs by passing through an intermediate substance such as a metal without being accompanied by the permanent transfer of particles within the substance itself. For example, when you heat a metal end, the other metal end also heats up. This happens because of the transfer of heat from a high temperature to a lower temperature. 

Heating the metal tip will cause the metal particles to vibrate other particles connected to them. That is why all the metal particles will vibrate even if only one end of the metal is heated because this stimulates the transfer of heat. 

Other examples that occur in the type of conduction transfer are when holding firecrackers that are being burned, the exhaust of a motor becomes hot after the motor is turned on, the lid of a pot that heats up when used for cooking, butter that melts when heated, and so on. From the information above, the equation for heat transfer by conduction can be shown with the following formula: 

Heat Rate = Q/t = kA (T2 – T1)/x 2. Convection

Convection is one of the heat transfers that pass through a substance accompanied by the transfer of parts of the substances themselves. This transfer by convection can occur in liquid or gas, so this type of transfer is divided into two as follows:

  • Scientific Convection: Convection movement caused by buoyancy without external factors and influenced by differences in the types of objects. For example, what happens when heating water, where the specific mass of water particles that are already hot will rise away from the fire and then be replaced by other water particles that have a lower temperature. The process causes all the particles of the substance to be perfectly heated as a whole.  
  • Forced Convection: It is a convection transfer that occurs due to the influence of external factors such as pressure and heat transfer that occurs in a forced or intentional way. That means heat is forced to move to the destination with the help of external factors such as pressure. For example what happens to a fan that brings cold air to a hot place, a car radiator that has an engine cooling system, and other examples. 

Examples of convection transfer include, among others, the ups and downs of water when heated, the ups and downs of green beans when boiled, the occurrence of land and sea winds, the movement of hot air balloons, smoke from factory chimneys rising high into the air, and other examples. From the information above, it can be shown the equation for heat transfer by means of convection with the following formula: 

Heat Rate = Q/t = hA (T2 – T1)

3. Radiation

Radiation is the transfer of heat that does not use an intermediate substance at all. Radiation is not the same as conduction and convection in transferring heat. The transfer of heat by radiation does not always require the two objects to meet or come into contact with each other because the heat can be transferred without an intermediate substance. That means heat will be emitted in all directions by the heat source and then flow in all directions it can go. 

In fact, every object can emit and absorb heat radiation, but the amount depends on the temperature of the object and the color of the substance. The hotter the object is compared to the temperature of the surrounding environment, the greater will be the heat radiated to the surroundings. So the wider the surface of a hot object, the hotter the heat radiated to the surroundings. 

For example, what happened when Reader made a bonfire, then we would feel the warmth from the source of the fire at a certain distance. Reader must have felt the radiation of heat when the palm felt hot when faced with a light bulb that was burning. Another example that is most common is the heat from the sun that reaches the earth and other planets.  

From the information above, it can be shown the equation for heat transfer by means of radiation with the following formula: 

Heat Rate = Q/t = σeAT4 Due to the nature of heat that easily transfers, Reader can still prevent it from transferring easily. How to prevent heat transfer by conduction, convection, and radiation? Reader can insulate the room, like a thermos that functions to keep the water temperature warm by preventing heat transfer.